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(Topsent, 1893)

Species Overview

Hymedesmia (Hymedesmia) versicolor (Topsent, 1893) is a thinly encrusting Mediterranean species reported also from the Atlantic coasts of France. It is possible that the latter records concern Hymedesmia (H.) paupertas, because they are reported as bluish or greenish. Further research is necessary.

Taxonomic Description

Colour: Greenish or blue (Western Europe); also reported as yellow (Mediterranean).
Shape, size, surface and consistency: Thinly encrusting. Areolate porefields slightly raised, rounded, visible as lighter areas.
Spicules: Megascleres: Tornotes anisotylote, may be polytylote: 235-325 x 2-5 µm; large acanthostyles, spined mainly near the head: 260-460 x 5-11 µm; small acanthostyles, entirely spined: 115-180 x 2-5 µm. Microscleres: Arcuate isochelae with short alae: 24-32 µm.
Skeleton: Hymedesmoid: acanthostyles erect on the substrate; bundles of ectosomal tornotes.
Ecology: On stones, in caves, in deeper water below 20 m.
Distribution: Mediterranean, Roscoff, Le Portel (Straits of Dover).
Etymology: The name refers to the variable live colour.
Type specimen information: The type is in the Paris Museum.

Remarks

The blue specimens are indistinguishable from Hymedesmia (H.) paupertas (Bowerbank) and thus part of the material ascribed to H. versicolor (including the Western European specimens) may belong to that species.
Source: Topsent (1936).

Hymedesmia versicolor