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Bowerbank in Norman, 1869

Species Overview

Hymedesmia (Hymedesmia) occulta Bowerbank in Norman (1869) is a thinly encrusting deep-water sponge, of which the live colour so far is not known. It has characteristic spiculation (microscopic examination). It is a northern species.

Taxonomic Description

Colour: Whitish grey or brownish in alcohol; white in dry condition.
Shape, size, surface and consistency: Thinly encrusting. Largest lateral expansion up to 20 mm; thickness 1 mm. Surface smooth but provided with long osculiferous papillae of up to 15 mm (not recorded in the original description). Consistency: soft.
Spicules: Megascleres: Ectosomal tornotes oxeote, fusiform: 340-500 x 8-13 µm; large acanthostyles with spines only on the head and the shaft close to it: 470-1190 x 25-37; small acanthostyles, entirely spined: 120-260 x 20-25 µm. Microscleres: Arcuate chelae, strongly curved: 34-40 µm.
Skeleton: Hymedesmoid.
Ecology: Deep water, on Lophelia, 80-2000 m
Distribution: North Atlantic: off Iceland, Scotland Shetlands, SW Ireland, Roscoff, Azores.
Etymology: The name refers to the inconspicuous habit.
Type specimen information: BMNH 1910:1:1:90 (dry) Norman Collection + slides unregistered (Bk.472).


The characteristic feature of the species are the thick fusiform tornotes and the length of the large acanthostyles.
Source: Lundbeck, 1910.

Hymedesmia occulta