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

20 Professional Paper NMFS 12
8. Tretodictyum sp. nov. Reiswig and Stone, in preparation
Description. This sponge has a thin-walled flaring
funnel or trumpet that attaches to hard substrate by
a short narrow stalk ending in a small basal disc. The
outer dermal surface is smooth with a thin transparent
spicule lattice covering a system of radiating ridges (average
1.1 mm wide) and grooves (average 0.8 mm wide)
visible to the naked eye. The internal atrial surface, also
smooth, is thoroughly and evenly pocked by openings
of small exhalant canals (average 1.5 mm diameter).
Under low magnification all surfaces appear furry due
to projecting ends of uncinate and scopule spicules.
Consistency is stony hard but crumbly and quite brittle.
Only a single partial specimen was collected and measured
25.4 cm tall by 20.6 cm wide at the margin; wall
thickness was 5–6 mm. Color in life is white; specimens
dried or preserved in ethanol are brownish orange.
Skeletal structure. The main skeleton is a rigid framework
of fused hexactins with grooves and septa typical of
the genus. Loose megascleres include rough pentactins
to hexactins with short distal ray (19–164 µm long), tapered
tangential rays (106–473 µm long), and proximal
rays (94–896 µm long); small rough regular hexactins
(84–177 µm long rays); scopules with rounded tine tips
(294–965 µm total length); uncinates (437–1480 µm
long). Microscleres are mostly oxyhexasters and hemioxyhexasters
(93%) with 1–4 nearly smooth, robust terminal
rays (53–73 µm diameter); stellate discohexasters
(7%) with 4–10 finely rough terminal rays (50–75 µm
diameter); a very few oxyhexactins (>1%) similar in size
to oxyhexasters.
Zoogeographic distribution. Locally abundant. In
Alaska – central Aleutian Islands. Elsewhere – not
reported.
Habitat. Occurs singly on bedrock, mudstone, boulders,
and cobbles at depths between 704 and 1264 m.
Photos. 1) Preserved (frozen) specimen collected at
a depth of 866 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.