porifera – sponges
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Porifera Sponges Philippe Willenz et al.
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 8590% 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.
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.
Philippe Willenz, Eduardo Hajdu, Ruth Desqueyroux-Faundez, Gisele Lbo-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
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
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
More than any other marine invertebrate, sponges
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
92116 m; thickness 8.3 m; actines cylindrical, rounded
and undulated. Triactines-2 equiangular and equiradiate;
length 76122 m; thickness 9.9 m; 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: 927 m.
Abundance: Common. Distribution: SE Pacific (NPZ
CPZ). Chile: 42S48S. 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 m.
Main reference: Azevedo et al. (2009).
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, isochel