9393

Porifera – Sponges Philippe Willenz et al.

Fig. 1

Fig. 2

94

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General Introduction

Sponges (or Porifera) are sedentary invertebrates,

which are generally restricted to marine environments,

except for a single suborder of freshwater demosponges

(Spongillina). They display the simplest stage of

metazoan organization; they possess a reduced number

of cell types and have no epithelium, organs, true

digestive, circulatory or nervous system. The body

wall of sponges is perforated by a multitude of pores

(ostia) opening into the aquiferous system (Fig. 1&2).

A network of inhalant canals leads to flagellated cells

(choanocytes) grouped in chambers, where particles the

size of bacteria are filtered and digested at the cellular

level through phagocytosis. Filtered water flows out

through exhalant canals. These open to the outside

through one or several large tubes visible to the naked

eye, the oscula (Fig. 1). The water flow brings in food and

oxygen and also removes waste.

Currently, at least 15,000 sponge species are estimated

to exist worldwide of which, only approximately 7,000

are properly described in the literature. This number

is increasing due to both SCUBA-diving explorations

in poorly known regions and the taxonomic study of

material that has been gathered through oceanographic

inventories and deposited in collections around the

world. The Phylum Porifera is subdivided into three

classes (Hexactinellida, Calcarea and Demospongiae),

mainly according to the composition and structure of

their skeletal elements.

Sponges that are assigned to the Hexactinellida possess a

skeleton of six-rayed siliceous spicules. They occur mainly

in deep marine waters. So far, there are no records of this

class in the Chilean Fjord Region; although they may be

a dominant component of the Antarctic

benthos and in North East Pacific fjords.

Calcarea have a skeleton comprised of

spicules of calcium carbonate, which

are mostly three-rayed. Demospongiae

are by far the most abundant class of

Porifera. They represent 85–90% of the

global sponge fauna and include all of

the relatively few freshwater species.

Almost all Demospongiae possess a

skeleton of siliceous spicules, sometimes

supplemented or entirely replaced by

an organic collagenous skeleton. A few

species completely lack a skeleton.

Porifera – Sponges Philippe Willenz et al.

95

Class Calcarea

Philippe Willenz, Fernanda Azevedo, Eduardo Hajdu, Michelle Klautau

wide distribution from tropical to polar regions and from

shallow waters to the deep sea.

Two subclasses are recognized in the class Calcarea:

Calcinea and Calcaronea, with five orders, 22 families

and 75 valid genera.

Collecting calcareous sponges is not easy as they are

frequently small and inconspicuous and live in cryptic

habitats. The calcareous sponges of the Chilean coast are

poorly known. The few species described recently by the

authors are the first ones for the entire fjord region.

Class Demospongiae

Philippe Willenz, Eduardo Hajdu, Ruth Desqueyroux-Faundez, Gisele Lôbo-Hajdu, Mariana de Souza Carvalho

MorphologyDemosponges vary greatly in size. In the Chilean Fjord

Region they vary from a few millimetres to up to half a

meter in height. The body forms of Demosponges are

usually irregular and exhibit massive, encrusting, erect

or branching patterns. The type of growth pattern is

influenced by the nature of the substratum, the velocity

of the water currents and the wave action. The same

species can have different shapes under different

environmental conditions, sometimes resulting in

taxonomic confusion. Another possible source of

sponge misidentification is that they may be confused

with colonial tunicates, which have a porous surface

similar to that of sponges.

Growth occurs at terminal points in arborescent forms,

along growing fronts in encrusting species and all over

the surface in massive forms. There is no definitive

maximum size as growth is usually indeterminate. The

same species may be represented by individuals of

variable sizes and the larger ones are not necessarily

the eldest.

ReproductionAll sponges are capable of sexual reproduction and

some have several additional types of asexual processes.

Sexual processes are multiple. Sponges lack distinct

gonads and gametes and most of them are sequential

hermaphroditic; eggs and sperm are produced at different

times. In a single individual, the sex change may occur

Calcareous sponges represent approximately 9.5% of all

known sponges, with over 650 recognized species. The

calcium carbonate skeleton of extant calcareous sponges

is composed of three main types of spicules: diactines,

triactines and tetractines (spicules with two, three and

four tips). In some calcareans, a solid basal calcitic

skeleton can also be present. Calcarea is the only class

of Porifera that shows the three basic types of aquiferous

systems: asconoid, syconoid and leuconoid. Their mode

of sexual reproduction is exclusively viviparous, with

blastula larvae. They are exclusively marine and have a

only once or it may repeatedly alternate between male

and female. Some specimens however, are permanently

male or female. Cross-fertilization takes place in all cases.

Sperm usually originate from choanocyte chambers

that transform into spermatic follicles in which clusters

of flagellated cells undergo spermatogenesis. Oocytes

arise either from choanocytes or from archaeocytes and

develop surrounded by follicle cells and nurse cells. In

some demosponges the embryo may be released shortly

after fertilization or a long development may take place

inside the parent sponge (viviparity). Other demosponges

release eggs before fertilization (oviparity) and a larval

stage ensues inside a mucus envelope that adheres to the

substratum.

Asexual processes are also multiple. All sponges are

capable of regenerating new individuals from fragments

after mechanical damage. Reduction bodies called

gemmules are produced by freshwater sponges and

some rare marine sponges. Gemmules are small spheres

made of a hard shell of spongin that may be reinforced

with spicules. They are packed with cells that contain

food reserves and are highly resistant to freezing,

desiccation and anoxia for long periods of time. When

environmental conditions improve, gemmules hatch and

give rise to young sponges. Many marine sponges also

produce buds that form new individuals when they settle

on the substratum after falling from the parent sponge

surface.

More than any other marine invertebrate, sponges

99

Clathrina fjordica Azevedo et al., 2009

Common name: Lattice sponge (of the fjords);

Esponja rejilla (de los fiordos)

Description: Fragile and small (60x45x7 mm). Body

a mesh of irregular and loosely anastomosed tubes.

Aquiferous system asconoid. Colour in life white;

in ethanol light brown or beige. Skeleton: Without

organisation and composed of 2 categories of triactines.

Spicules: Triactines-1 equiangular and equiradiate; length

92–116 µm; thickness 8.3 µm; actines cylindrical, rounded

and undulated. Triactines-2 equiangular and equiradiate;

length 76–122 µm; thickness 9.9 µm; actines conical,

rounded and undulated. Possibility for confusion: C.

coriacea, which has only 1 category of triactines. The

other clathrinas cited for Chile are C. primordialis and

C. antofagastis. Both C. primordialis and C. fjordica have

2 categories of triactines: one cylindrical and the other

conical and a loosely anastomosed cormus, but the tips

of the actines are sharp in C. primordialis and rounded in

C. fjordica. C. antofagastis has 3 categories of triactines

with blunt tips.

Habitat: Hard substrates, also attached to mollusc

shells (Crepidula sp., Mytilus chilensis). Depth: 9–27 m.

Abundance: Common. Distribution: SE Pacific (NPZ–

CPZ). Chile: 42°S–48°S. Biology: Unknown. Comments:

When removed from the water, the tubes of the sponge

lose water, change shape and sometimes change colour.

Scale bars: Top, 2 cm; centre left and right, 2 cm; bottom

left and right, 100 µm.

Main reference: Azevedo et al. (2009).

A B

C

D

E F

Crambe chilensis

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Crambe chilensis Esteves et al., 2007

Common name: Orange barnacle crust sponge;

Esponja cubre-pico-roco naranja

Description: Small; encrusting. Oscula small;

inconspicuous; in centre of a starry arrangement of

clearly visible sub-superficial exhalant canals. Surface

smooth to slightly velvety. Consistency soft, slightly

flexible. Colour in life rosy-orange; in ethanol beige

or brown. Skeleton: Ectosomal skeleton composed of

brushes of subtylostyles, arranged perpendicularly or

tangentially to surface, isochelae concentrated adjacent

to surface. Acanthomicrorhabds commonly distributed

amongst isochelae and subtylostyles. Surface pierced

by megascleres of both ectosomal and choanosomal

skeletons. Choanosomal skeleton composed of

tylostyles erect on substrate, tyles embedded in layer

of interconnected astroclone desmas lying adjacent

to substrate. Choanosome with isochelae (rare) and

acanthomicrorhabds (common). Spicules: Megascleres:

principal tylostyles mostly smooth, straight or slightly

curved, apices sharp or mucronated, bases smooth or

slightly tuberculated, length 245–833 µm, thickness

13–46 µm (A); auxiliary subtylostyles, sometimes styles,

apices with or without microspines (visible only with

SEM), length 186–387 µm, thickness 4–14 µm (B,C);

astroclone desmas, usually with 5–6 rays, simple or

bifurcated, Ø 50–232 µm (E). Microscleres: anchorate

isochelae with 5–7 teeth on each side, length 21–37

µm (F); acanthomicrorhabds slightly fusiform, straight or

abruptly bent, with spines in spirals around shaft, 30–67

µm (D); raphides straight or slightly curved, observed in

only 1 specimen, 175–240 µm (not illustrated). Possibility

for confusion: Other Crambe species which do not have

the spicule assemblage of Crambe chilensis: principal

tylostyles, astroclone desmas, anchorate isochelae

and acanthomicrorhabds. Another rosy-orange crust,

Hymedesmia sp., has slightly elevated, irregular, surface

pore fields, which look like scars.

Habitat: Steep rock walls. All collected specimens were

growing over barnacles (Arossia henryae). Depth: 12–21

m. Abundance: Infrequent. Distribution: SE Pacific

(NPZ). Chile: 42°S–43°S. Biology: Associated with the

barnacle Arossia henryae. Scale bars: Top left and right,

2 cm; A, 100 µm; B, 50 µm; C, 5 µm; D, 10 µm; E, 50

µm; F, 5 µm.

Main reference: Esteves et al. (2007).

Crellomima tenuissima (Thiele, 1905)

Common name: Translucent yellow crust sponge;

Esponja costra amarilla-translucida

Description: Thinly encrusting. Oscula not visible.

Subdermal canals only slightly visible. Surface smooth.

Consistency soft. Colour in life dull light yellow; in

ethanol whitish. Skeleton: Ectosomal skeleton composed

of a tight, interwoven, tangential arrangement of

acanthoxeas and of common, scattered microscleres.

Choanosome hymedesmioid, acanthostyles erect on

substrate. Spicules: Megascleres: acanthoxeas slightly

spined, slightly fusiform, sharply terminated, length 170–

190 µm, thickness 5 µm (A–C); acanthostyles slightly

curved, length 220–340 µm, thickness 12–15 µm, with

sharp apex (D). Microscleres: anchorate isochelae,

polydentate, in 2 categories: large, rare, with regular,

roundish alae, length 21–30 µm (E); small, common,

with sharp, irregularly outlined alae, length 10–14 µm

(F–I). Possibility for confusion: Other yellow encrusting

species: Clathria rosetafiordica, Hymenancora sp. and

Clathria mytilifila. An identification key for these species

is provided following the species list.

Habitat: Steep rocky substrates or underneath relatively

small boulders. Depth: 10–21 m. Abundance: Rare.

Distribution: SE Pacific (NPZ). Chile: 42°S–44°S.

Biology: Unknown. Scale bars: Top, 5 cm; centre left,

2 cm; A, D, 50 µm; B, C, 5 µm; E–I, 10 µm.

Main reference: Desqueyroux (1976).

159

Glossary

This section indicates the terms and the information that should be recorded when collecting a sponge specimen. It

is also intended as a reference for the definition of terms found in the sponges descriptions of this guide. Terms are

arranged in alphabetical order (After Boury-Esnault and Rützler, 1997).

Acantho-

sphaerostrongylaster

Sphaerostrongylaster with spines.

Acanthostrongylaster Strongylaster with spines.

Acanthostyle Spined style (e.g. Clathria, Iophon).

Actine Centred ray of a spicule containing an axis or axial canal. See clad.

Ala (pl. alae) One of the thin, wing-like or spatulate structures in each curved portion of a chela. The anterior ala

is the one facing the shaft; the others are lateral alae. See chela.

Amphiblastula Hollow, ovoid larva, with anterior flagellated and posterior

nonflagellated groups of cells; typical of Calcaronea (Calcarea).

Anastomosed tubes Interconnected asconoid tubes (e.g. Clathrina) (Calcarea).

Anastomosing skeleton Tracts, lines, or fibres are interconnected. (= Reticulate).

Anatriaene

A triaene in which the clads are sharply curved

backward (e.g. Stelletta).

Anchorate chela

An isochela with 3 or more free alae (at each

end) in the form of recurved processes shaped

like anchor claws or anchor blades, with 2

incipient lateral alae fused with the shaft over

their entire length and a gently curved, not

abruptly arched shaft (e.g. Clathria, Crambe).

Anisochela

A chela with unequal ends (e.g. Clathria

rosetafiordica, Iophon proximum, Mycale).

Anisotropic skeleton

Reticulate skeleton with primary and secondary

tracts, lines, or fibres (e.g. Haliclona).

Apical actine The 4th actine of a tetractine, which is joined to the basal triradiate system (Calcarea).