Mycale marshallhalli

(Kent, 1870)

Species Overview

Mycale ( Mycale) marshallhalli (Kent, 1870) is a soft cushion-shaped deep-water species occurring along most rocky coasts of Europe. Its characteristic feature is the possession of thick tylote shaped exotyles (microscopic examination necessary).

Taxonomic Description

Colour: Beige.
Shape, size, surface and consistency: Cushion or thick encrustations, 1-3 cm wide, 1 cm high. Surface hispid. Consistency soft and fragile.
Spicules: Megascleres : Styles slightly constricted near the base ("mycalostyles"), fusiform shaft: 500-800 x 16 µm; exotyles with a large but variably shaped and sized elongated tyle, protruding beyond the surface of the sponge: 800-1400 x 15-25 (tyles 35-55 µm).
Microscleres : Palmate anisochelae in two size categories: 25-40 µm and 75-90 µm (arranged in rosettes); sigmas: 13-20 µm; trichodragmas: 60-80 µm.
Skeleton: Strongly developed plumose spicule tracts, up to 150 µm in thickness, spreading out near the surface to carry a mass of tangential megascleres. Beyond that surface skeleton, individual exotyles protrude some distance.
Ecology: On rocks and dead corals in deep water, from 75 m downwards.
Distribution: Off Spain and Portugal, W coast of Ireland, between Scotland and the Faroes, Norway.
Etymology: Named after Marshall Hall, a wealthy barrister, who owned the yacht Norna , with which W. Saville Kent did dredging operations in May and June 1870 off Spain and Portugal.
Type specimen information: The type is in the Natural History Museum, London.

Remarks

The species was originally assigned to the genus Rhaphidotheca which was characterized by the possession of the peculiar exotyles. It is here considered a member of the genus Mycale , subgenus Mycale , on the authority of Hajdu (1995), who pointed out that exotyles are a functional development occurring also in other unrelated sponge groups.
Source: Stephens, 1920 (1921).