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(Bowerbank, 1866)

Species Overview

Clathria (Microciona) laevis (Bowerbank, 1866) is a thin cream-coloured crust with clear channels visible on the surface in situ. Among the many Clathria crusts this species stands out by the colour and the lack of palmate isochelae.

Taxonomic Description

Colour: cream.
Shape, size, surface and consistency: Thin crust approximately 5 cm in diameter. The surface has obvious excurrent channels converging on transparent osculae which are not raised above the surface. The whole surface between the channels is covered with small ostia.
Spicules: Megascleres: Ectosomal styles: 340-750 by 2-3 µm, smooth with a slightly tylote head. Long smooth styles: 350-1000 by 8-10 µm, no development of the head. Acanthostyles: 65-240 by 4-8 µm, slightly tylote head, entirely spined with small spines. Microscleres: Toxas: 50-80 by 0.5-3 µm, distinctively shaped, with a small central flexion and thickened in the mid portion, similar to those of Ophlitaspongia kildensis Howson & Chambers (1999). The majority are in the thicker part of the range but there are also some very thin, hair-like, toxas.
Skeleton: Two categories of styles projecting from the basal layer of spongin. The larger styles project beyond the surface of the sponge. There are brushes of the ectosomal styles at the sponge surface. Numerous toxas are scattered through the choanosome.
Ecology: Vertical surfaces, 28-33 m.
Distribution: Shetland, W coast of Ireland, Northern Ireland, Iceland, Sweden.
Etymology: from the Latin laevis meaning smooth.
Type specimen information: The type is in the Natural History Museum.


In Northern Ireland, one specimen was found on vertical steel plates of the 'Lochgarry' wreck off Rathlin Island. There are few prior records, it seems to be mainly a northern species. First described by Bowerbank (1866) from Shetland. Recorded by Stephens (1917) from the west coast of Ireland and Vosmaer (1935) and Burton (1959) from Iceland. Also from the Skager Rak (fairly common) and Vaderø Fjord (common 50-70 m) in Sweden (Alander, 1942).
There are at least four species of Clathria along the coasts of Western Europe lacking chelae; these are in need of critical revision.
Source: Picton & Goodwin, 2007.

Clathria laevis