A guide to the deep-water sponges of - NMFS Scientific Publications ...

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structures. Many sponge cells are highly mobile and can
move freely within the extracellular matrix. Some cells
are also extremely pluripotent (i.e., capable of differentiating
into other cell types) and sponges are capable
of easily remodeling cell-cell junctions. These features
probably allow sponges to adapt to diverse and extreme
habitats and are largely responsible for the extreme phenotypic
plasticity displayed by some sponges that makes
identification from photographs alone so problematic.
Sponges are generally nonselective filter feeders,
feeding principally on bacteria, fungi, diatoms, dinoflagellates,
and detritus (Bergquist, 1978; Pile et al.,
1996). A recent study, however, has shown that some
hexactinellid species do exhibit size independent selective
filtration of ultraplankton (Yahel et al., 2006).
Carnivorous sponges were recently discovered that lack
an aquiferous system altogether and possess structures
modified to ensnare and capture larger prey such as
zooplankton (Vacelet and Boury-Esnault, 1995; Watling,
2007). Carnivorous species in Alaska are deep-water inhabitants
and include Cladorhiza corona (Lehnert et al.,
2005), Cladorhiza bathycrinoides, Chondrocladia concrescens,
and possibly Abestopluma ramosa.
Few studies have been conducted on the growth rate
and longevity of sponges, particularly those found in
deep-water habitats and high-latitude ecosystems. No
studies have been conducted on the growth of sponges
in Alaska. In general, the growth rate of temperatewater
sponges appears to be seasonal and relatively
slow, occurring at rates comparable to those of deepwater
corals (Ayling, 1983; Thomassen and Riisgård,
1995; Fallon et al., 2010). Studies on the hexactinellid
sponge Acanthascus (Rhabdocalyptus) dawsoni in British
Columbia indicate a growth rate of 1.98 cm/yr and a life
span of more than 200 years (Leys and Lauzon, 1998).
Studies on the hexactinellid sponge Aphrocallistes vastus
in British Columbia indicate that it may grow considerably
faster (10 cm/yr) but still live in excess of a century
(Austin et al., 2007). We hypothesize that growth rates
for sponges in Alaska are similar to those for British
Columbia sponges but note that growth studies, particularly
on demosponges, should be a high research priority
in Alaska so that recovery rates from disturbance for
sponge habitats can be estimated.
Deep-water sponges in the Aleutian Islands appear
to have few predators. We have observed blood stars
(Henricia spp.) displaying a typical feeding posture on
several demosponges (e.g., Artemisina sp., Monanchora
pulchra, Semisuberites cribrosa, and Haliclona sp.) at shallower
depths (80 to 300 m). An earlier interpretation
of this behavior, however, was that the sea stars were
simply taking advantage of the sponges’ feeding currents
(Anderson, 1960). Henricia were generally accepted
as suspension feeders (Anderson, 1960), but
our additional observation of large numbers of these
sea stars present on dead sponges and decaying sponge
fragments in debris “windrows” further implicate predation
(or scavenging). In deeper water Hippasteria spp.
sea stars appear to prey on several species of sponges. In
the eastern Gulf of Alaska several sea stars (Hippasteria
spp., Henricia longispina, and Poraniopsis inflata) prey on
glass sponges (including Acanthascus dawsoni dawsoni,
A. solidus, Aphrocallistes vastus, and Heterchone calyx) and
several sea stars (Hippasteria spp., H. longispina, P. inflata,
Pteraster tesselatus, and Ceramaster patagonicus) prey
on demosponges (including Poecillastra tenuilaminaris,
Halichondria sp., and Mycale loveni). The incidence of
predation on deep-water sponges in Alaska, however,
appears to be relatively low and limited to only a few
species of sea stars.
Advances are now being made in the study of the
reproductive biology of sponges, but our current
knowledge is based on studies of a small fraction of the
species described to date worldwide; none from Alaska
(Maldonado and Berquist, 2002). Sponges display
highly diverse mechanisms of embryogenesis, larval
differentiation, and reproduction that include both
sexual and asexual processes (Berquist, 1978; Leys and
Ereskovsky, 2006; Ereskovsky, 2010). Sexes are either
temporarily or permanently separate and some species
are hermaphroditic (Blake and Lissner, 1994). Many
species are capable of regenerating viable adults from
fragments, and additional asexual processes include
the formation of gemmules and reduction bodies,
budding, and possibly formation of asexual larvae
(Maldonado and Berquist, 2002). Some species are
oviparous while others are viviparous and brood larvae.
Release of propagules (gametes, zygotes, or early embryos)
is highly synchronous in oviparous species, but
asynchronous in viviparous species that release fully
brooded flagellated larvae (Maldonado and Berquist,
2002). Several species of Geodiidae are gonochoristic
and oviparous and this is assumed to be the general
condition for the family (Cárdenas et al., 2009). Some
species are viviparous, such as Stylocordyla, which has the
added peculiarity that larvae are retained alive in the
body until they have fully developed (Bergquist, 1972).
Gemmules, reproductive structures that can survive
adverse conditions such as desiccation or extreme cold,
are not typically produced by marine sponges. Their
common occurrence in hermit crab sponges may represent
an adaptation to help counter the consequences
of stranding on shore.
Many sessile marine fauna, including sponges, have
evolved the ability to produce or accumulate from associated
microorganisms a diversity of unique chemical
compounds or secondary metabolites that they utilize
in predator defense, competition for resources, and
as physiological adaptations to living in extreme environments
(Haefner, 2003). More than 12,000 novel