Hymedesmia peachi

Bowerbank, 1882

Species Overview

Hymedesmia peachi Bowerbank, 1882 is a very thinly encrusting yellow smooth sponge, growing on undersides of stones or on shells. It has apparently a wide distribution between the north of the British Isles and the Mediterranean.

Taxonomic Description

Colour: Yellow, orange or sometimes maroon.
Shape, size, surface and consistency: Very thinly encrusting, with smooth or minutely hispid surface. Size up to several cm2. No obvious oscules. Consistency soft.
Spicules: (Hymedesmia peachi spics) Megascleres : Ectosomal tornotes slender, straight, with bluntly oxeote ends: 169-248 x 3 µm; acanthostyles not easily divisible into two categories, spined for the greater part of their length, but smooth in the distal portion, spining particularly strong near the base: 68-395 x 12-22 µm.
Microscleres : Arcuate isochelae, variable in shape, probably divisible in two size categories: 14-20 and 24-38 µm.
Skeleton: Irregular, but presumably hymedesmoid with long acanthostyles erect on the substrate; tornotes in bundles.
Ecology: In sciaphilous biotopes, under stones, in caves, 5-20 m.
Distribution: Northern England, Roscoff, Mediterranean.
Etymology: Named after the collector of the type specimen, Mr Peach of Scotland.
Type specimen information: The type is in the Natural History Museum, London.

Remarks

The species differs from similar Hymedesmia spp. in the possession of two size categories of microscleres.
Source: Boury-Esnault, 1971