Placospongia decorticans

(Hanitsch, 1895)

Species Overview

Placospongia decorticans (Hanitsch, 1895) forms a thin hard crust with characteristic, raised grooves. It is a rare southern species.

Taxonomic Description

Colour: Yellowish white to greyish in alcohol.
Shape, size, surface and consistency: A thin flat crust of stony consistency, measuring 4 x 3 cm and 0.5-1 mm in thickness. The surface is raised into conules and ridges enclosing polygonal meshes. The ridges are double-walled and include deep grooves, which are expanded in live specimens.
Spicules: Megascleres : Tylostyles: 510 x 8 µm.
Microscleres : Selenasters: 80 x 28 µm in fullgrown condition, growth stages are spined rods and spiraster-like forms; spirasters: 14 µm; spherasters with a very large centre and short rays: 12 µm; spherasters with a small centre and long rays: 16 µm.
Skeleton: Ectosomal : a thick cortex consisting of a layer of selenasters covered on the outside by a layer of thick-centred spherasters. Choanosomal : pairs of bundles of tylostyles traverse the choanosome and protrude through the cortex at regular distances forming the conules. In between these bundles there is a sunken space (forming meandering grooves) containing the inhalant and exhalant openings.
Ecology: No data.
Distribution: West coast of Portugal; Mediterranean.
Etymology: The name presumably refers to the cortex-less grooves which may extend considerably in live specimens.
Type specimen information: No type material in BMNH.

Remarks

There are no sponges with which this very characteristic sponge can be confused. The selenasters superficially resemble the sterrasters of Geodia , but the possession of tylostyles easily distinguishes the present species.
Source: Hanitsch, 1895