Forcepia forcipis

(Bowerbank, 1866)

Species Overview

Forcepia forcipis (Bowerbank, 1866) a massive or thickly flabellate deep-water sponge. It has a punctate surface and a crumbly consistency. Its major feature are very long forceps microscleres (microscopic examination). It is a boreo-arctic North Atlantic sponge reaching the west coast of Ireland and the Swedish west coast as its southern limits.

Taxonomic Description

Colour: Greyish in alcohol, bright grey or brownish in dried state.
Shape, size, surface and consistency: Thickly massive or thickly fan-shaped; size 11 cm in widest expansion. Surface grooved, punctate, but mostly smooth, due to a thin detachable membrane. Numerous scattered oscules, up to 2 cm in diameter. Consistency rather firm, crumbly, not very elastic.
Spicules: (Forcepia forcipis spics) Megascleres : Ectosomal tylotes, barely swollen ends: 238-309 x 25 µm; choanosomal styles, smooth, slightly curved, rather short-spointed: 488-620 x 13 µm.
Microscleres : Arcuate isochelas, in two size categories: 43-67 and 21-28 µm; forceps in two size classes: 325-520 and 20-36 µm; sigmas absent (Bowerbank (1874) drew a sigma, but this supposedly was a developmental form of the chela, fide Lundbeck (1905 who re-examined the type).
Skeleton: Ectosomal skeleton a tangential mass of tylotes. Choanosomal skeleton an irregular reticulation of spicule tracts (styles).
Ecology: Deep water, 55-616 m.
Distribution: SW Ireland, Shetlands, Faroes, Norway, Sweden, Arctic.
Etymology: The name refers to the microscleres.
Type specimen information: The type is in the Natural History Museum, BMNH 1822:7:28:30 (Bk 592) (wet + 1 slide).

Remarks

This species differs from the other Forcepia species in having one of the categories of forceps very long (over 400 µm).
Source: Arndt (1935)