Polymastia agglutinans

Ridley and Dendy, 1886

Species Overview

Polymastia agglutinans Ridley and Dendy, 1886 is a small Polymastia species with only a few papillae. Its characteristic is the foreign material (shell debris, sand etc.) that adheres to the surface, which is otherwise smooth.

Taxonomic Description

Colour: Yellow to orange.
Shape, size, surface and consistency: Cushion with a few papillae. Size 1-3 cm in diameter, papillae may reach 2 cm in length. Surface encrusted by numerous fragments of shells, grains of sand, etc. Consistency firm.
Spicules: Tylostyles in three categories: principal style-like tylostyles which constitute the bundles of the choanosomal skeleton and of the papillae: 1200 x 16 µm; intermediate forms which constitute the tangential layer (no size recorded); and small tylostyles of the suface palisade: 175 x 4 µm.
Skeleton: (Polymastia agglutinans cross) The presence of the foreign objects at the surface modifies the architecture of the skeleton of the cortex: the palisade of ectosomal small tylostyles can only be observed between the incorporated fragments, and also the subectosomal tangential layer is often dispersed or absent. The choanosomal bundles of large tylostyles are unaffected. The papillae have the same architecture as those of P . mamillaris . The surface of the exhalant canal is echinated by ectosomal tylostyles.
Ecology: Sandy-pebbly bottoms, rare at 27 m, more common beyond 50 m.
Distribution: Plymouth, Roscoff; elsewhere it occurs off the Azores and along the west coast of Africa.
Etymology: The name refers to the pieces of shell and pebbles adhering to the surface.
Type specimen information: The type is in the Natural History Museum, London: BMNH 1887.5.2.83 (wet + slide), Challenger Stn. 75.

Remarks

The distinguishing characters are the fine papillae and the shell debris adhering to the surface.
Source: Boury-Esnault, 1987.