Spirastrella minax

(Topsent, 1888a [1887])

Species Overview

Spirastrella minax (Topsent, 1888a [1887]) is yellowish or red, hispid encrustation with a firm consistency. It can only be reliably identified by its chracteristic microscleres (microscopic examination). It is a rare species recorded from NW France and the Mediterranean.

Taxonomic Description

Colour: Red, rose, ochre-yellow or pale yellow.
Shape, size, surface and consistency: Thin encrustation with hispid surface. No size data recorded, but it forms only small patches. No obvious oscules. Consistency firm.
Spicules: Megascleres : Tylostyles, smooth, slightly curved, with globular or oval heads, of variable size: 200-700 x 2-13 µm.
Microscleres : Spirasters with a strong spiralization (presenting 3 angles in an optical cross section), strongly spined, especially on the outward curves and at the ends: 20-25 x 3-4 µm.
Skeleton: Tylostyles erect on the substrate, points upward, protruding beyond the surface; at the periphery there is a thick layer of microscleres.
Ecology: On rocks in deep water, 55-300 m.
Etymology: Minax (Latin) = jutting out, referring to the hispid surface.
Distribution: NW France; Mediterranean.
Type specimen information: The type is in the Muséum National d'Histoire Naturelle, Paris.

Remarks

This is the only species of Spirastrella in the area. Spiculation of Cliona species may be similar, but these have surface papillae.
Source: Topsent, 1900.