Clathrina clathrus

(Schmidt, 1864)

Species Overview

Clathrina clathrus (Schmidt, 1864) is a white or yellow irregular mass of anastomosed tubes, massively encrusting to globular, but without stalk. It is a soft cushion with a smooth surface. A characteristic feature-which distinguishes it from the similar Clathrina coriacea—is the virtual absence of oscules or tube-openings; erect tubes end blindly. From the similar Clathrina contorta it can be identified with certainty on the absence of diactines and tetractines. This is a southern species occurring in the shallow sublittoral from the British Isles southwards.

Taxonomic Description

Colour: Mostly white or yellow, but brownish or reddish tinges occur also. White in alcohol.
Shape, size, surface and consistency: Irregular cushions made up of anastomosed tubes, not as tightly interwoven as Clathrina coriacea . Many contort and erect tubes, but these are all blindly ending; no visible oscules. Size 2-10 cm high and wide, individual tubes 2 mm in diameter. Surface smooth. Consistency soft.
Spicules: Calcareous. Triactines only, regular, with rays characteristically ending rather blunt: 80-100 x 6 µm.
Skeleton: Triactines are massed in the tube walls without apparent order.
Ecology: In the Laminaria-zone down to 50 m.
Distribution: British Isles, west coasts of France and Spain; Mediterranean. Reported from New Zealand and Ternate (Indonesia), but these records need verification.
Etymology: Clathrum (Greek) = lattice or grate, referring to the shape.
Type specimen information: No type material in BMNH.

Remarks

This species is closest to Clathrina coriacea , with which it shares the exclusive possession of small regular triactines. Differences are the cushion-shaped form (flat crust in coriacea ), the less tightly interwoven cormus, and the absence of a central oscule. It is also similar to C . contorta but that species has oscular tubes and also possesses both tetractines and diactines.
Source: Burton, 1963.