the planarians (turbellaria: tricladida paludicola) of lake...

The Planarians (Turbellaria:Tricladida Paludicola)

of Lake Ohrid in Macedonia

ROMAN KENK

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 280

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S M I T H S O N I A N C O N T R I B U T I O N S T O Z O O L O G Y • N U M B E R 2 8 0



Roman Kenk

SMITHSONIAN INSTITUTION PRESS

City of Washington

1978

A B S T R A C T

Kenk, Roman. The Planarians (Turbellaria: Tricladida Paludicola) of LakeOhrid in Macedonia. Smithsonian Contributions to Zoology, number 280, 56pages, 57 figures, 1978.—A revision is presented of the planarian fauna of theLake Ohrid area, known for its richness in endemic species with limited distribu-tion. Apart from the already known four endemic species of Phagocata and tenspecies of Dendrocoelum, six new species are described: Dendrocoelum decoratum,D. dorsivittatum, D. minimum, D. albidum, D. sinisai, and D. translucidum.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recordedin the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastreacavernosa (Linnaeus).

Library of Congress Cataloging in Publication DataKenk, Roman, 1898-The planarians (Turbellaria: Tricladida Paludicola) of Lake Ohrid in Macedonia.(Smithsonian contributions to zoology ; no. 280)Bibliography: p.Supt. of Docs. no. : SI 1.27:2801. Planariidae. 2. Dendrocoelum. 3. Dugesia. 4. Platyhelminthes—Ohrid Lake. I. Title.

II. Series: Smithsonian Institution. Smithsonian contributions to zoology ; no. 280.QL1.S54 no. 280 [QL391.P7] 591'.08s [595'.23'094976] 78-606202

Contents

Page

Introduction 1Family DUGESIIDAE 2

Dugesia Girard 2D. gonocephala (Duges) 2D. lugubris (O. Schmidt) 2

Family PLANARIIDAE 2Planaria Miiller 2

P. torva (Muller) 2Phagocata Leidy 2

P. ochridana (Stankovic and Komarek) 3P. stankovici (Reisinger) 6P. maculata (Stankovic) 6P. undulata (Stankovic) 8

Crenobia Kenk 9C. alpina montenigrina (Mrazek) 9

Polycelis Ehrenberg 9P. ten^s Ijima 9

Family DENDROCOELIDAE 10Dendrocoelum Orsted 10

D. adenodactylosum (Stankovic and Komarek) 11D. maculatum (Stankovic and Komarek) 14D. magnum (Stankovic) 16D. sanctinaumi (Stankovic and Komarek) 17D. komareki (Stankovic) 19D. decoratum, new species 20D. lacustre (Stankovic) 21D. dorsivittatum, new species 22D. lychnidicum (Stankovic) 23D. ochridense (Stankovic and Komarek) 24D. minimum, new species 27D. albidum, new species 28D. sinisai, new species 30D. translucidum, new species 31D. cruciferum (Stankovic) 33D. lacteum (Muller) 35D. jablanicense (Stankovic and Komarek) 37

Literature Cited 40Figures 42



Roman Kenk

Introduction

Lake Ohrid, situated in Macedonia astride thefrontier between Yugoslavia and Albania, occupiesa unique position among the lakes of Europe. It isa deep, ancient lake with an exceedingly richendemic fauna of a relict nature, which has sur-vived in the lake since the preglacial (Tertiary)period. A detailed discussion of the history, limnol-ogy, and biology of the lake has been presented bySiniSa Stankovid (1960) in his valuable monograph.

I studied the triclad fauna of the Ohrid regionseveral weeks in the summers of 1935 and 1937.Samples of some of the species were also takenalive to my laboratory at the University of Ljub-ljana, Yugoslavia, and were kept and observed therein cultures maintained at a temperature of 10° C.Work on the accumulated materials was interruptedby my change of employment, first to the Universityof Puerto Rico and then to the Library of Congressin Washington, D. C. My appointment as ResearchAssociate of the Smithsonian Institution enabledme to resume the long overdue work on the LakeOhrid collections.

In the following discussion of the individualplanarian species of the Ohrid region, I shall out-line and illustrate the external and anatomicalcharacters of each species, including those thatalready have been well described and analyzed inthe previous literature, particularly in the classicalpaper by Stankovid and Komarek (1927) and inlater additions by Stankovic (1938, 1969). Thus the

Roman Kenk, Department of Invertebrate Zoology, Smith-sonian Institution, Washington, D. C. 20560.

essential features of this very interesting planarianfauna, now scattered in the literature, will be foundcombined in one paper, and the new observationswill indicate possible variations in the appearanceof the anatomical characters that are so importantin the systematics of the group. The zoogeographicrelations and the questions of the historical originof the Ohrid fauna will not be repeated here, asthey have already been discussed in detail byKomarek (1953a) and Stankovic" (1932, 1960).

My studies of the Ohrid planarians were madeprincipally in the Bay of Ohrid in the northern partof the lake and in various tributary streams andtheir springs (see map, Figure 1).

With regard to the vertical distribution of thebenthic fauna of Lake Ohrid, particularly in itsnorthern part, the following ecological zones maybe distinguished (Stankovid, 1960:131-167): (1) anupper littoral zone or zone of water movementand/or emerging vegetation, from the water surfaceto a depth of 2-5 m; (2) a lower littoral zone, char-acterized chiefly by dense stands of several speciesof Chara, the Chara zone, at a depth of about5—20 m; (3) the sublittoral zone or shell zone(mainly Dreissena shells), extending from 20 m toabout 40-50 m; and (4) the profundal zone, belowthe shell zone to the bottom of the lake (286 m).

Specimens that are deposited in the NationalMuseum of Natural History (NMNH), SmithsonianInstitution, Washington, D.C., are listed under thecatalog numbers of the former United States Na-tional Museum (USNM).

ACKNOWLEDGMENTS.—I wish to express my deepindebtedness to my wife Ada, who assisted me very

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

ably in the field collections. My thanks are due toProfessor Sinisa Stankovic, then Director of theHydrobiological Station Ohrid, who kindly ex-tended to me the facilities of the station and per-mitted me the use of his personal boat in my work.Our stay at the station in 1937 was made even moreenjoyable by the presence of our dear friend Dr.Walther Arndt of the Zoological Museum of Ber-lin, whose tragic death in 1944 shocked the world-wide community of his colleagues. Mr. Ivan Znidarsicof Ljubljana prepared the watercolor paintings ofliving planarians reproduced in Figures 2-14. Dr.John C. Harshbarger and Mrs. Carolyn B. Gastof the Smithsonian Institution were helpful in thepreparation and arrangement of the illustrations ofthe paper. Dr. Marian H. Pettibone kindly re-viewed the paper for stylistic and topical errors. Iam grateful also to the publishers who permittedme to reproduce some figures from their publica-tions: Dr. W. Junk in The Hague, E. Schweizer-bart's Verlagsbuchhandlung in Stuttgart, andGustav Fischer Verlag in Jena.

Family DUGESIIDAE

The family Dugesiidae was first proposed by Ball(1971:24) in a section of his doctoral dissertationthat was later (1974) published. The family is toinclude the genera Dugesia, Cura, Bopsula, andpossibly Rhodax, which had previously been placedin the family Planariidae. The principal distinguish-ing character of the family is the opening of theoviducts, separately or after uniting, into the bursalstalk or rarely into the common atrium close to andposterior to the bursal stalk (Meixner's, 1928, typesI and II). In the Planariidae, the common oviductempties into the roof of the atrium (Meixner's typeIII). Ball (1974:376-378) subdivided the genusDugesia into several subgenera that he later (1976)elevated to the rank of genera. I agree with Ball'sseparation of the family Dugesiidae from thePlanariidae, but am not inclined to give the sub-genera of Dugesia a full generic status.

Dugesia Girard

Dugesia gonocephala (Duges)

MATERIAL DEPOSITED.—Sagittal serial sections of1 specimen on 3 slides, USNM 55294.

This species, widely distributed in Europe, hasbeen reported by Stankovic (1960:248) as occurringin running waters in the Ohrid region. I observedit in the spring Elesec, about 2 km north ofPestani.

Dugesia lugubris (O. Schmidt)

Stankovic (1960:248) states that this widely dis-tributed European species occurs in stagnant watersin the Ohrid area. I collected it in a drainage ditchat Teferit, west of Struga.

Family PLANARIIDAE

Planaria Miiller

Planaria torva (Miiller)

This is another eurythermic species with a widedistribution in Europe. Stankovic (1960:253) reportsthat one specimen was observed at the mouth of abrook at Studenciste, but none in the lake itself.I have not collected any mature specimens thatcould be assigned with certainty to this species.

Phagocata Leidy

The genus Phagocata in the wider sense, as indi-cated in my index (Kenk, 1974:40), is admittedly avery heterogeneous genus, widely distributed overthe Northern Hemisphere. Most of the species ofPhagocata described up to the early part of thiscentury were placed by their authors in the genusPlanaria. Komarek (1926a:9-10) was the first toattempt a subdivision of the European species ofthat genus when he arranged the representativesof Planaria into several genera and establish Fon-ticola and Albiplanaria for several white speciesof planariids in which the common oviduct opensinto the genital atrium; the male atrium is notsurrounded by radial muscle plates; and adeno-dactyls are lacking. Kenk (1930:293) and de Beau-champ (1932:272) did not accept Albiplanaria as aseparate genus and included it in Fonticola. Thegenus, as defined above, today comprises a greatnumber of species inhabiting Europe, Asia (includ-ing the Japanese islands), and North America. Hy-man (1937:302) pointed out that one of the Ameri-

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can species of the genus, Planaria gracilis Halcle-man, had been placed by Leidy (1847:248) into anew subgenus, Phagocata, which predates Komarek'sFonticola and should therefore be applied to allspecies placed into Fonticola. This suggestion wasfollowed by Dahm (1949), Gourbault (1972), andKenk (1974) but was objected to by several Euro-pean investigators, particularly Komarek (1953a:275) and Reisinger (1960:289-290).

It is true that the about 50 species, now includedin Phagocata because of the scheme of organizationof their reproductive systems, represent a greatvariety of external features as well as specific ana-tomical characters. It would be very desirable if onecould divide them at least into subgenera thatwould reflect natural (evolutionary) groups thatwould make sense also from a zoogeographicalstandpoint (see Ball, 1976:417-418). The threeNorth American polypharyngeal species (Phagocatagracilis, P. woodworthi, and P. nordeni) with almostidentical external habit but clearly different ana-tomical features, could be united in a subgenusPhagocata sensu stricto, as suggested by Reisinger(1960:290). Fonticola was used as a subgenus byGourbault (1972:29) who, however, did not formallydefine it. Atrioplanaria de Beauchamp (1932:334),with five or six European species, may be considereda valid genus because of morphological as well askaryological peculiarities (Gourbault and Benazzi,1977). Livanov and Zabusova (1940:96) establisheda separate genus Penecurva for four Asian speciesof different external aspects, in which the ejacula-tory duct opens on the ventral side of the penispapilla rather than on its tip. Such a condition isobserved also in several American species that havelittle else in common with the Asian forms. Thus,Penecurva is hardly tenable even as a subgenus.

When Fonticola is established formally as a sub-genus or genus with a clear definition, it will com-prise all Phagocata species of the Ohrid region,since the type-species of Fonticola, Planaria olivaceaO. Schmidt, 1961, is a member of this species group.

The European species of Phagocata, generallydesignated under Fonticola, eliminating Atrio-planaria, are very similar in their external appear-ance: unpigmented (white, with one exception),two-eyed planariids with a truncate head, lackingprominent auricular appendages and anterior ad-hesive organs. The interspecific differences concernmainly their anatomical characters. Reisinger (1960:

289-291), a meticulous investigator of this group,lists the following features as distinctive attributes:presence or absence of a spermatopositor (a Stifftube attached to the spermalophore); number andarrangement of the excretory pores; epithelial con-ditions at the transition from the copulatory bursato the bursa stalk; number of retinal clubs in theeyes; differences in the postembryonic developmentof the copulatory apparatus; and characteristicbehavior of the animals in the search for food orfor a copulatory mate. Not all these characters canbe identified in preserved specimens; some must beinvestigated in living animals by special techniques.

The following species may be considered to bewell established and readily distinguishable mor-phologically: Phagocata vitta (Duges), P. albissima(Vejdovsk^), P. olivacea (Schmidt), P. paravitta(Reisinger), P. bosniaca (Stankovic), P. undulata(Stankovic), and P. leptophallus (Reisinger). On theother hand, the affinities of four species, distributedchiefly on the Balkan Peninsula, P. macedonica(Stankovic), P. dalmatica (Stankovic and Komarek),P. ochridana (Stankovic and Komarek), and P.illyrica (Komarek), have been questioned, with goodreason, by de Beauchamp (1932), Dahm (1958, 1967),and even by one of their authors, Komarek (1953a:277; 1955:170). Not all the criteria enumerated byReisinger can be applied to these species. I shallretain them for the time being until further detailedinvestigations can be carried out.

Phagocata ochridana (Stankovic and Komarek)

FIGURES 15, 32

Fonticola ochridana Komarek, 1926a:9 [nomen nudum],Fonticola ochridana Stankovic and Komarek, 1927:643.Fonticola ohridana.—Stankovic, 1932:577.Fonticola albissima var. dalmatica.—de Beauchamp, 1932:319

[in part].Phagocata (? = Fonticola) ochridana.—Dahm, 1964:486.Phagocata (Fonticola) ochridana.—Gourbault, 1972:32.Phagocata ochridana.—Kenk, 1974:42.

MATERIAL DEPOSITED.—Sagittal serial sections of7 specimens on 9 slides, USNM 55299-55305.

A good description of this species was given byStankovic and Komarek, based on materials fromsprings and streams in the Ohrid region.

EXTERNAL FEATURES (Figure 15).—This is a ratherslender species, sexually mature specimens measur-ing up to 8 mm in length and 0.8 mm in width.


The anterior end is truncated, with a convex frontalmargin and rounded lateral corners. There is nonarrowing or neck behind the head. The lateralbody margins diverge only slightly behind the an-terior end, then run parallel up to the level of thecopulatory complex where they begin to convergeto form a bluntly pointed or nearly rounded tailend. The two eyes are far removed from the frontalmargin and lie close together at a distance of one-fifth to one-fourth the width of the head. The bodyis unpigmented, white. The pharynx is inserted atabout the middle of the body or slightly behindit and measures one-seventh the body length. Thecopulatory apparatus occupies the anterior two-fifths of the postpharyngeal region. The anteriorramus of the intestine ends at, or somewhat behind,the level of the eyes. The animals move by glidingonly, never by "crawling."

ANATOMY.—The testes extend from the level ofthe ovaries backward to near the posterior end.They are situated, in general, nearer to the ventralthan to the dorsal body wall, though a few testesmay be placed in a more dorsal position and indi-vidual testes may occupy almost the entire dorso-ventral diameter of the body. The structure andsituation of the ovaries show no pecularities. Vitel-laria or yolk glands are found in the mesenchymeof the entire body, except the head, and are par-ticularly numerous in the spaces lateral to the zoneof testes.

In the copulatory apparatus (Figure 32), thegenital opening leads directly into the genitalatrium which is not divided into the usual twochambers. In several specimens, however, histologi-cal differences were seen in the epithelium liningthe atrial cavity. The anterior part, which wouldcorrespond to a male atrium, had a normal, cuboidalor cylindrical, nucleate epithelium, while in theposterior section, the common atrium, the epithe-lium was infranucleate.

The size, shape, and position of the male copula-tory organ appear, in the majority of my specimens,as shown in Figure 32. The bulb of the penis is ofmoderate size and hemispherical. Its musculatureis rather weak, the muscle fibers being densest nearthe periphery of the bulb. The free penis or penispapilla is conical or finger shaped, somewhat curvedventrally, its pointed tip reaching to the dilatedgenital pore. The papilla is covered with a cuboidal

or flattened epithelium, beneath which is a well-developed layer of circular muscle fibers, followedby a thinner layer of longitudinal muscles. The twovasa deferentia enter the penis bulb laterally andacquire a coat of circular muscles. They first passtoward the midline of the organ, then turn pos-teriorly, enter the base of the penis papilla, andopen closely together, but separately, into the penislumen. This lumen is a straight canal, the ejacula-tory duct, running in the axis of the papilla andopening at its tip. Histologically, it is differentiatedinto three sections. A short anterior portion is linedwith very tall cells, the distal parts of which are bentposteriorly and form a villus or plug filling thelumen of the canal. This part has been likened toa seminal vesicle by Stankovic and Komarek. Thefollowing section of the canal has a rather flattenedepithelium, the cells of which are pierced by numer-ous gland ducts with a granular, strongly eosino-philic secretion. The third, most distal region ofthe penial lumen is usually somewhat widened andlined with taller cells with apparently secretoryfunction. It narrows again at the tip of the papilla.At least the anterior two sections of the penis lumenhave a thin coat of circular muscle fibers. A con-siderable variation in the length and shape of thepenis was observed even in animals collected in thesame locality. These differences are, undoubtedly,due to muscular contractions of the organ. The twomain muscular systems of the penis, i.e., the periph-eral layer of the penis bulb and the powerfulcircular muscles of the papilla, both effect, whencontracted, an elongation of the penis and its pro-trusion through the gonopore; much of the softparenchymal tissue of the bulb is pressed into thebase of the penis papilla. On the other hand, arelaxed state of the muscles will result in a shorterand broader shape of the organ; such a retracedpenis has a more voluminous bulb. The outer cover-ing of the papilla appears to be a cuboidal epithe-lium in the shortened penis, a flattened one in theelongated organ. The histological differentiationof the penial lumen is related to its function offorming a spermatophore during (or before?) copu-lation. The most anterior section, though it is notwidened in this species, may play the role of aseminal vesicle as Stankovic and Komarek (1927:625) assume. A comparison with closely relatedspecies indicates that the middle part of the lumen

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produces the chitinoid stalk or spermatopositor, andthe distal section the capsule of the spermatophore(cf. "Fonticola albissima var. illyrica" in de Beau-champ, 1932:317).

The two oviducts, running above the nerve cords,are equipped with accessory seminal receptacles ormodified yolk funnels, as Reisinger (1963:686-687)has demonstrated. In the region of the copulatorycomplex they ascend dorsally and medially, the leftone passing between the genital atrium and thebursal stalk. They unite dorsally to the atrium toform a rather long, somewhat curved common ovi-duct that opens into the posterior part of theatrium. The end parts of the paired oviducts andthe greater part of the common oviduct are con-nected with numerous eosinophilic shell glands.The copulatory bursa varies in size and shapeaccording to the state of maturity. Its lumen fre-quently contains remainders of one or more sper-matophores and/or spermatopositors. The bursalstalk proceeds from the bursa dorsally to the penis,then shifts to the left of the midline, increasinggradually in its outer and inner diameters, and joinsthe genital atrium from the left side near thegonopore. Sometimes a differentiation of the epi-thelium lining of the duct is seen. The anteriorpart, adjoining the bursa, always has a normal,nucleate, cuboidal epithelium, while the posteriorsection, connecting with the atrium, may showpartly or wholly infranucleate cells.

Numerous eosinophilic glands open into a largearea of the epidermis surrounding the genital aper-ture, the function of which is not quite evident.Their secretions may serve for the attachment ofthe egg capsules (cement glands) or else may playa role during copulation.

DISTRIBUTION AND ECOLOGY.—Phagocata ochri-dana occurs in the Ohrid region in a great varietyof habitats. Stankovid and Komarek found it origi-nally in springs near Sveti Naum and in the largelimestone spring Sum. Later, Stankovic (1934:167;1938:9; 1955b: 288) extended its known occurrencefirst to the littoral zone of Lake Ohrid and to lit-toral springs of Lake Janina (Ioannina) in theGreek Epirus, and then to the sublitoral and pro-fundal zones of Lake Ohrid. Obviously, Stankovic'sinterpretation of the species includes a form thatwas designated by Reisinger (1960:274) as a separatespecies, P. stankovici.

I collected Phagocata ochridana in the followinglocalities: StudenciSte, at the Hydrobiological Sta-tion, in cold springs and warmer pools, understones, and also on water plants; Bej-Bunar, north-east of the station, where it is rare in the cold springitself, more common in the creek and in ditcheswith warmer water, and under stones; a small springnear EleSec (north of the village of PeStani), to-gether with Dugesia gonocephala; springs at themonastery of Sveti Naum; spring Sum (about 1 kmsouth of Zagracani, near Struga), where the speciesis absent in the cold springs (8.2° C, 7 September1935) but occurs in warmer parts (up to 11.7° C),under stones; an irrigation ditch at Teferic, westof Struga; in Lake Ohrid, the species was foundin Ohrid Bay and near Kaliste from the shorelinedown to the shell zone.

A lot of Phagocata ochridana was cultured fortwo generations in the laboratory, with beef liveroffered as food. No asexual reproduction was ob-served in the cultures.

TAXONOMIC POSITION.—Phagocata ochridana wasfirst recorded by Stankovid (1926:238) as a conti-nental variety of P. olivacea (Schmidt). Stankovicand Komarek (1927:643) described it as a separatespecies. De Beauchamp (1932:319) considered it tobe a probable synonym of P. dalmatica (Stankovicet Komarek), which he cited as "Fonticola albissimavar. dalmatica." This assumption was accepted alsoby Komarek (1953a:278) and by the majority oflater authors who made reference to the species.On the other hand, Stankovic (1960:177) preferredto keep the species separate "for reasons of bio-geographical order." Reisinger (1963:687) pointedout that accessory seminal receptacles on the ovi-ducts have been found only in a few species of"Fonticola," F. ochridana, F. maculata, and F.leptophallus Reisinger, but apparently he did notexamine P. dalmatica for their occurrence. Rei-singer (1960:274) also separated from Stankovic'sP. ochridana a form inhabiting the deeper zonesof Lake Ohrid, which he designated as a newspecies, P. stankovici.

Considering that these three forms are still openquestions, for the time being I am keeping thecommon Ohrid Phagocata as a separate speciesto avoid a possible confusion when a more thor-ough comparison can be made, an investigationthat should include experiments on the possibilityof interbreeding. It seems to me quite probable that


all three will unltimately prove to be one species,Phagocata dalmatica (Stankovic and Komarek).

Phagocata stankovici (Reisinger)

FIGURES 13, 16

Fonticola stankovici Reisinger, 1960:274Phagocata stankovici.—Kenk, 1974:43.


This species was briefly characterized by Reisingeras differing from Phagocata ochridana by having aprecerebral extension of the intestine, without othermorphological data being given.

EXTERNAL FEATURES (Figure 13).—Phagocata stan-kovici is externally very similar to P. ochridana.It is somewhat smaller than the latter species, 5mm long and about 1 mm wide. The anterior endappears to be more rounded. The two eyes, sepa-rated from each other by about one-fourth thewidth of the head, are a little bigger than those ofP. ochridana. The end of the anterior intestinaltrunk forms an unbranched extension that reachesin the midline to a level anterior to the eyes. Thisseems to be the only essential external characterthat separates P. stankovici from P. ochridana. Thelength of the pharynx amounts to one-seventh thebody length, and the copulatory complex lies inthe anterior half of the postpharyngeal region.

ANATOMY.—All anatomical features recognizablein preserved specimens are identical with those ofPhagocata ochridana. I see no differences betweenthe two species in the configuration of the repro-ductive system, which makes a redescription hereunnecessary.

DISTRIBUTION AND ECOLOGY.—Several specimensof Phagocata stankovici were collected in OhridBay in the sublittoral (shell) zone at a depth ofabout 20 m, and one specimen was recovered fromtwo samples of mud dredged from 67 and 90 m,respectively. The statement by Stankovic (1955b:288) that P. ochridana inhabits all vertical zonesof the lake apparently includes P. stankovici underthat species.

Phagocata stankovici was kept in the laboratoryat 10° C on a diet of beef liver. The animals de-posited many spherical or slightly ovoid unstalkedegg capsules of 0.6-0.9 mm diameter.

TAXONOMIC POSITION.—It is with some reluc-

tance that I list Phagocata stankovici as a separatespecies different from P. ochridana. If the sole dis-tinguishing character is the extent of the anteriorintestinal ramus, it would not justify giving theform the rank of a species. In the American P.morgani (Stevens et Boring), the ramus extends toin front of the eyes in young specimens but endsbehind the eye level in the adults. It is true thatthe difference between P. stankovici and P. ochri-dana remains constant and unaltered in the labo-ratory cultures for several months. In Hymanellaretemiova Castle, belonging to a genus closely re-lated to Phagocata, individuals with precerebraland postcerebral gut trunks occur mixed in thesame population. It will be necessary to study thebehavior and possibly the karyological charactersof the two forms before arriving at a definitiveconclusion as to their status.

Phagocata maculata (Stankovic)

FIGURES 12, 22, 33

Albiplanaria maculata Stankovic, 1932:577.Fonticola maculata.—Stankovic, 1938:7.Phagocata (?«= Fonticola) maculata.—Dahm, 1964:487.Phagocata (Fonticola) maculata.—Gourbault, 1972:33.Phagocata maculata.—Kenk, 1974:42.


EXTERNAL FEATURES (Figures 12, 22).—Speciesis rather small, mature individuals having a lengthof 3-5 mm and a width of 0.75-1 mm. Stankovic(1938:7) estimated the size of living specimens fromhis preserved materials as being 6-8 mm, more thanI measured in living animals. The general shape ofthe body is similar to that of Phagocata ochridana.The frontal margin is somewhat more pointed thanin the latter species. It may be recalled that the out-line of the head in the different species of Phago-cata, as well as in other freshwater triclads, is subjectto considerable variation according to the physio-logical state of the animals, the temperature, andother environmental factors. If a cold-stenothermicanimal is examined in a dish with cold water that isgradually warming up during the time of observa-tion, certain changes in the behavior of the animalmay be noticed. It becomes rather active, glidesaround restlessly, performs searching movements,etc. During such increased activity, the anterior part

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of the body is sometimes excessively elongated andnarrowed. This fact makes it occasionally difficultto recognize the "normal" shape of the head andmay account for certain discrepancies in the de-scriptions of one and the same species given bydifferent observers or by the same observer at dif-ferent times. In P. maculata, no narrowing or neckbehind the head is seen. The two eyes lie closetogether at a mutual distance amounting to one-fourth to one-third the width of the head. The rootof the pharynx is anterior to the middle of the bodylength.

The outstanding characteristic of the species isthe pigmentation of the dorsal side. While the en-tire ventral surface, the head, and the marginalparts of the dorsal side are white, the middorsal areais pigmented in various ways. Usually there is onelarge spot of brown or almost black pigment somedistance behind the eyes (Figure 22A,C,D). Towardthe head and the lateral margins, the pigmentationgradually fades out, while a faintly brown middorsalpigment band extends toward the posterior end. Or,there may be a pair of spots in the prepharyngealregion, one on each side of the unpigmented mid-line (Figure 22B,E,F). The rest of the middorsal areabehind the spots may show just a touch of pigment,with the midline remaining white. The pigmenta-tion is granular, often cloudy or even spotty in ap-pearance. Stankovic (1938:7) indicated that the gen-eral color was light yellow and not white. Hisdescription, however, was made from specimens thathad been preserved for about 12 years. The yellow-ish ground color possibly was not natural or mayhave been due to the pale brownish tint of the mid-dorsal area.

ANATOMY.—The pigment of Phagocata maculataconsists of fine granules enclosed in the cells of themesenchyme underlying the layer of integumentalmuscles of the dorsal side. Only little pigment isseen between the muscle fibers.

The anatomy of the reproductive system links thespecies closely to the white phagocatas of the BalkanPeninsula. The distribution and arrangement of thetestes are the same as in P. ochridana and P. stank-ovici. In fully mature specimens, many testes extendthroughout the entire dorsoventral diameter of themesenchyme, as in P. stankovici. According to Rei-singer (1963:687), the oviducts in their anteriorcourse have accessory seminal vesicles similar tothose of P. ochridana.

The description and figure of the copulatory ap-paratus of Phagocata maculata by Stankovic (1938:7-8) are fairly accurate. There is no separate com-mon genital atrium developed, as the male atriumreaches to the gonopore. The penis has a small bulband a conical pointed papilla, somewhat curvedventrally (Figure 33). The layer of circular musclesunderlying the external epithelium of the papillais rather thick. The penial lumen is a straight tubein the axis of the papilla, formed by the union ofthe two vasa deferentia (vd) and showing the samethree sections as in P. ochridana: an anterior section(vs), only slightly widened, filled with a plug ofelongated cells, representing the seminal vesicle; atubular middle section, receiving the outlets ofeosinophilic gland ducts, presumably the sectionforming the spermatopositor of the spermatophore;and a distal section of somewhat wider diameter,lined with taller cells and opening at the tip of thepapilla. I was not able to see a small diverticulumor cul-de-sac at the anterior end of the penial lumenas illustrated by Komarek (1953a, fig. IK,).

The copulatory bursa (b) in some of my speci-mens contained remains'of spermatophores. Its out-let, the bursal duct (bd), opens into the genitalatrium from the left side, close to the genital pore.Its anterior section is lined with a normal nucleateepithelium, its posterior part with an infranucleateepithelium.

DISTRIBUTION AND ECOLOGY.—Phagocata is a com-paratively rare species inhabiting the sublittoralshell zone of Lake Ohrid. Stankovic originally col-lected 8 specimens in Ohrid Bay from depths of 25-35 m. My materials of about 20 specimens weredredged in the same locality at depths between 18and 30 m. One immature individual, kept in alaboratory culture, reached sexual maturity.

TAXONOMIC POSITION.—Both Stankovic (1938:7)and Komarek (1953a:277) stressed the similarity ofthe anatomy of Phagocata maculata with that ofP. macedonica or P. illyrica, and Komarek expressedthe opinion that P. maculata might be interpretedas being a small depth race ("Tiefenrasse") of thewhite P. illyrica. Since the extent and intensity ofthe pigmentation of P. maculata shows an exceed-ingly wide range of variation, I am inclined to at-tribute only a subordinate taxonomic value to thischaracter. Nevertheless, in view of the gaps in ourknowledge of its behavior, life history, and karyo-

8 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

logical and genetic conditions, I am keeping ittentatively as a separate species.

Phagocata undulata (Stankovic)

FIGURES 23, 28A,B, 34

Fonticola undulata Stankovic, 1960:178.Phagocata (?«.Fonticola) undulata.—Dalim, 1964:487.Phagocata (Fonticola) undulata.—Gourbault, 1972:33.Phagocata undulata.—Kenk, 1974:43.


Phagocata undulata has been known only from afigure by Stankovic (196oTl77, fig. 68b,).

EXTERNAL FEATURES (Figure 23).—Mature ani-mals attain a length of 8 mm and a width of 2 mm.The species is characterized by a strikingly beautifulshape that is unique not only among the representa-tives of the genus Phagocata, but among the fresh-water triclads in general. The lateral margins of thebody are thrown into almost regular, wave-likecurves and folds that give them a peculiar scallopedappearance. The number of folds on either side isfrom six to eight, in nearly symmetrical arrange-ment. The inner margins of the folds extend overthe dorsal surface of the body. Except on the frontaloutline of the head and the tip of the posterior end,the margin has a row of short conical papillae. Thecurves and folds are constant features and are dis-tinct in resting as well as gliding animals. Theyshould not be confused with the transitory wavyruffles that appear in many planarians, particularlyin dendrocoelids, when the body is contracted dur-ing "crawling" movement or at rest. The frontalmargin of the head is more or less rounded or formsa blunt angle at the anterior tip. The body is wid-est at about the region of the pharynx. The poste-rior end is usually pointed during locomotion. Theanimal is unpigmented, white, and rather trans-parent. The two eyes are situated very close to-gether at a distance of about one-sixth the width ofthe head, and removed from the frontal margin.The pharynx lies approximately at the middle ofthe body or somewhat behind it. The intestine isclearly visible in the living animal because of thetransparency of the body. The anterior intestinalramus ends at the level of the eyes and bears oneach side four to five lateral branches, which them-selves are ramified. Each posterior ramus has many

small lateral branches and several short medialbranches. The animal moves exclusively by "glid-ing," never by "crawling."

ANATOMY.—The usual smooth, ciliated epithe-lium is found only on the ventral surface of thebody, covering the area that is in contact with thesubstrate (Figure 28B). The entire dorsal surfaceand the folds and papillae of the marginal regionare covered with a modified epithelium consisting ofconical or hemispherical cells lacking cilia (Figure28A). Each cell contains a large number of smallrhabdites surrounding the nucleus. Another typeof epithelium occurs along the frontal margin ofthe head, forming a narrow strip to either sideof the midline, immediately above the submarginalzone of adhesive cells. This epithelium is ciliated,infranucleate, and contains very few small rhab-dites. Apparently the two strips represent the auric-ular sense organs.

In the reproductive system, the numerous testeslie predominantly close to the ventral side of thebody. Only few are situated more dorsally, particu-larly in sections where the testes are very crowded.The testicular zone begins immediately behind theovaries and extends posteriorly almost to the tailend.

The copulatory organs (Figure 34) correspondclosely to the scheme characteristic of the Balkanicrepresentatives of the genus Phagocata. The genitalpore (gp) leads into a relatively small commonatrium (ac) that connects anteriorly with the maleatrium (am), the two chambers not being markedoff distinctly. The penis consists of a rather smallbulb and a conical papilla. The musculature ofthe bulb is weak, developed mainly near its periph-ery. The papilla, on the other hand, possessespowerful muscles arranged in a thick layer of cir-cular fibers and a thinner one of longitudinalmuscles beneath the outer epithelium. The two vasadeferentia (vd) approach the ventral part of thepenis bulb, penetrate it in a medial direction, thenturn dorsally and open into the moderately widelumen of the penis. This lumen is divided histolog-ically into three sections, as is the case also in P.ochridana and P. maculata. At the openings of thevasa deferentia, the epithelium of the lumen con-sists of very tall cells that are directed toward thepapilla and form a plug filling the lumen. Posteriorto the plug, the ejaculatory duct (de) is lined witha flatter epithelium that is pierced by numerous

NUMBER 280

eosinophilic gland ducts. Great masses of theirsecretion are found in the tissues surrounding thisregion, in the parenchyma of the penis bulb, andadjoining parts of the papilla, particularly in theventral half of the organ. This secretion is appar-ently used in the formation of the spermatopositorof the spermatophore. The third section of thepenial lumen is usually somewhat widened, linedwith a taller epithelium, and opens into the atriumat the tip of the penis papilla.

The two oviducts unite dorsally to the maleatrium forming the common oviduct (ode) thatopens into the atrium. The end parts of the pairedoviducts and the upper three-fourths of the commonoviduct are equipped with shell glands. The copula-tory bursa (b) sometimes contains remnants of sper-matophores. The stalk of the bursa (bd) runs some-what left of the penis, starting from the bursa as anarrow canal, then curving ventrally while grad-ually becoming wider, and opening into the com-mon genital atrium from the left side. A largenumber of eosinophilic gland ducts (gl) open in thearea surrounding the genital pore.

ECOLOGY AND DISTRIBUTION.—A total of 32 speci-mens of Phagocata undulata were collected in Au-gust 1937 in Ohrid Bay by dredging at depthsbetween 16 and 26 m in the shell zone of the sub-littoral. All animals were small, generally about 3mm long, and immature. They were placed in aculture maintained at a temperature of 10° C andfed beef liver. They grew and developed sexualstructures after several months. Several cocoonswere laid and many young hatched between Janu-ary and May 1938, after which the culture wasdiscontinued. No reproduction by fission occurredin the culture. The fact that only immature animalswere collected in August may indicate that repro-duction in the lake takes place at some other sea-son, possibly in winter or spring.

Two specimens were observed in copula. Theyrested at the bottom of the culture dish, parallel toeach other, both heads pointing in the same direc-tion The anterior parts of their bodies were at-tached to the substrate, while the posterior partswere twisted in such a way that the ventral surfacesof the two animals were pressed against each other.When the animals were pulled apart, the two penescould be seen protruding from the genital pores.

TAXONOMIC POSITION.—The peculiar differentia-tion of permanent folds and papillae along the

margin of the body is not duplicated in any otherspecies of freshwater planarians so far known. Pha-gocata papillifera (Ijima and Kaburaki) of Japan hasa linear series of 20 to 25 small papillae along themiddorsal line. Numerous papillae spread over thedorsal surfaces are known to occur in two species ofLake Baikal in Siberia, Sorocelis leucocephala Zabu-sov and Planaria papillosa Korotnev, both nowplaced in the genus Papilloplana (= ThysanoplanaGraff, not Plehn). In an earlier paper (Kenk, 1930:148), I expressed my doubts as to the taxonomicvalue of projections on the body surface (papillae,etc.). Phagocata undulata fully confirms this opin-ion. The anatomical structure of the species en-tirely conforms with the scheme observed in thegenus Phagocata and, moreover, the species is moreclosely related to the Balkanic representatives of thegenus than to the remaining Phagocata species ofthe Eastern and Western Hemispheres. In partic-ular, it is the detailed structure of the male copula-tory organ that resembles closely that of P. ochri-dana and related forms. Phagocata undulata is,therefore, despite its striking external habit, a typi-cal member of the genus Phagocata.

Crenobia Kenk

Crenobia alpina montenigrina (Mrazek)

MATERIAL DEPOSITED.—Sagittal serial sections of1 specimen on 3 slides, USNM 55252.

This polypharyngeal subspecies of the widelydistributed alpine planarian, found in many placesin the Balkan Peninsula, is a cold-stenothermicform inhabiting springs and streams in the Ohridregion. Stankovic and Komarek (1927:647) foundit in the large spring Sum and in the outlet of LakeOhrid, the river Drim. It is very numerous in thespring Bej-Bunar, where it occurs in the companyof Dendrocoelum maculatum, D. sanctinaumi, D.adenodactylosum, D. jablanicense, Phagocata ochri-dana, and Polycelis tenuis. I collected it also inSum, together with four endemic Ohrid species ofthe genera Dendrocoelum and Phagocata, and inthree small springs near Velestovo.

Polycelis Ehrenberg

Polycelis tenuis Ijima

MATERIAL DEPOSITED.—Sagittal serial sectionsof 2 specimens on 3 slides, USNM 55312-55313.


This ubiquitous eurythermic European species,generally inhabiting stagnant waters, was observedin the Ohrid region in several streams (but neverin Lake Ohrid): in the creek Kulincivljik na Sinoruat the town of Ohrid, also in Bej-Bunar, and atStudenciSte.

Family DENDROCOELIDAE

Dendrocoelum Orsted

The dendrocoelids of Lake Ohrid were firstplaced into a new genus, Neodendrocoelum, estab-lished by Komarek (1926a: 7), who listed amongtheir distinguishing characteristics the large size ofthe adenodactyl (which is larger than the penis)and the configuration of the atrial cavity. This cav-ity consists of two compartments: a long cavitynamed "atrum genitale," which contains the papillaof the penis and receives the mouth of the com-mon oviduct in its posterior part; and a compart-ment designated as "atrium copulativum," enclos-ing the papilla of the adenodactyl and connectingwith the opening of the bursal stalk. These twocavities unite only near the genital pore. No "atriumcommune" is developed. The species have one pairof eyes and are either white or pigmented.

Stankovic and Komarek (1927:596-598) men-tioned the same characteristics of the genus andadded that the penis has a wide lumen and thatits papilla may be invaginated, resembling a fla-gellum.

Kenk (1930:300) included Neodendrocoelum inthe genus Dendrocoelum and distinguished onlytwo subgenera, Dendocoelum sensu stricto andParadendrocoelum, which differ in the course oftheir oviducts.

Later authors have not accepted Kenk's subdivi-sion of the genus Dendrocoelum. De Beauchamp(1931:157; 1932:207-208), who studied the genusmost intensively based on copious material, dividedit into eight subgenera. He accepted Neodendro-coelum as a subgenus of Dendrocoelum after somehesitation, but stated that it was not clearly separa-ble from the subgenus Dendrocoelides. He added tothe characteristics of the subgenus the presence ofa glandular field around the genital opening andpeculiarities in the histology of the oviducts. Heexcluded one of the Ohrid species, N. jablanicense,from Neodendrocoelum and placed it in the sub-

genus Eudendrocoelum with a question mark. Gour-bault (1972), the latest reviser of the genus Dendro-coelum, followed essentially de Beauchamp's ar-rangement.

Komarek (1953a:303) accepted the status of Neo-dendrocoelum as a subgenus of Dendrocoelum andalso included Dendrocoelum subterraneum, a blindspecies described earlier from a cave in Croatia.

Stankovic (1960:178-179, 263), in evaluating thetaxonomic rank of Neodendrocoelum, repeated thepreviously enumerated characters of the taxon andconsidered it "more prudent to keep Neodendro-coelum provisorily as a distinct genus preciselybecause of its peculiar geographic distribution."

Reisinger (1971:117-119) discussed the interrela-tionships of the various genera or subgenera of theDendrocoelum group. He came to no conclusionabout the definite rank of Neodendrocoelum, butwas inclined to consider it an acceptable genus.

It is very difficult to establish clear criteria forthe demarcation of Neodendrocoelum from otherspecies groups of the Dendrocoelum complex. Thedivision of the genital atrium into two compart-ments, the genital and copulatory atria, is seen alsoin other members of the subgenus Dendrocoelides,where the cavities are generally designated as themale and the common atria. The relative sizes ofpenis and adenodactyl are subject to great variationwithin the genus and cannot be used as an impor-tant systematic character. The glandular fieldaround the gonopore may be seen also in otherspecies of the genus, perhaps to a lesser degree, andit is also not prominent in all Ohrid species.

In view of this complex situation, I prefer toleave the question of the validity of Neodendro-coelum, even as a subgenus, open to further investi-gations. New criteria may possibly be found in theanalysis of the chromosome morphology or inbiochemical studies of the species concerned.

As has been pointed out very appropriately byKomarek (1953a:303; 1953b:269), the copulatoryapparatus of a great number of the species of Den-drocoelum of the Ohrid region exhibits a surpris-ing conformity, which would make it very difficultto identify the individual species by its anatomyalone. Variations within the apparatus are oftenonly of a quantitative nature or are due to variousstates of muscular contraction, stages of sexual ma-turity, or employment of different fixing agents.It is, therefore, necessary to look for other charac-

NUMBER 280 11

ters as well, such as the general proportions of thebody, the exact shape of the anterior end, the situa-tion and arrangement of the testicles, the develop-ment of the subepidermal musculature, the be-havior of the animal in life, and the pattern ofpigmentation. Pigmentation is generally consid-ered to be a rather variable and taxonomically notvery reliable character. Nevertheless, it is the mostobvious and most easily recognizable feature of theOhrid species.

Species that were available to former workersand to the present writer in sufficient numbers tobe observed and analyzed intimately are undoubt-edly good species. Among these I would countDendrocoelum maculatum, D. sanctinaumi, D. jab-lanicense, D. magnum, D. ochridense, D. cruci-ferum, D. lacustre, and D. translucidum. Of the un-pigmented white species, D. adenodactylosum isobviously very near to D. nausicaae, which is moregenerally distributed in southwestern Europe butmay be distinguished by karyological characters,according to Stankovic (1969:427). Dendrocoelumjablanicense clearly differs from the rest of theOhrid dendrocoelids by the deviating anatomy ofits copulatory complex. The whitish D. albidumand D. sinisai differ from all other species of theOhrid area by having a distinctive invaginatedadhesive organ. Their mutual relationship, how-ever, needs to be investigated on more material.Among the pigmented species of the lake, severalforms inhabiting the sublittoral and profundalzones show a variable number of light spots ar-ranged in a pair of rows on the dorsal surfaces, buthave been examined in only a few specimens. Theydiffer from each other chiefly by the number andoutline of the spots. As we lack sufficient informa-tion on the effects of environmental parameters onthe color pattern of these forms, it is possible thatthey may in part be referable to species occurringin the littoral or in the tributaries of the lake.Among these are D. komareki, D. decoratum, D.dorsivittatum, "Neodendrocoelum sp. 3" of Stanko-vic (1955a, pi. 5: fig. 7), and a few other formsobserved occasionally but not described in thispaper. Two other species, D. cruciferum and D.lacustre, both from the shell zone of the lake, aresomewhat similar in their color pattern, consistingof a median pigment stripe and a pair of darkspots on the dorsal surface. They differ, however,so markedly in the shape of the anterior end, their

size, and behavior that their specific identity cannotbe doubted.

Some of these open questions may be solvableby karyological, by biochemical studies, or by aninvestigation of the possibility of interbreeding ofthe forms concerned.

Dendrocoelum adenodactylosum (Stankovicand Komarek)

FIGURES 5, 24, 26, 35, 52A,B

Neodendrocoelum adenodactylosum Stankovic and Komarek,1927:599.

Xeodendocelum nausicae.—Stankovic, 1930:168 [in part].Dendrocoelum (Neodenrocoelum) adenodactylosum.—de

Bcauchamp, 1931:157.

MATERIAL DEPOSITED.—Sagittal and transverseserial sections of 7 specimens on 22 slides, USNM55253-55259.

Dendrocoelum adenodactylosum is the most com-mon triclad of the Ohrid region, occurring both inLake Ohrid and in its. tributary streams and sources.It was first described by Stankovic and Komarek(1927:599-603). In later publications, beginningwith 1930, Stankovic considered the species to beidentical with D. nausicaae O. Schmidt (1861), aspecies originally discovered in several localities ontwo Ionian islands, Corfu (Kerkyra) and Cephalonia(Kephallenia), off the west coast of Greece.Schmidt's figures and anatomical analysis of thecopulatory organs of his species were surprisinglyaccurate for his time, considering that the observa-tions were made on whole animals. Many yearslater, Wilhelmi (1909:4) collected additional speci-mens from Schmidt's original localities, which wereexamined by Komarek (1925:326-328), Stankovicand Komarek (1927:617-620), and by de Beau-champ (1932:219-222). Komarek (1953a:305) him-self collected the species again on the island ofCorfu; D. nausicaae proved to be widely distributedin southeastern Europe (Balkan Peninsula, Austria,Italy) and even in Asia Minor. De Beauchamp(1932:208, 219) treated D. adenodactylosum and D.nausicaae as separate species and, in a later paper(1937:357), pointed out the differences betweenthem (see also Gourbault, 1972). More recently,Stankovic (1969:427) came to the same conclusion,chiefly on the basis of differences in the chromosomenumbers of the two forms. Reisinger (1971:133) also


considered D. adenodactylosum to be a separatespecies, though closely related to D. nausicaae.

EXTERNAL FEATURES (Figures 5, 24).—The shapeof the animal in life was discussed by Stankovicand Komarek. The species is unpigmented, white,and its appearance is similar to that of Dendro-coelum lacteum. According to Stankovic, the ani-mals attain a length of 20 mm and a width of3.5-5 mm. De Beauchamp reported that specimensfrom Sum measured less than 10 mm, but thisobviously refers to preserved worms. I have seensexually mature specimens that in life were only16 mm long and 2.5 mm wide. The anterior endis truncated, the frontal margin bulging anteriorly.To either side of the frontal margin is a roundedlobe, projecting somewhat laterally. When the ani-mal glides along undisturbed, a faint, but usuallywell discernible, narrowing or neck is seen, separat-ing the head from the rest of the body.

There are normally two eyes, situated approxi-mately at the level of the neck. The distance be-tween them is slightly more than one-third thewidth of the neck and their distance from thefrontal margin is greater than that from the lateralmargins. Supernumerary eyes are not rare and mayoccur anteriorly as well as posteriorly to the prin-cipal eyes. Occasionally one finds specimens thathave up to four eyes on each side, arranged in acurved longitudinal row (Figure 26), as has alreadybeen observed by de Beauchamp (1937:357).

The intestine is usually well visible in the livinganimal, particularly from the ventral side. The an-terior ramus reaches up to the level of the eyesand bears 9-12 branches on each side. The twoposterior rami, with up to 18 branches each, usuallyunite behind the copulatory apparatus.

The pharynx is inserted at about the middle ofthe body in sexually mature specimens, its lengthamounting to one-seventh the body length. Thecopulatory apparatus occupies the anterior half ofthe postpharyngeal region.

The animal moves generally by gliding. Uponstimulation, a "crawling" locomotion may be in-duced, in which the subterminal adhesive organis used for successive attachment to the substrate.This crawling is less jerky than that of D. lacteumand is sustained only for a short time. During crawl-ing and when the animal is at rest, the lateral mar-gins of the body form wavy folds.

ANATOMY.—The anterior adhesive organ is

moderately developed. It is situated in the midlineon the ventral side of the frontal margin and con-sists of a well-circumscribed area of infranculeateepithelial cells pierced by eosinophilic gland ducts.Fibers of the ventral subepidermal longitudinalmuscle layer attach to the adhesive area, but nospecial muscular differentiations are developed. Theorgan is larger than that of D. jablanicense, but farless conspicuous than the adhesive cushion of D.lacteum. The median diameter of the adhesive sur-face is about 150 ̂ ra.

The anatomy and histology of the reproductivesystem of D. adenodactylosum has been discussedin detail by Stankovic and Komarek (1927:599-602)and by de Beauchamp (1932:208-211; 1937:357). Iam giving here only the essential features of thissystem and am adding figures of the copulatoryapparatus that will show the appearance of thiscomplex in various states of contraction and relaxa-tion of its organs. The testicles are numerous andessentially ventral. They occupy a broad zone oneither side, which extends from the level of theovaries to close to the posterior end. The widenedanterior end or tuba of each oviduct, adjoiningthe ovary and functioning as a seminal receptacle,appears at full maturity as a large rounded sacwith a tall epithelial lining, the tubal bursa, quitesimilar to that described by de Beauchamp (1932:212) for D. maculatum (see also Reisinger, 1963:684). This tubal bursa serves for the resorption ofsuperfluous sperm and is found also in other speciesof dendrocoelids of Lake Ohrid.

In the copulatory apparatus (Figure 35), theadenodactyl (ad) is very large and situated to theleft of the midline; the penis is smaller and locatedon the right side and rather far dorsal. The sizeand shape of the atria may vary considerably dueto the state of contraction or expansion of theadenodactyl. The male atrium, designated by Stan-kovic and Komarek as the genital atrium, is ratherlong and is lined with a thick epithelium, the innerborder of which is packed with eosinophilic secre-tion granules. The penis may assume differentshapes. In the majority of the preparations itappears as shown in Figure 35: a penis bulb ofmoderate size, enclosing a slightly widened cavitywith a thick epithelial lining, the seminal vesicle(vs), receiving close to its anterior end the separateopenings of the vasa deferentia (vd); the penispapilla shows a more or less distinct division into

NUMBER 280 13

two parts, a basal part with thick walls, coveredby a rather tall surface epithelium, beneath whichis a strong layer of circular muscles; and a distal,thin-walled part with hardly any muscle fibers, con-taining a usually rather wide lumen. In other speci-mens the penis may be completely extended (Figure52A; see also de Beauchamp, 1932, fig. xxiv): in thiscase the bulb is extremely contracted, the seminalvesicle pushed into the base of the papilla, thepapilla itself appearing tube shaped, tapering indiameter toward its tip. In the other extreme (Fig-ure 52B), a complete introversion of the papillainto the bulb may occur: the bulb then appearsexpanded, its wall rather thin, its lumen volumi-nous, the openings of the vasa deferentia placed farapart, the papilla assuming the shape of an invertedpseudoflagellum. The statement by Reisinger (1971:133) that D. adenodactylosum differs from D. nausi-caae by the fact that it normally (in life) has noinvaginated pseudoflagellum, while D. nausicaaeregularly shows such an invagination, may beerroneous.

The two oviducts unite behind the copulatoryapparatus after embracing the bursal duct. Thecommon oviduct (ode) thus formed is rather shortand opens into the caudal part of the male atrium.The bursa (b) and the bursal stalk (bd) show nopeculiarities. De Beauchamp observed a connectionof the bursa with intestinal caeca that approachit from both sides. He did not see any continuity ofthe cavities of the bursa and the caeca. Neverthe-less he interpreted these connections as virtualgenitointestinal communication. I have repeatedlyseen intestinal branches approaching or even touch-ing the bursa laterally. This is, however, by nomeans a constant feature. I would hesitate to con-sider this connection a functioning communicationbetween bursa and intestine. The bursal duct (bd)proceeds from the bursa posteriorly above orslightly to the left of the penis and graduallywidens, then turns ventrally and opens into thecommon atrium (Komarek's "copulatory atrium").The anterior part has a very fine cover of musclefibers, which thickens in the posterior part andbecomes rather conspicuous just before the mouthof the duct. This terminal portion of the musclecoat, consisting principally of circular fibers, is the"sphincter" mentioned by de Beauchamp (1932:211; 1937:357).

The adenodactyl (ad) is unusually large and con-

tains a long lumen that may expand to a cavityof irregular outline in the bulb of the organ. Itsshape varies from a long, slender, somewhat curvedorgan to a pear-shaped one with almost sphericalbulb. It is obvious that these different shapes de-pend mainly on the state of contraction of its mus-cular systems. The papilla is always bent but maybe pointing in various directions. When the organis elongated, the papilla protrudes posteriorly andextends the wall of the common atrium abnormally(see Stankovic and Komarek, 1927, text-figure 2); inother cases it is inserted into the end portion of thebursal duct (Figure 35), protrudes through thegenital aperature (de Beauchamp, 1932, fig. xxiv),or may penetrate into the male atrium.

The glandular field of tall epidermal cells sur-rounding the gonopore, considered by de Beau-champ (1931:158) to be a distinguishing character-istic of the subgenus Neodendrocoelum, is welldifferentiated at full sexual maturity.

DISTRIBUTION AND ECOLOGY.—Dendrocoelum aden-odactylosum is a very common inhabitant of coldsprings and streams of the Ohrid region. I col-lected it in the spings of Studenciste, Bej-Bunar,Sveti Naum and Sum and in Kulincivljik na Sinoru,a small stream near the western border of the townof Ohrid. Stankovic and de Beauchamp likewiseobtained most of their animals from springs, andexpressly mention StudenciSte, Sveti Naum, Sum,and Gradiste, the latter being a small tributary ofDrim River (which is the outlet of Lake Ohrid).Stankovic and Komarek reported that the speciesis common also in the littoral zone of the lake. Ina later paper, Stankovic (1934:176) stated that thelittoral animals are usually asexual during the sum-mer. I found, however, both mature and immaturespecimens in the littoral zone, particularly amongthe dense vegetation of reeds near the Hydrobio-logical Station. Stankovic and Komarek also re-ported the species from the profundal zone at adepth of 108 m. It is highly probable that thisrecord concerns D. sinisai rather than D. adeno-dactlyosum. The latter species occurs also in LakePrespa, a nearby lake southeast of Lake Ohrid(Stankovic, 1969:428).

Dendrocoelum adenodactylosum can easily bekept in the laboratory. Beef liver is readily takenas food. In one culture, cocoons (spherical and un-stalked) were deposited and young animals hatched.

TAXONOMIC POSITION.—The history of the dis-


covery of D. adenodactylosum has been discussedin the introductory paragraph to the species. Itsclose relationship to D. nausicaae is undeniable (seealso Komarek, 1953a:305-306). Nevertheless, I agreewith the opinion of de Beauchamp and of Rei-singer: of keeping the two forms as separate species,particularly because of the karyological differencesbetween them, as mentioned by Stankovic (1969:427). In a recent paper, Paunovic (1977) establishedthe chromosome number of D. adenodactylosum tobe 2n = 32, while that of D. nausicaae is 2n = 14.

Dendrocoelum maculatum (Stankovicand Komarek)

FIGURES 2, 36, 54

Neodendrocoelum maculatum Stankovic and Komdrek, 1927:603.

Neodendrocoelum spec, (immaturum I) Stankovic and KoinA-rek, 1927:621.

Dendrocoelum (Dendrocoelum) maculatum.—Kenk, 1930:301.Dendrocoelum (Neodendrocoelum) maculatum.—de Beau-

champ, 1931:157.Dendrocoelum maculatum.—Kenk, 1974:18.


EXTERNAL FEATURES (Figure 2).—Illustrations ofthe external aspects of the species in life were givenby Stankovic and Komarek (1927:604) and byStankovic (1955a, pi. 4: fig. 1). Mature animalsare 15 to 25 mm long and 3 to 4 mm wide. Duringundisturbed gliding, the frontal margin of the headshows three distinct lobes: a broad, curved, medianlobe and a pair of smaller, rounded, lateral lobeswell marked off from the median lobe. Behind thehead, a slight constriction or neck is visible. Pos-teriorly to this, the lateral margins of the bodydiverge gradually until the greatest width is at-tained at about the middle of the body length orsomewhat behind it, then converge again in thelast quarter of the body and meet at the moderatelypointed posterior end. In gliding locomotion, themargins are smooth, but during crawling movementthey are thrown into folds and ruffles. The shapeof the anterior end also changes constantly in thecrawling animal, the median lobe being now re-tracted, now excessively protruded.

The two eyes are situated far apart, their dis-tance from each other amounting to about one-half

the width of the head at the level of the eyes. Themouth is situated somewhat behind the middle ofthe body and the genital aperture is closer to themouth than to the tail end.

The most distinguished character of the speciesis the pattern of its coloration. The dorsal surfaceis a variable shade of brown (olive brown, reddishbrown, chocolate brown, or almost black) with alighter (yellowish or grayish) pattern. The lightcolor forms a narrow rim along the lateral margins,except on the lateral lobes of the head; a triangularfield on the head extends from the middle lobebackward beyond the level of the eyes; there arecharacteristic spots to each side of the midline ina longitudinal row of 6 to 8 that have an irregularlobed and branched outline. In the gliding animal,these spots appear elongated longitudinally. Theyfrequently show a tendency to fuse to a netlikepattern. A pair of indistinct light dashes extendsfrom the lateral lobes of the head obliquely back-ward and medially, which probably corresponds tothe location of the auricular sense organs. Usuallythere is also a more or less marked light band inthe middorsal line. On closer examination, it con-sists of a double row of small elongated splashesalong the midline of the prepharyngeal region, apale, somewhat broader spot above the pharynxand copulatory complex, and a distinct medianband in the hindmost part of the body. The ventralsurface is likewise pigmented, but much lighter,almost uniformly yellow or yellowish brown, witha lighter area below the pharynx and another sur-rounding the genital pore.

In young animals, the pattern of the dorsal sur-face is simpler, the lateral spots being less branched,often almost round. The shape of the anterior end,however, is typical and the characteristic light tri-angular field on the head is always distinct.

ANATOMY.—The pharynx is relatively long, aboutone-seventh the body length. The adhesive cushion,situated on the underside of the median frontallobe, is a rather large field of modified epitheliumwith eosinophilic gland ducts, measuring 180-290/xm in median diameter.

The reproductive system of Dendrocoelum macu-latum has been described well by Stankovic andKomarek (1927:603-605) and de Beauchamp (1932:212-215). I shall give here only the essential char-acters of the system.

The numerous small testes are located both dor-

NUMBER 280 15

sally and ventrally to the intestine and at immediatelevels between the intestinal branches. The tes-ticular zone extends from the region of the ovariesbackward close to the posterior end.

The genital pore (Figure 36, gp) is surroundedby an area of very tall epithelial cells, characteristicof several related species of the Ohrid region. Itmeasures 36-60 /im in thickness, while the generalepithelium of the ventral surface is 17 /im andthat of the dorsal surface 25 /xm thick. The cellsin this area lack rhalxlites and are pierced by agreat number of parallel gland ducts (gl), the cellbodies of which are situated in the mesenchyme ofthe ventral side, above the layers of the integu-mental muscles of the genital region. In prepara-tions fixed by de Beauchamp's fluid (ethanol,formalin, and acetic acid), the secretions of theglands are dissolved and the gland ducts appearempty. Worms killed with mercuric chloride solu-tion show the secretion in the canals to be homoge-neous, staining pink with erythrosin. It is difficultto establish the homology of these peculiar glands,as de Beauchamp (1932:219) points out. They seemto correspond to glands found in various tricladsand designated by Meixner (1928) as "Kittdriisen"(cement glands), though this name might properlybe restricted to glands that empty into the commonatrium.

The genital pore leads into the common atrium(ac), which encloses the free papilla of the adeno-dactyl and connects with the stalk (bd) of thecopulatory bursa and with the more or less elon-gated male atrium (am).

The penis lies to the right side of the midline.Its bulb is large, but not very muscular. Whenextended, the penis papilla is conical and some-what irregular in outline (Figure 36). It is coveredby a cubical or columnar epithelium pierced bynumerous gland ducts that carry a grandular secre-tion staining in various shades of red with erythrosin.Beneath the epithelium is a layer of circular musclefibers, strong and thick in the basal half of thepapilla, but very thin in the distal part. The widecavity in the penis bulb, the seminal vesicle (vs), islined with an epithelium that forms villuslike pro-jections. The two vasa deferentia (vd) open sepa-rately into the anterior part of the vesicle from thesides. The cavity continues into the penis papilla,forming a wide canal with uneven outline thatopens at the tip of the papilla. Many gland ducts

(pink after staining with erythrosin) empty into thepenis lumen, at least into its anterior part. Thepenis papilla can be partly invaginated into thepenis lumen. Then the penis bulb appears to bedistended and the seminal vesicle very voluminous(Figure 54). Only the distal part of the papilla, thatis the part lacking the thick muscle layer, is in-versible, while the basal portion remains protrudinginto the atrium.

The two oviducts unite behind the copulatoryapparatus, embracing the bursal duct. The longcommon oviduct (ode) runs, to the right side ofthe bursal stalk, almost horizontally forward andopens into the end part of the "male" atrium.

The copulatory bursa (b) is a large sac extendingfar laterally (however, not occupying the entirewidth of the body, as Stankovic" and Komarek indi-cate). The ratio between its transverse and antero-posterior diameters is approximately 3:1. The bursais often lobate, with irregular outline. De Beau-champ stated that a pair of outgrowths of the bursaapproach the vasa deferentia; these outgrowths,however, are not always present. In one case healso observed an open communication between thesperm ducts and the bursa, through which spermwere passing. I have never seen such a communica-tion in my preparations and must assume that whatde Beauchamp saw was an accidental rupture of thewalls of the two organs.

The bursal stalk or duct (bd) starts from theposterior wall of the bursa as a rather narrow canalsituated to the left of the penis, then widens trans-versally to a flat sac above the common atrium.From this flattened portion, a short wide canal pro-ceeds ventrally and opens through the roof of thecommon atrium. This canal is surrounded by athick layer of muscle fibers. The widening of thebursal stalk and the sharp bend it undergoes abovethe common atrium are particularly characteristicof the species.

The adenodactyl (ad) is large and usually exceedsthe penis in size. It lies to the left side of the mid-line.

DISTRIBUTION AND ECOLOGY.—Dendrocoelum mac-ulatum was collected by Stankovic and Komarek inseveral tributary streams of Lake Ohrid (at Stu-denciste and Sveti Naum) and in the large springSum (west of Struga). De Beauchamp examined ani-mals from springs near Sveti Naum and near Tuse-imiSte (Albania). Immature specimens were re-


ported from the littoral of the lake, particularlyin the Bay of Ohrid. My own material was collectedin Bej-Bunar, StudenciSte, Sveti Naum, and Sum.In these cold habitats, the worms may be found insummer and probably the year round in all stagesof development. They are more numerous in thequiet parts of the streams and rare or entirely absentin the springs themselves. The species is also verycommon in the littoral zone of the lake, understones, among algae, and on high plants; however,no sexually mature animals can be found thereduring the summer months or in early autumn. Asthe color pattern of the young specimens is some-what different from that of the adults, their iden-tity with the animals living in cold streams was notrecognized at first by Stankovic and Komarek, whodescribed the littoral form as "Neodendrocoelum$p£c.?-(immaturum I)." Mature specimens withtypical coloration were found in the lake in winter,however (Stankovic, 1938:6). I kept several indi-viduals of the immature shore form in the labora-tory at low temperature and they developed thetypical spotted pattern of the adults. There can beno doubt that the animals from the two types ofhabitat are identical.

I collected Dendrocoelum maculatum in the lakein shallow water near the town of Ohrid (watertemperature in August, 24.7°C), near Studenciste,near Velidab (in the vicinity of a submerged spring,10.9°G), and at Kaliste. De Beauchamp reports italso from Struga and Lin. It was occasionally foundin the lower littoral (Chara zone) in Ohrid Bay, ata depth of 10 m, and at Kalis'te, 7-13 m.

Reisinger (1963:684-685) reports to have collectednear Graz, Austria, a planarian that is anatomicallyidentical with D. maculatum, particularly in thedevelopment of large tubal bursae and yolkfunnels. The only difference from the Ohrid formis its complete lack of body pigment, though theeyes are developed normally. He referred to thespecies first as "Neodendrocoelum ad maculatum,"later as N. maculatum, and considered the lack ofpigment to be no taxonomically valid characteristic.The identical species was reported later by An derLan (1964:479) from the Danube River in Austria.If this form had been observed in the Ohrid area,it would undoubtedly have been described as aseparate species, as it is well known that severalspecies in that area can hardly be separated byanatomical characters (see Komarek,, 1953b:269),

although they differ in their pigment patterns,behavior, and preferred type of habitats. In lightof this situation, I would prefer to consider theunpigmented form preliminarily to be at least aseparate subspecies for which I propose the nameDendrocoelum maculalum candidum. Further in-vestigations will be necessary to determine its rela-tion to the Ohrid form, such as a karyologicalanalysis and, particularly, a study of the possibilityof interbreeding of the two forms.

In the laboratory, Dendrocoelum maculatum mayeasily be kept in culture on a diet of beef liver.Cocoons laid in the aquaria were round or bluntlyellipsoidal and unstalked (smallest cocoon spherical,with a diameter of 1.7 mm; largest one ellipsoidal,with diameters 2.6 and 2.3 mm).

TAXONOMIC POSITION.—In the structure of thecopulatory apparatus, Dendrocoelum maculatum isvery similar to other pigmented species of the Ohridregion, D. ochridense and D. lacustre, which caneasily be distinguished by their characteristic colorpatterns, body shape, some histological features, andbehavior. From D. sanctinaumi, which shows asomewhat similar pigment design, D. maculatumdiffers by its slender proportions, the shape of theanterior end (the lateral lobes being marked offfrom the median lobe), the position of the eyes(farther apart), and by the shape of the dorsal spots.Preserved specimens of D. maculatum are usuallyelongated, frequently rolled in toward the ventralside, with the lateral margins ruffled, while inD. sanctinaumi the body remains broad and flat,with concave ventral and convex dorsal sides, andthe body margins smooth (see also Stankovic andKomarek, 1927:609, and de Beauchamp, 1932:216).Paunovic and Rimsa (1968) and Paunovic (1977)investigated the chromosome set in the testes andovaries of D. maculatum, and they determined thechromosome numbers to be n=16, 2n=32.

Dendrocoelum magnum (Stankovic)

FIGURES 10, 37

?Neodendrocoelum sp. 4 Stankovic 1955a, pi. 5: fig. 8.Neodendrocoelum grande Paunovic and Rimsa, 1968:413

[nomen nudum].Neodendrocoelum magnum Stankovic, 1969:414.Dendrocoelum {Neodendrocoelum) magnum.—Gourbault,

1972:70.Dendrocoelum magnum.—Kenk, 1974:18.

NUMBER 280 17


This is a rather common species of the shell zoneof Lake Ohrid.

EXTERNAL FEATURES (Figure 10).—The speciesis characterized by having a thick and bulky body,not as flattened as the similar D. sanctinaumi orD. maculatum. My specimens measured up to 22mm in length and 6 mm in width. According toStankovic, they may attain a length of 26 mm atfull maturity. The anterior end is truncate witha very slightly bulging frontal margin and roundedlateral corners. Behind the head is only a slightindication of a neck constriction. The posteriorend is rather bluntly pointed. The pigmentationof the dorsal side consists of a dark grayish-brownground color, which fades out toward the bodymargins, and a pair of longitudinal rows of pro-fusely branched whitish or light yellowish spots,8-12 in each row. An indistinct light brown striperuns along the dorsal midline, widening somewhatabove the pharynx. On either side of the head isseen a short unpigmented streak, apparently cor-responding to the auricular sense organs. Theventral surface is a dirty white or light yellow.

The two eyes are rather close together, at a dis-tance of about one-fourth the width of the head.Their distance from the frontal margin is less thanthat from the lateral margins.

The locomotion of the animal is by a slow glid-ing, rarely by crawling movements.

ANATOMY.—The adhesive organ is a small (upto 170 fim in diameter) subterminal field of in-franucleate epithelium in which the eosinophilicadhesive glands open and to which a few longi-tudinal fibers of the ventral subepidermal musclelayer are attached.

Unfortunately, I had no fully mature specimensof Dendrocoelum magnum at my disposal, only afew individuals in which the reproductive organswere in the anlage stage. For the analysis of thereproductive system we have, therefore, to relyon Stankovic's (1969:414-417) detailed description.The zone of rather small testes extends from thelevel of the ovaries to the posterior end. The testesare indicated as being predominantly dorsal (how-ever, I observe also many testicular anlagen in theventral parts of the mesenchyme in my specimens).The oviducts are equipped with well-developedyolk funnels and their anterior enlargements ad-

joining the ovaries show large typical tubal bursae.The adenodactyl and bursal duct are situated to theleft, the penis to the right of the midline. Thegenital pore is surrounded by a field of epidermispierced by numerous eosinophilic glands. The penisis shown in Stankovic's figure (see Figure 37) as arounded bulb with a large spherical cavity, intowhich a rather folded penis papilla is completelyinvaginated. The long male atrium connects withthe common atrium close to the gonopore, receiv-ing the common oviduct in its terminal part.

DISTRIBUTION AND ECOLOGY.—Dendrocoelum mag-num is a common species essentially confined to thesublittoral (shell zone) of Lake Ohrid. My speci-mens were dredged from depths between 19 and 30m in Ohrid Bay, always associated with Dreissena,which appears to be their natural food. Stankovicreported its occurrence at depths of 20-50 m andstated that it deposits its cocoons of 3.5-4 mmdiameter on dead Dreissena shells. The species maybe kept in the laboratory at 10°C on a diet of beefliver and also tolerates temperatures above 20°C,according to Stankovic.

TAXONOMIC POSITION.—Dendrocoelum magnumagrees with the other pigmented species of Dendro-coelum of the Ohrid area in all its anatomicalcharacters. From the similar D. maculatum andD. sanctinaumi, it differs by the bulkiness of itsbody and the pigmentation pattern of the dorsalside, as well as by the different ecological habitat.Paunovid and Rimsa (1968) analyzed the chromo-somes of "Dendrocoelum grande" and found theirnumber to be 2n = 32. One of the authors (D.Paunovid) informed me that the species was D.magnum, still undescribed at the time of theirpublication. A detailed analysis of the chromosomemorphology was given by Paunovic (1977).

Dendrocoelum sanctinaumi (Stankovicand Komarek)

FIGURFS 3, 38, 55

Neodendrocoelum St. Naumi Stankovic and Komarek, 1927:609.

Neodendrocoelum spec.—(immaturum II) Stankovic andKomarek, 1927:622.

Dendrocoelum (Dendrocoelum) st.-naumi.—Kenk 1930:300.Dendrocoelum (Neodendrocoelum) Sancti-Naumi.—de Beau-

champ, 1931:157.Neodendrocoelum Sancti Naumi.—Komarek, 1953a:303.Neodendrocoelum svetinaumi.—Geus, 1967:253.



Descriptions of Dendrocoelutn sanclinaumi werepresented by Stankovic and Komarek (1927:609-613) and by de Beauchamp (1932:216-219).

EXTERNAL FEATURES (Figure 3).—The species iscomparatively short and broad, mature individualsattaining a maximum length of 15 mm and a widthof 4 mm. The anterior end is truncate, with abulging frontal outline that forms an indistinct,very blunt, median point in the quietly glidinganimal. The rounded lateral lobes are not markedoff from the central region of the frontal margin.Behind the head is an indistinct trace of a neckconstriction. The lateral margins then diverge verygradually to reach the maximum width at aboutthe posterior third of the body length. The tail endis bluntly pointed. At rest, the animal assumes abroad, ovoid shape.

The two eyes lie rather close together at a dis-tance of about one-third (or less) the width of thehead. The mouth is situated a little behind themiddle of the body, the genital pore halfway be-tween the mouth and the posterior end.

The ground color of the dorsal surface is brown,varying in shade from a light grayish-brown toalmost black. The light, yellowish color patternresembles that of Dendrocoelum maculatum: itforms a rim along the margins of the body; a streakalong the midline, beginning at the anterior pointof the head, narrowing behind the eyes, wideningagain in the regions of the pharynx and thecopulatory complex, and ending at the posteriortip; and a row of four to six lobed or irregularlybranched spots in the lateral fields on each side ofthe midline. These spots are, in general, wider andless ramified than in D. maculatum, extending morein a transverse direction. They may, though rarely,show a tendency to fuse longitudinally. A pair ofshort oblique splashes above the lateral lobes ofthe head mark the position of the auricular senseorgans. The ventral surface is uniformly gray.

Dendrocoelum sanctinaumi is slower and lessactive than D. maculatum. Its locomotion is eithergliding or crawling. Already Stankovic (1960:260)observed that D. sanctinaumi usually contracts andremains still upon mechanical stimulation, whileD. maculatum tries to escape by rapid crawlingmovements.

ANATOMY.—The anterior adhesive organ is veryweak, forming a small subterminal spot, 70-100 /anin diameter, no longer than the width of the lateraladhesive zone from which it is separated by a smallgap on either side. The pharynx is short, its lengthamounting to one-ninth or one-eighth the lengthof the body in preserved specimens. The ratio be-tween the width and the length of the pharynx is1:1.1 or 1:1.6.

The reproductive system of Dendrocoelum sanc-tinaumi has been analyzed in detail by Stankovicand Komarek and by de Beauchamp. The rathersmall testes are situated in the ventral, dorsal, andintermediate parts of the mesenchyme, extendingfrom the level of the ovaries posteriorly to aboutmidway between the gonopore and the tail end.The copulatory organs (Figure 38) are very similarto those of D. maculatum, with only some quantita-tive differences. The genital pore is surrounded bya circular area of modified epithelium with manygland ducts (gl), analogous to that described forD. maculatum. The general arrangement of theparts of the copulatory apparatus is the same asin the latter species, the adenodactyl and bursalstalk lying somewhat to the left and the penis andcommon oviduct to the right of the midline. Thepenis and the adenodactyl are of approximatelyequal size. In most specimens, the penis papilla (pp)is elongated, filling the entire male atrium (am),sometimes reaching down to the genital aperture.The penial lumen is a wide duct running from thebulb to the tip of the papilla. Its anterior portionmay be somewhat expanded and is lined with ataller epithelium through which gland ducts open.This portion receives the separate openings of thetwo vasa deferentia (vd) and corresponds to aseminal vesicle (vs). The posterior part of thelumen, lined with a more flattened epithelium, maybe considered to be a modified ejaculatory duct.In one of the eight animals examined, however, thedistal part of the papilla was inverted into thelumen of the penis (Figure 55). It is possible thatthe inverted position is the normal condition inthe living animal and that the eversion and elonga-tion of the penis is brought about by a contractionof the muscles in the wall of the penis bulb whenthe animal is being killed. The arrangement of themuscles and glands of the penis is similar to that ofD. maculatum.

From the junction of the two oviducts behind the

NUMBER 280 19

copulatory complex the common oviduct (ode)passes anteriorly to the right of the bursal stalkand connects with the posterior part of the maleatrium (am). The copulatory bursa (b) has arounded or more or less lobate outline. The bursalduct or stalk (bd) widens somewhat above the com-mon atrium (ac) but is not as excessively broadenedand flattened as in D. maculatum. It curves ven-trally to open into the common atrium.

ECOLOGY AND DISTRIBUTION.—Stankovic andKomarek collected mature specimens of Dendro-coelum sanclinaumi only in running water, insprings near the monastery of Sveti Naum. Imma-ture animals were found also in the littoral zoneof the lake but were rarer than D. maculatum. DeBeauchamp's material also comprised mature indi-viduals from Sveti Naum and a few immaturespecimens collected near the shore of the lake atthe towns of Ohrid and Struga. In later papers,Stankovic (1955a:491; 1969:430) reported its occur-rence also in the sublittoral zone. I found D. sanc-tinaumi to be fairly common in cold streams alongthe east side of the lake: Bej-Bunar, StudenciSte,and Sveti Naum. It occurs usually under stones,frequently in a strong current, often resting (feed-ing?) on small snails. As a rule, it is absent in thesprings themselves and appears in the streams atsome distance from their source. In the lake itself,the species occurs from the littoral zone down tothe shell zone but is nowhere common. Some speci-mens collected in summer in the shell zone of OhridBay (at depth from 16 to 26 m) were sexually ma-ture. From these data we may conclude that £>.sanctinaumi attains maturity in the cold habitats(streams, deeper zone of the lake) at any time ofthe year; in the littoral waters, which warm upconsiderably in the summer months, it apparentlydevelops genital organs only during the colderseason (see also Stankovic, 1969:430). It is, however,a eurythermal species and may be maintained inthe laboratory for months at a temperature above25°C (Stankovic, 1934:175).

I have kept D. sanctinaumi in laboratory culturefor prolonged periods at 10°C. The animals re-fused to take beef liver as food and diminished insize. It is possible that aquatic snails are theirnormal food, as they are often associated with themin their natu

the planarians (turbellaria: tricladida paludicola) of lake...

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