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Picton & Goodwin, 2007

Species Overview

Hymeraphia elongata Picton & Goodwin (2007) is a thin yellow hispid crust on rocks. Very similar to congeneric species H. stellifera and H. breeni. Microscopic examination and measurement of spicules is necessary to identify this species with certainty. So far, only known from Northern Ireland.

Taxonomic Description

Colour: Yellow.
Shape, surface, size and consistency: Hispid, thin, non-descript crust.
Spicules: Tylostyles: 260 - 1450 by 5 - 12 µm. Tylote head, similar in form to that of the acanthostyles. Sometimes shaft near head is straight but most often slightly curved. Ectosomal spicules: 300 -330 by <0.5 -2.5 µm. Very thin hair-like spicules. Head rounded but not tylote, tapering to the other end which is often rounded-strongyle in form. Acanthostyless: 90 - 145 by 7 -10 µm. Base tylote and slightly curved. Tip spined but spines are often poorly developed, small and rounded. Most aretowards the larger end of this size-range, only a few short ones are present. Occadionally acanthostyles like those of H. stellifera are present.
Skeleton: Hymedesmoid with heads of tylostyles and acanthostyles embedded in a thin basal layer of spongin. The longer tylostyles penetrate the surface of the sponge and the ectosomal spicules form bouquets around their points. The ectosomal spicules are asymmetrical with the thicker end being embedded in the sponge surface.
Distribution: So far known only from Rathlin Island, Northern Ireland.
Ecology: On rocks at 29-34 m.
Etymology: From the latin elongat meaning long, named for the elongated acanthostyles.
Type material: Holotype: [Mc3129]. Sample in IMS, section and spicule preparation; Damicornis Bay (55°17.429'N 006°15.098'W; water depth: 29–34 m); coll. by J.J. and L.S., 16 August 2005.

Remarks

This is distinguished from both Hymeraphia stellifera and H. breeni by the long length and narrower width of the acanthostyles and the form of the spines at their tips. It is yellow in colour whereas H. breeni is always orange, however, some yellow specimens of H. stellifera were collected so colour is not likely to be a reliable characteristic. It does not have the papillae with oscules on their ends that are typical of the two other Hymeraphia species. One specimen was collected from a stable boulder.
Source: Picton & Goodwin, 2007

Hymeraphia elongata