Polymastia inflata

Cabioch, 1968

Species Overview

Polymastia inflata Cabioch, 1968 is a small rather thin cushion with 1-3 papillae of 1.5 cm long. It is pale yellow in colour. It is a southern species reported from Roscoff, Galicia and the Mediterranean.

Taxonomic Description

Colour: Pale yellow.
Shape, size, surface and consistency: Encrusting, small and not very thick, about 2 cm2, with one to three cylindrical papillas of 1.5 cm high.
Spicules: Three types of tylostyles: principal tylostyles are in fact fusiform strongyloxeas, with somewhat deformed head: 620-1250 x 11-18 µm; intermediary tylostyles fusiform, with a well-rounded head: 250-660 x 11-26 µm; ectosomal tylostyles with well-rounded head, slightly fusiform: 90-290 x 3-5 µm.
Skeleton: (Polymastia inflata skel) The ectosomal cortex is ca. 600 µm thick. It is made up of a dense layer of tangential tylostyles upon which a palisade of small tylostyles rests. The choaonosomal skeleton consists of bundles of tylostyles ca. 250 µm in diameter. Between these bundles intermediary and ectosomal tylostyles are loosely dispersed. The papillae are simultaneously inhalant and exhalant. The exhalant canal is surrounded by the inhalant ones. Bundles of tylostyles lie at the periphery underneath a layer of tangential tylostyles and the palisade of ectosomal tylostyles. Free fusiform tylostyles lie between the canals in the cellular laminae.
Ecology: Sandy areas, on rocks and on shells of gastropods inhabited by Phascolion strombi , from 15-150 m.
Distribution: Roscoff, Galicia, Mediterranean, West Africa.
Etymology: The name refers to the inflated body in living condition.
Type specimen information: The type is in the collections of the Station Biologique, Roscoff.

Remarks

The fusiform tylostyles are rather distinctive.
Source: Boury-Esnault, 1987.