milnesium zsalakoae and m. jacobi, two new species of tardigrada (eutardigrada: apochela:...

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Milnesium zsalakoae and M. jacobi, two new species ofTardigrada (Eutardigrada: Apochela: Milnesiidae) from thesouthwestern United StatesAuthor(s): Harry A. Meyer and Juliana G. HintonSource: Proceedings of the Biological Society of Washington, 123(2):113-120.2010.Published By: Biological Society of WashingtonDOI: http://dx.doi.org/10.2988/09-29.1URL: http://www.bioone.org/doi/full/10.2988/09-29.1

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Milnesium zsalakoae and M. jacobi, two new species ofTardigrada (Eutardigrada: Apochela: Milnesiidae) from

the southwestern United States

Harry A. Meyer* and Juliana G. Hinton

(HAM, JGH) Department of Biology and Health Sciences, McNeese State University,

Lake Charles, Louisiana 70609, U.S.A., e-mail: [email protected]

Abstract.—Two new species of the phylum Tardigrada belonging to the

genus Milnesium are described. Two specimens of Milnesium zsalakoae, newspecies, were collected from foliose lichens on rocks in Arizona and New

Mexico, U.S.A. and mounted in Hoyer’s medium. Milnesium zsalakoae has

primary claw branches of great length and slenderness, substantially longer

relative to the length of the buccal tube than those of any other species of

Milnesium. Eleven specimens of Milnesium jacobi, new species, were found

in foliose and fruticose lichens collected in eastern Texas, U.S.A. and

mounted in Hoyer’s medium or polyvinyl lactophenol. Milnesium jacobi

differs from all species of Milnesium in having a very broad, cylindricalbuccal tube and in the posterior placement of its stylet support insertions.

The eutardigrade family Milnesiidae

currently consists of three genera and 15

recent species (Table 1), and Milnesium

swolenskyi Bertolani & Grimaldi, 2000, a

Cretaceous species. One cosmopolitan

species, Milnesium tardigradum, has been

reported on all continents. Most of the

remaining Recent species are known only

from their type localities; however, Lim-

menius porcellus, Milnesioides exsertum,

and Milnesium asiaticum have been found

at several sites. Distribution of all species,

except Milnesium tardigradum, is restrict-

ed to a single biogeographic region: six

are Palearctic, two are Afrotropical, two

are Neotropical, and New Zealand, Aus-

tralia, Antarctica, and the Nearctic each

have one species (Table 1). Tardigrades in

the family Milnesiidae have mostly been

collected from mosses and lichens on

trees, rocks, or the ground (Table 1).

Only two species have been collected

from aquatic samples or soil.

This paper describes two new species in

the genus Milnesium from the southwest-

ern U.S.A.

Materials and Methods

Foliose and fruticose lichens collected

in Texas, Arizona, and New Mexico were

soaked overnight in tap water and exam-

ined with a stereoscopic microscope.

Tardigrades were mounted on slides in

Hoyer’s medium or polyvinyl lactophenol

and examined with phase contrast mi-

croscopy.

All measurements are given in micro-

meters (mm). Claw terminology and claw

measurements follow Tumanov (2006).

The pt index (Pilato 1981) is the ratio,

expressed as a percentage, of the length of

a structure to that of the buccal tube (in

the description of the type specimens the

pt index for a structure is given after its

measurement, in square brackets and

italics). Buccal tube length was measured

from the anterior boundary of the stylet* Corresponding author.

PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON123(2):113–120. 2010.

sheath to the base of the tube; stylet

support insertion is the distance to the

insertion point of the stylet supports from

the anterior end of the buccal tube.

Buccal tube width was measured as the

external diameter of the buccal tube at the

insertion of the stylet supports. Lengths

of the main claw branches were measuredfrom the base to the apex, including

accessory points. The bb index in Milne-

sium is the ratio of the length of the claw

base + secondary branch to the length of

the basal spur (Tumanov 2006).

Holotypes and paratypes of both spe-

cies are deposited in the W.A.K. Seale

Museum (WAKSM), McNeese State

University, Department of Biology and

Health Sciences, Lake Charles, Louisiana,

U.S.A.

Taxonomic Account

Class Eutardigrada, Richters, 1926

Order Apochela Schuster, Nelson,

Grigarick, & Christenberry, 1980

Family Milnesiidae Ramazzotti, 1962

Genus Milnesium Doyere, 1840

Milnesium zsalakoae, new species

Figs. 1, 2

Material examined.—Holotype: from

foliose lichen on rock, FR 545, SunsetCrater Volcano National Monument, Ar-

izona, U.S.A. (35u219500N, 111u319250W;

elev. 2100 m), 9 Apr 2001, WAKSM slide

9350. Paratype: from foliose and crustose

lichens on cedar tree (Cedrus sp.), Mile

Marker 6, Highway 60W, New Mexico,

U.S.A (34u139420N, 108u509410W; elev.

2200 m), 8 Apr 2001, WAKSM slide 9351.

Table 1.—Distribution of Tardigrada in the family Milnesiidae. Location information taken from original

descriptions, except for M. tardigradum, see McInnes (1994).

Species Substrate Location Biogeography

Limmenius porcellus Horning,

Schuster & Grigarick, 1978

tL South Island, New Zealand NZ

Milnesioides exsertum Claxton, 1999 rL, rM New South Wales, Tasmania,

and Victoria, Australia

Au

Milnesium almatyense Tumanov, 2006 tL Almaty, Kazakhstan P

Milnesium antarcticum Tumanov, 2006 aM King George Island, Antarctic An

Milnesium asiaticum Tumanov, 2006 gM Chui Area and Osh Area,

Kirghizia

P

Milnesium brachyungue Binda &

Pilato, 1990

L Punta Arenas, Chile Nt

Milnesium dujiangensis Yang, 2003 M Sichuan Province, China P

Milnesium eurystomum Maucci,

1988 (1991)

rL, rM Kiagtut Sermiat Glacier,

central Greenland

Na

Milnesium katarzynae Kaczmarek,

Michalczyk & Beasley, 2004

gtM Sichuan Province, China P

Milnesium krzysztofi Kaczmarek &

Michalczyk, 2007

M Costa Rica Nt

Milnesium longiungue Tumanov, 2006 rM, rL Himachal Pradesh, India P

Milnesium reductum Tumanov, 2006 rM Jalal-Abad Area, Kirghizia P

Milnesium reticulatum Pilato,

Binda & Lisi, 2002

M Alphonse Island, Seychelles Af

Milnesium tardigradum Doyere, 1840 L, M, S Cosmopolitan Af, An, Au, I,

Na, Nt,

NZ, O, P

Milnesium tetralamellatum Pilato &

Binda, 1991

M Ngorongoro, Tanzania Af

Substrate and biogeographic abbreviations. Substrates: a 5 aquatic, g 5 ground, L 5 lichen, M 5 moss,

r 5 rock, S 5 soil, t 5 tree; Biogeographic regions: Af 5 Afrotropical, An 5 Antarctic and subantarctic,

Au 5 Australian, I 5 Indomalayan, Na 5 Nearctic, Nt 5 Neotropical, NZ 5 New Zealand, O 5 Oceania,

P 5 Palearctic.

114 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON

Diagnosis.—Smooth cuticle. Accessory

points on main branches absent. Basal

spurs present on all claws. Main claw

branches very long, slender (pt of all main

claw branches .64, of leg III .80, of leg

IV .94).

Description.—Holotype: body length

477.0 (Fig. 1A). Body white or transpar-

ent, cuticle smooth. Prominent eyes in

lateral position (Fig. 1B). Buccal appara-

tus with six peribuccal papillae, two

lateral papillae, and six peribuccal lamel-

lae. Buccal tube 36.5 long and 15.3 [41.9]

wide. Stylet supports inserted on buccal

tube at 24.9 [68.2]. Claws of Milnesium

type (Fig. 2A–C). Claw bases + secondary

branches slender, with well-developed

basal spurs. Main claw branches slender

and long, lacking accessory points

(Figs. 1B, 2B, C). Internal claw lengths:

leg I main branch 23.5 [64.4], claw base +secondary branch 12.0 [32.9], basal spur

5.4 [14.8]; leg II mb 23.6 [64.7 ], cb + sb

13.7 [37.5], bs 5.6 [15.3]; leg III mb 29.4

[80.5], cb + sb 12.8 [35.1], bs 6.0 [16.4 ]; leg

IV mb 34.6 [94.8], cb + sb 16.8 [46.0], bs

6.7 [18.4]. Slender transverse cuticular

bars on first three pairs of legs.

Paratype: body length 480.2. Buccal

tube 28.0 long and 10.3 [36.8] wide. Stylet

supports inserted on buccal tube at 19.9

[71.1]. Internal claw lengths: leg I mb 19.2

[68.6], cb + sb 12.7 [45.4], bs 4.8 [17.1]; leg

II mb 22.5 [80.4], cb + sb 15.9 [56.8], bs 6.5

[23.2]; leg III mb 24.8 [88.6], cb + sb 13.5

[48.2], bs not measurable; leg IV mb 28.8

[102.9], cb + sb 13.6 [48.6], bs 3.1 [11.1].

Other characteristics as for holotype.

Eggs unknown.

Etymology.—The specific name honors

the first author’s mother, Rose Zsalako

Meyer, in recognition of her selfless sup-

port of his academic and scientific career.

Discussion and differential diagnosis.—

Milnesium zsalakoae differs from all other

species of Milnesium in the slenderness

and great length, relative to that of the

buccal tube, of the primary branches of

the claws on all legs. Primary branches of

the claws on the third and fourth legs are

especially long—the pt values of these

structures exceed those of M. longiungue

Fig. 1. Milnesium zsalakoae. Phase contrast images. A, Habitus. B, Buccopharyngeal apparatus and eye,

lateral view. Scale bars: A, 100 mm; B, 20 mm.

VOLUME 123, NUMBER 2 115

(mean pt claw III main branch 65.4, mean

pt claw IV main branch 87.5; Tumanov

2006), hitherto the species with the

longest reported main claw branches.

Milnesium zsalakoae differs from M.

reticulatum, M. katarzynae, and M.

krzysztofi in having a smooth cuticle.

Among species with smooth cuticles, it

differs from M. dujiangensis in having

main branches on all claws, from M.

tetralamellatum in having six peribuccal

lamellae, from M. eurystomum and M.

jacobi in having a substantially narrower

buccal tube, from M. antarcticum and M.

tardigradum in lacking accessory points

on the main claw branches, from M.

brachyungue in having much longer main

claw branches, from M. almatyense and

M. reductum in having basal spurs on the

secondary branches of the outer claws on

legs II to IV, and from M. asiaticum in

having a much shorter buccal tube and a

much larger pt index for the main branch

of leg IV. The Cretaceous species Milne-

sium swolenskyi closely resembles M.

tardigradum (Bertolani & Grimaldi 2000)

and can be differentiated from M. zsala-

koae in the same way as M. tardigradum.

In the most recent published key to

Milnesium (Tumanov 2006) the new

species keys out to the couplet occupied

by M. reductum and M. longiungue.

Fig. 2. Milnesium zsalakoae. Phase contrast images. A, Claw, leg II. B, Claw, leg III. C, Claw, leg IV.

Scale bars: 20 mm.


Milnesium zsalakoae brings the number

of tardigrade species reported from New

Mexico to 21 (Mehlen 1969, Beasley

1988) and from Arizona to 13 (Schuster

& Grigarick 1965, Beasley 1988). It is one

of the few Milnesium species recorded

from more than one location (Table 1).

Milnesium jacobi, new species

Figs. 3, 4; Table 2

Material examined.—Holotype: from

foliose and fruticose lichens on tree,

intersection of County Road 484 and

U.S. 84, Mexia, Limestone Co., Texas,

U.S.A. (31u409420N, 96u319010W; eleva-

tion 162 m), 3 Sep 2008, WAKSM slide

number 9352. Three paratypes, same

collection data as for holotype, WAKSM

slide numbers 9338 and 9352. Seven

additional specimens collected from same

site 7 Apr 2001.

Diagnosis.—Smooth cuticle. Main claw

branches long, slender, with well-devel-

oped accessory points. Short basal spurs

on inner claw branches. Very wide,

cylindrical buccal tube (mean pt 57.1).

Very posterior stylet support insertion

(mean pt 87.9).

Description of holotype.—Body length

669.3(Fig. 3A).Bodywhiteortransparent,

cuticle smooth. Eyes present. Buccal appa-

ratus with six peribuccal papillae, two

lateral papillae, and six peribuccal

lamellae (Fig. 3B). Buccal tube 38.3 long

and 21.2 [55.4] wide. Stylet supports

inserted on buccal tube at 32.9 [86.0]. Claws

of Milnesium type (Fig. 4A–C). Claw bases

+ secondary branches robust, with short

spurs.Mainclawbranches longandrobust,

with small accessory points. Internal claw

lengths: leg I main branch 17.9 [46.7], claw

base + secondary branch 12.8 [33.4], basal

spur 3.0 [8.2]; leg II mb 20.7 [56.4], cb + sb

15.4 [40.2], basal spur 3.2 [8.7]; leg III mb

19.5[53.1], cb+ sb14.3 [39.0],bs3.4 [9.3]; leg

IV mb 25.3 [69], cb + sb 16.0 [41.8], bs 5.0

[13.6]. Slender transverse cuticular bars.

Remarks.—Summary morphometric da-

ta and pt indices for the holotype, para-

types, and seven other specimens are given

in Table 2. Two of 11 specimens had eyes in

lateral position. No eggs were found.

Fig. 3. Milnesium jacobi. Phase contrast images. A, Habitus. B, Buccopharyngeal apparatus and eye,

ventral view. Scale bars: A, 100 mm; B, 20 mm.


Etymology.—The specific name honors

the second author’s brother, Jacob M.

Guillory, and her grandson, Jacob M.

Hinton.

Discussion and differential diagnosis.—

Milnesium jacobi differs from all other

Milnesium species in having a broad,

cylindrical buccal tube and exceptionally

posterior placement of the stylet support

insertions. Only M. eurystomum has a

wider buccal tube. The buccal tube in M.

eurystomum, however, narrows anterior

to posterior (width at the mouth exceeds

30), while the diameter of the buccal tube

in M. jacobi is the same throughout its

length (maximum diameter in any speci-

men 27.2). The new species differs from

M. dujiangensis in having main claw

branches. Unlike M. katarzynae, M.

krzysztofi, and M. reticulatum, M. jacobi

has a smooth cuticle without reticulation.

Accessory points are present on main

claw branches in M. jacobi but not in M.

reductum and M. longiungue. Milnesium

jacobi has much longer main claw branch-

es than M. brachyungue but much shorter

main claw branches than M. zsalakoae.

Milnesium almatyense and M. asiaticum

Fig. 4. Milnesium jacobi. Phase contrast images. A, Claws, leg I. B, Claws, leg III. C, Claws, leg IV. Scale

bars: 20 mm.


have longer basal spurs than M. jacobi.

Unlike M. antarcticum, the new species

has basal spurs on the fourth claw. Unlike

M. jacobi, M. tetralamellatum has four

peribuccal lamellae. Claws of M. tardi-

gradum are much shorter than those of

M. jacobi. The Cretaceous species Milne-

sium swolenskyi closely resembles M.

tardigradum (Bertolani & Grimaldi 2000)

and can be differentiated from M. zsala-

koae in the same way as M. tardigradum.

In the most recent published key to

Milnesium (Tumanov 2006) the new

species keys out to the couplet occupied

by M. asiaticum and M. almatyense.

Milnesium jacobi brings the number of

tardigrade species reported in Texas to 19

(Hinton & Meyer 2007).

Acknowledgments

We wish to thank Joan Rettke, who

helped with field collection in Arizona

and New Mexico. Mark Paulissen and

Tabatha Hibbs of Tahlequah, Oklahoma,

provided a safe haven to the first author

when he was compelled to evacuate from

Hurricane Gustav.

Literature Cited

Beasley, C. W. 1988. Altitudinal distribution of

Tardigrada of New Mexico with the descrip-

tion of a new species.—American Midland

Naturalist 120:436–440.

Bertolani, R., & D. Grimaldi. 2000. A new

eutardigrade (Tardigrada: Milnesiidae) in

amber from the Upper Cretaceous (Turonian)

of New Jersey. Pp. 103–110 in D. Grimaldi,

Table 2.—Morphometric data and pt values of selected structures of Milnesium jacobi mounted in Hoyer’s

medium and polyvinyl lactophenol. All lengths in mm. Range refers to the smallest and largest structure

found among all measured specimens.

Character n

Range Mean SD

Length pt Length pt Length pt

Body length 10 393.8–711.8 n.a. 554.2 n.a. 120.1 n.a.

Buccal tube length 10 32.1–44.1 n.a. 37.6 n.a. 3.1 n.a.

Stylet support insertion 8 26.7–37.5 83–93.3 32.9 87.7 3.3 4.4

Outer buccal tube width 10 15.3–27.2 41.4–70.7 21.4 57 3.3 8.3

Claw main branch length, Leg I 11 17–24.5 46.3–66.8 19.5 53.2 2.2 3.4

Basal claw + secondary branch

length, Leg I 10 12.1–16.4 33–37.7 13.8 36.9 1.2 3

Claw basal spur length, Leg I 4 3.0–6.0 7.8–17.1 4.7 12.5 1.3 3.8

bb, Leg 1 4 2.2–4.3 n.a. 3.1 n.a. 0.9 n.a.

Claw main branch length, Leg II 10 17.7–27.3 45.2–64.2 21.1 56.2 2.6 6.1


length, Leg II 10 12.4–37.6 35.1–45.8 14.6 39.7 1.6 4.2

Claw basal spur length, Leg II 4 3.2–5.5 8.4–15.1 4.6 12.7 1 3.2

bb, Leg II 4 2.5–4.8 n.a. 3.3 n.a. 1.1 n.a.

Claw main branch length, Leg III 10 19.3–26.4 50.9–72 22 59.5 2.5 7.6


length, Leg III 9 14.1–18.3 36.8–45.1 15 40 1.4 3.5

Claw basal spur length, Leg III 5 3.4–5.6 8.9–16 4.9 13.6 0.9 3.1

bb, Leg III 5 2.5–4.2 n.a. 3.1 n.a. 0.7 n.a.

Claw main branch length, Leg IV 11 21.9–33.7 68.1–82.6 26.9 73.1 3.3 9.0


length, Leg IV 9 13.4–21.4 34.4–51.8 16.9 44.9 2.7 5.9

Claw basal spur length, Leg IV 5 3.5–9.9 10.9–26.8 6.3 16.7 2.5 6.5

bb, Leg IV 5 1.5–4.6 n.a. 3.0 n.a. 1.3 n.a.

Abbreviations: n 5 number of specimens measured, SD 5 standard deviation, n.a. 5 not applicable,

pt 5 pt index.


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Associate Editor: Rick Hochberg.


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