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

5. Farrea occa occa Bowerbank, 1862
Description. Lace-like hemispheric mass has largecaliber
(1.5 to 2-cm diameter), short, branching and
anastomosing tubes increasing in size (of the mass)
by lateral growth, attached to hard substrate at central
origin and at multiple lateral contact sites. Surface of
the mass is labyrinthic with open ends of tubes functioning
as oscula, but external and internal surfaces
of individual tube elements are smooth. Consistency is
flexible but brittle and fragile due to breakage of the
very thin fused primary skeleton. An individual mass
from a single settled larva may reach 3 m in diameter
and over 1 m in height. Color in life is translucent white
to pale yellow.
Skeletal structure. SEM images of spicules are shown
in Appendix IV. The primary framework is a fused farreoid
lattice of hexactins forming a network of square
meshes with sides 79–494 µm long; it is continuous
throughout the specimen. Loose megascleres include
dermal and atrial pentactins (190–305 µm tangential ray
length, 78–280 µm proximal ray length); pileate and anchorate
clavules usually with smooth shafts, rarely with
one or two large spines (196–308 µm length); moderatesized
uncinates (0.89–2.64 mm length). Microscleres
are mainly oxyhexasters with relatively long primary
rays (57–111 µm in diameter). There may be a very few
discohexasters or onychohexasters.
Zoogeographic distribution. Locally common and
abundant in some areas. In Alaska – eastern Gulf of
Alaska. Elsewhere – cosmopolitan, but the previous
known northern limit of the subspecies was 55.4°N in
northern British Columbia; the new Alaska collections
extend the northern limit to 58.2°N.
Habitat. In Alaska – attached to bedrock, boulder, and
cobbles at depths between 91 and 238 m. Elsewhere
– attached to cobbles, bedrock, shell, coral skeletons,
and hexactinellid sponge skeletons at depths between
86 and 1360 m.
Remarks. This may be the largest species of sponge in
the North Pacific Ocean, with a diameter reaching 3 m.
This sponge provides much refuge habitat for small fish
and micro-invertebrates that may be forage species for
larger fish and crabs.
Photos. 1) Fragment of a specimen collected at a
depth of 168 m in the eastern Gulf of Alaska. Grid marks
are 1 cm 2 . 2) Specimen at a depth of 165 m in the eastern
Gulf of Alaska.
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