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

46 Professional Paper NMFS 12
30. Poecillastra tenuilaminaris (Sollas, 1886)
Description. This sponge is polymorphic but typically
has a plate-like or lamellar growth form. The surface of
the sponge is smooth to the unaided eye but microscopically
hispid. Small oscula occur on one side only. The
consistency is firm, incompressible, and fragile. Size is
highly variable but attains a length and height exceeding
more than 1 m. Color in life is whitish to light brown,
often with a dark fringe at the distal edge.
Skeletal structure. The choanosome consists of an
unorganized mix of calthrops and oxeas: calthrops
(320–540 × 35–48 µm per ray), occasionally triods with
rays of the same size, oxeas (1240–2650 × 32–47 µm).
Microscleres are streptasters (14–28 µm) and acanthose
microxeas (117–157 × 3–5 µm) that are always bent in
the middle.
Zoogeographic distribution. Common. In Alaska –
Bering Sea (Zhemchug Canyon) and eastern Gulf of
Alaska. May reach densities up to 19 per m 2 in eastern
Gulf of Alaska habitats. Elsewhere – holotype described
from Sea of Japan, also reported from along the California
Coast and the Gulf of California. Present records
strongly suggest a circumboreal distribution in the
North Pacific. However, morphological differences do
exist between populations, suggesting some genetic
isolation (see Remarks).
Habitat. In Alaska – attached to bedrock at depths
between 149 and 486 m in the Bering Sea and attached
to bedrock, boulders, and cobbles at depths between
71 and 255 m in the eastern Gulf of Alaska. Elsewhere
– reported at depths to 74 m.
Remarks. Previously known as Normania tenuilaminaris
Sollas 1886, P. tenuilaminaris was originally described as
having straight acanthose microxeas. The microxeas we
examined from the Bering Sea specimens were consistently
bent but this is the only difference between the
specimens and in our opinion not sufficient to separate
the specimens at the species level. However, it is probable
that the Bering Sea population is genetically isolated
and may have developed different morphological
characters, such as the bent microxeas. This species is
preyed upon by the sea stars Hippasteria spp., Poraniopsis
inflata, Pteraster tesselatus, Ceramaster patagonicus, and
possibly Henricia longispina. We have observed a very
similar sponge in the central Aleutian Islands at depths
between 142 and 1386 m but we would need to collect
a specimen to confirm conspecificity.
Photos. 1) Fragments of specimen collected at a depth
of 175 m in the eastern Gulf of Alaska. Note the hydroids
growing on the fringe. Grid marks are 1 cm 2 . 2) Same
specimen as in photo 1 in situ. 3) Specimen collected
at a depth of 486 m in Zhemchug Canyon, Bering Sea.
Grid marks are 1 cm 2 .