Sycon raphanus

Schmidt, 1862

Species Overview

Sycon raphanus Schmidt, 1862 is an oval or globular tube-shaped calcareous sponge with a hairy surface. It is similar to S . ciliatum but differs in having choanocyte chambers fused over much of their length (histological preparation necessary).

Taxonomic Description

Colour: White, grey or yellow.
Shape, size, surface and consistency: Globular to fusiform, with a terminal oscule surrounded by a fringe of stiff spicules. Height up to 8 cm, diameter up to 2.7 cm; may occasionally have a short stalk. Surface hairy or hispid. Consistency soft.
Spicules: (Sycon raphanus spics) Calcareous. Triactines: rays 100-250 x 8-12. Tetractines of the atrial skeleton: similar to triactines, with apical rays of 60-120 µm.
Oxeas: 1000-3000 x 20-24 µm.
Skeleton: Tubar skeleton of triactines with distal cones with brushes of oxeas; atrial skeleton of triactines and tetractines.
Choanocyte chambers: Fused over almost their entire length, excepting the distal cones.
Reproduction: August.
Ecology: Intertidal caves and among weeds in rock pools in exposed habitats; under stones in the littoral; on vertical cliffs; sublittoral down to 70 m.
Distribution: Norway, Faroes, W Ireland, Roscoff, Iles de Glénan, Galicia; Mediterranean.
Etymology: Raphanus (Greek) = radish, presumably referring to the shape of the sponge.
Type specimen information: The types are in the Natural History Museum, London, BMNH 1867:7:26:5 (cotype-wet) and BMNH 1867:3:11:75 (Schmidt slide).

Remarks

This is very similar to Sycon ciliatum in spiculation, but a major difference is found in the degree of fusion of the choanocyte chambers (radial tubes). In S . raphanus these are almost entirely fused just up to the distal cone, whereas in S . ciliatum the choanocyte chambers are entirely free from each other.
Source: Arndt, 1935