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

11. Regadrella okinoseana Ijima, 1896
Description. This tube or sac sponge attaches basally
to hard substrate. Lateral walls bear distinctive smooth
depressions, each with a small (1–3 mm diameter) central
hole (parietal osculum) connecting to the atrial cavity;
edges around depressions often project several millimeters
as parietal ledges; the large terminal osculum
is normally covered by a coarse sieve plate and bordered
by a flaring marginal cuff. Consistency is slightly compressible
and rubbery. The partially collected Alaskan
specimen lacked an oscular sieve plate, marginal cuff,
and parietal ledges. Its atrial cavity was subdivided by
longitudinal wall fusions. It is estimated to have been 25
cm long by 13 cm diameter, but elsewhere incomplete
specimens 48 cm long have been reported. Color in life
is white; drab when dried or preserved in ethanol.
Skeletal structure. While the Aleutian specimen may
have unusual morphology, its spiculation is typical for
the species. Its skeleton consists mainly of loose spicules;
spicule fusion is present only in the lower parts collected
and is assumed to have been extensive in the basal part
left on the attachment site. Megascleres include thick
principal diactins with rounded tips (5–16 mm long);
thin diactins with pointed tips (1.3–7.5 mm long);
sword-shaped dermal hexactins with short, tapered,
pointed distal rays (89–369 µm length), tapered and
pointed tangential rays (156–318 µm length), and long
tapered proximal rays (232–807 µm length); regular
hexactins (134–292 µm ray length); atrial pentactins
with sharp tapered tangential rays (122–295 µm ray
length) and longer proximal rays (137–563 µm ray
length); a few atrial triactins and stauractins of similar
shape and size; short, thick atrial diactins (347–1047 µm
length); small diactins around parietal oscula (42–197
µm length). Microscleres include mainly oxystaurasters
(61–107 µm diameter); a few oxyhexasters (70–129 µm
diameter); dermal floricomes (78–113 µm diameter)
with 10–14 terminal rays ending in heads with 2–3 teeth;
remnants of graphiocomes are common, with central
(25–43 µm diameter) and terminal rays as dispersed
thin raphides (141–237 µm long).
Zoogeographic distribution. Widespread but uncommon.
In Alaska – central Aleutian Islands. Elsewhere
– reported from Indo-West Pacific Region including
from near India, Northwest and South Australia, New
Zealand, New Caledonia, Indonesia, Japan.
25
Habitat. In Alaska – occurs singly on mudstone, bedrock,
and possibly hexactinellid skeletons at depths between
1071 and 1395 m. Elsewhere – reported at depths
between 390 and 1264 m.
Remarks. The new record of this species in the Aleutian
Islands represents a range extension of over 3700
km from the nearest previous known site near Japan.
Photos. 1) Fragment of preserved (frozen) specimen
collected at a depth of 1386 m in the central Aleutian
Islands. Grid marks are 1 cm 2 . 2) Same specimen as in
photo 1 in situ. The separation between the red laser
marks is 10 cm.