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

as far north as the Beaufort Sea (de Laubenfels, 1953).
Sponges inhabit a broad depth range and occur from
the intertidal zone to the deep-ocean trenches. About
24% (30 of 125 species) of the sponges known from the
Aleutian Islands appear to be endemic to the region.
Deep-water sponges, like deep-water corals, are exceptionally
abundant and diverse in the Aleutian
Islands (Stone, 2006) and not surprisingly, since both
faunal groups have similar habitat requirements. Both
groups require stable water currents for feeding and
other metabolic processes and most require hard,
exposed substrate for attachment. The geology and
oceanography of the Aleutian Island Archipelago provide
unique conditions to fulfill both requirements.
The Archipelago contains more than 300 islands and
extends over 1900 km from the Alaska Peninsula to the
Kamchatka Peninsula in Russia. The Archipelago is supported
by the Aleutian Ridge that forms a semi-porous
boundary between the deep North Pacific Ocean to the
south and the shallower Bering Sea in the north. The
Aleutian Ridge is a volcanic arc, with more than 20 active
volcanoes and frequent earthquake activity that was
formed along zones of convergence between the North
American Plate and other oceanic plates (Vallier et al.,
1994). The island arc shelf is very narrow in the Aleutian
Islands and drops precipitously on the Pacific side to
depths greater than 6000 m in some areas, such as the
Aleutian Trench. Deep water flowing northward in the
Pacific Ocean encounters the Aleutian Trench where it
is forced up onto the Aleutian Ridge and into the Bering
Sea through the many island passes (Johnson, 2003).
Additionally, coastal water from the Alaska Stream enters
through Unimak Pass in the eastern Aleutians and
slowly flows northeastward along the Alaska Peninsula.
The Aleutian North Slope Current flows eastward on
the north side of the Aleutian Islands towards the inner
continental shelf of the Bering Sea. This is a swift current
and the steep continental slope forces much of the
flow into the northwest-flowing Bering Slope Current
(Johnson, 2003).
The collections made by Lambe (1900), de Laubenfels
(1953), and Koltun (1958, 1959) provide a firm
basis to closely examine the zoography of sponges from
the region. The sponge fauna of the Aleutian Island
Archipelago has strong taxonomic affinities with the
sponge fauna of the Sea of Okhotsk (30% of species in
common), seas of the Arctic Ocean (22% of species in
common), the eastern (18% of species in common) and
western Bering Sea (10% of species in common), and
the Sea of Japan (17% of species in common). By comparison,
only 12% of the sponge fauna from the Gulf of
Alaska is common with that of the Aleutian Islands. This
zoogeographic pattern has undoubtedly been influenced
to some degree by historical sampling effort, but
the taxonomic affinities of the Aleutian Island sponge
fauna are clearly much greater with the sponge fauna
to the west and north than they are with the eastern
fauna. Burton (1934) suggested that earlier work by
both Lambe and de Laubenfels indicated that the Arctic
influence was apparent as far south as Vancouver Island.
Several species are known from areas immediately adjacent
to the Aleutian Island Archipelago and, although
not yet reported from the region, likely occur there
based on geographical proximity. These include species
from the eastern Bering Sea (e.g., Aaptos kanuux) and
the Commander Islands (Russia) in the western Bering
Sea (e.g., Grantia monstruosa, Polymastia laganoides,
Asbestopluma gracilis, and Axinella hispida).
Biology of sponges
Basic diagrams of sponge morphology, spicule types
and skeletal structures, and a comprehensive glossary of
terminology are available in the Thesaurus of Sponge
Morphology by Boury-Esnault and Rützler (1997) and
can be accessed via the World Porifera Database (Van
Soest et al., 2008). 2
Sponges are a primitive group of metazoans. They are
sedentary animals, but a few species (e.g., Craniella spp.)
may be free-living (unattached) during part of their life
cycle (Lehnert and Stone, 2011). The dominant feature
of the typical sponge body plan is the aquiferous system
through which massive amounts of water are pumped
(e.g., some large sponges are capable of filtering their
own volume of water every 20 seconds). Water flow is
unidirectional and maintained by flagellated cells (choanocytes)
that are usually contained within chambers
where oxygen and food particles are taken up by various
cell types. Water flows in through inhalent pores or ostia
and out through one or more larger exhalent openings
or oscula. The oscula may open into a large cavity called
an atrium or spongocoel (i.e., the large opening in tube-
or vase-shaped sponges).
The sponge body consists of two distinct regions:
the outer region (ectosome) and the central or inner
region (choanosome) where the choanocyte chambers
are located. Each region typically has distinct skeletal
structures with a diagnostic complement of spicules.
Spicules are grouped into two main categories: megascleres
and microscleres. Megascleres are typically larger
and provide the primary skeletal support. Microscleres
are smaller (i.e., a microscope is required to see them)
and generally function as packing and reinforcing
2 The database can be found online at http://www.marinespecies.
org/porifera/. Click on “Sources”; type “Boury-Esnault” in “Sourcename”;
type “publication” in “Sourcetype”; check the box to
“Limit to sources with full text”; and click on “Search” in lower right
corner.
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