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(Cabioch, 1968)

Species Overview

Forcepia (Forcepia) psammophila (Cabioch, 1968) is a club-shaped bladder-like small (2 cm) sponge known only from a single record, at 100 m, off the north coast of Brittany. It may be distinguished from other bladder-like similar species with certainty only when examined microscopically.

Taxonomic Description

Colour: Greyish in alcohol.
Shape, size, surface and consistency: Claviform bladder-like sponge of 2 cm high and ca. 6 mm in diameter. Surface contains foreign spicules and sand grains.
Spicules: Megascleres: Exclusively tylotes, sometimes curved or lightly sinuous, with prominent heads: 210-310 x 3-4 µm. Microscleres: Arcuate isochelae of two size classes: 9-14 µm and 28-34 µm; forceps (labis) in two distinct types: one is very fine, with arms of unequal length, very numerous, length of the long arm 18-20 µm, of the short arm 6-8 µm; the other is much rarer and apparently confined to the base of the sponge, robust, spined all-over, arms of equal length, ending in a flattened knob, dimensions of arms 37-40 x 3.5 µm; sigmas of variable length, robust, abundant: 32-80 x 2-3.5 µm.
Skeleton: The ectosome bears tangential tylotes. The choanosome has bundles of tylotes which form an irregular reticulation, incorporating and agglutinating sand grains. Microscleres are distributed throughout the sponge but are particularly common in the ectosome.
Ecology: Occurred at the base of Axinella flustra, at 100 m.
Distribution: Known only from the Roscoff area.
Etymology: The name refers to the sand incorporated in the sponge.
Type specimen information: The type is in the Station Biologique de Roscoff.

Remarks

This is apparently a rare species. It differs from other Forcepia species in lacking a separate choanosomal spicule type. The tylotes are presumably ectosomal megascleres which have replaced the choanosomal megascleres. For this group of Forcepia species, Cabioch (1968) erected a separate genus Ectoforcepia, but it is not generally recognized as a valid monophyletic group.
There is a slight chance that Halichondria forcipis var. bulbosa Carter, 1876, regarded a synonym of F. forcipis, in reality was a specimen of the present species.
Source: Cabioch, 1968.

Forcepia psammophila