Psammopemma finmarchicum

Hentschel, 1929

Species Overview

Psammopemma finmarchicum Hentschel, 1929 is a thinly to massively encrusting, finely conulose sponge. Live colour not recorded, but dried specimens are orange-grey. The species is characterized by having non-anastomosed columns of sandgrains as skeletal material (can be observed with the naked eye). It is a northern species.

Taxonomic Description

Colour: In dry specimens: orange grey (grey in alcohol).
Shape, size, surface and consistency: Massive encrustations with faintly rugose surface. Size up to 5 x 10 cm, at least 3 mm in thickness. Surface covered in small conules, 0.5-1 mm high spaced 1 mm apart. Oscules few in number, 1-2 mm in diameter. Consistency firm, crumbly.
Spicules: Absent.
Skeleton: The skeleton consists entirely of sand grains arranged in thick columns up to 850 µm in diameter, rising from the substrate. These are irregularly and sparingly connected by thin sand "fibres". The interior is often completely filled with sand grains. No visible spongin. Surface skeleton a more or less continuous layer of fine sand grains.
Choanocyte chambers: Oval and 70 µm long.
Ecology: In fjords, 50-200 m.
Distribution: Norway.
Etymology: Finmarken is the northernmost region of Norway.
Type specimen information: No data.

Remarks

This species may be confused with Dysidea and Hyrtios species, but in these there is always some recognizable spongin and the fibres are arranged in a rectangular system of primary fibres and interconnecting secondary fibres. Pleraplysilla also shows some spongin nad has distinctly tapering fibres, thick near the substrate, thinning out towards the surface. Surface conules in all these genera are coarser than in the present species.
Some authors consider Psammopemma a member of the Poecilosclerida, but the size of the choanocyte chambers conforms to that found in Dendroceratida.
Source: Hentschel, 1929.