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

101. Halichondria (Eumastia) sitiens (Schmidt, 1870)
Description. This sponge has a short stalk that typically
branches into several agglutinated tubes. Consistency
is inelastic and stiff due to a combination of high
spicule density and lack of spongin, but easy to tear.
Oscula are not obvious. Height is to at least 15 cm. Color
in life is light brown, golden brown, or creamy white.
Skeletal structure. Spicules are arranged tangentially
in the ectosome as is typical for the genus. The choanosome
is constructed by polyspicular tracts and many
spicules without orientation in between. Oxeas are of
a wide size range (145–1200 × 5–20 µm).
Zoogeographic distribution. Cosmopolitan and locally
common. In Alaska – central Aleutian Islands,
Bering Sea (Pribilof Canyon), and Arctic Ocean. Elsewhere
– North Pacific Ocean, Arctic Ocean, and North
Atlantic Ocean.
Habitat. In Alaska – attached to boulders and cobbles
at depths between 97 and 167 m (central Aleutian
Islands). In the Bering Sea it attaches to cobbles and
pebbles at depths between 208 and 300 m. Elsewhere –
reported at depths between 6 and 220 m.
Remarks. Koltun (1959) described a cushion-shaped
sponge with a surface of numerous elongated papillae
with oscula on top. The agglutinated small tubes of the
Aleutian Island specimens are the equivalent of these
papillae in a fully grown sponge. The very long oxeas
in halichondroid confused arrangement occur in both
specimens and are regarded as diagnostic.
Photos. 1) Specimen collected at a depth of 167 m
in the central Aleutian Islands. Grid marks are 1 cm 2 .
2) Same specimen as in photo 1 (center) in situ growing
in a cluster of the same species. 3) Fragmented specimen
collected at a depth of 300 m in Pribilof Canyon,
Bering Sea.
121