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

25. Craniella sigmoancoratum (Koltun, 1966)
Description. Body is globular with very long tracts
of protruding spicules. Typically is attached to other
sponges via these tracts which terminate in anchorlike,
long-shafted triaenes. Internal bundles of spicules
radiate from the center of the globular body to well
beyond the surface of the sponge. The surface consists
of a layer of dermal oxeas occurring only there and
oriented perpendicular to the surface. The diameter
of the body is 7 to 8 mm (without protruding spicules).
Spicule tracts protrude 6–8 mm above the surface, giving
the sponge a spiny appearance. Color in life is white
or creamy white.
Skeletal structure. Large oxeas have unequal ends
(3000–8000 × 45–72 µm), cortical oxeas (460–1340
× 26–76 µm), protriaenes (1600–7300 µm long with
clads 13–34 µm), anatriaenes have rhabds (2300–8700
µm with clads 19–40 µm). The sigmaspires are unique
among the known species of Craniella in that they are
relatively large and resemble isochelae (22–34 µm).
These sigmaspires are abundant and densely present in
the cortical layer.
Zoogeographic distribution. Uncommon. In Alaska –
central Aleutian Islands, Bering Sea (Pribilof Canyon).
Elsewhere – previously known only from the original
description in the Kuril Islands, Russia.
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Habitat. In Alaska – a cryptic species; epizoic on
hexactinellid sponges and other demosponges, including
Erylus aleuticus, at depths between 190 and 275 m.
Elsewhere – no information available.
Remarks. Previously known as Tetilla sigmoancoratum
Koltun, 1966, but recently transferred to the genus
Craniella since it possesses both a cortex and the special
cortical oxeas that are lacking in the genus Tetilla.
Photo. 1) Specimen collected at a depth of 208 m in
Pribilof Canyon, Bering Sea. Specimen is growing on
an unidentified hexactinellid sponge.