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(Topsent, 1892b)

Species Overview

Myxilla (Myxilla) iotrochotina (Topsent, 1892b) is a yellowish, encrusting sponge with an irregular, somewhat slimy surface. It needs to be examined microscopically for a certain identification; the shape of its anchorate isochelae is unique among the Myxilla species of the area.

Taxonomic Description

Colour: Yellowish or ochre.
Shape, size, surface and consistency: Thinly encrusting, irregular surface, somewhat slimy, fragile consistency.
Spicules: Megascleres: Tornotes, straight or slightly curved, slightly fusiform, with three or two sharp teeth at both ends: 125-155 x 3 µm (Topsent, 1936a) (Descatoire, 1969b: 100-110 x 5-6 µm) (Durán and Solórzano, 1982: 475-533 µm); acanthostyles, overall spined: 100-115 x 5 µm (Topsent, 1936a) (Descatoire, 1969b: 90-124 x 6-8 µm) (Durán and Solórzano, 1982: up to 547 µm).
Microscleres: Anchorate/unguiferate isochelae with straight shafts and 3-5 teeth: 13-15 µm (Topsent, 1936a) (Durán and Solórzano, 1982: 37-48 µm); sigmas: 15-35 µm (Topsent, 1936a) (Durán and Solórzano, 1982: two sizes, one 33-40 µm, the other 55-74 µm).
Skeleton: Unispicular reticulation of acanthostyles; tornotes in brushes at the surface.
Ecology: On shells and coralline algae and on Laminaria, in the sublittoral.
Distribution: Iles de Glénan, Galicia, Asturia; Mediterranean.
Etymology: The name refers to the birotulate-like chelae; Iotrochota is characterized by possession of birotulates as the only microscleres.
Type specimen information: The type is in the Muséum National d'Histoire Naturelle, Paris.


The chelae bear 5 teeth and have a straight shaft making them resemble those of Plocamiancora; they are not, however, true birotulates as found in Iotrochota. Tornotes are rather similar to those of Myxilla rosacea. The discrepancies in spicule sizes quoted by Topsent (1936) / Descatoire (1969) and Durán and Solórzano (1982) are too large to be the product of variation. The sizes quoted by the latter authors are likely to be misprints, or these records concern two different species.
Source: Topsent (1936)

Myxilla iotrochotina