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