Hymerhabdia typica Topsent, 1892


Family : Raspailiidae

Form: Thinly encrusting, forming sheets 5-10 cm or more in extent.

Colour: Yellow, reported in the literature also as dark orange.

Consistency: Thin fragile crust.

Surface: Bumpy, slightly hispid, with a granular appearance in undisturbed specimens.

Apertures: Oscules small, with transparent rims. Branching excurrent channels visible through the surface, converging on oscules.

Contraction: Some contraction of the surface and oscules on disturbance.

Internal characters

Skeleton: The large tylostyles are erect on the substrate, with their heads embedded in a layer of rhabdostyles and curved oxeotes.

Spicules: Tylostyles, smooth, straight, with well-developed heads: 500-800 x 3-13 Ám. Rhabdostyles and centrotylote oxeas, smooth, strongly recurved and spirally twisted: 120-300 x 4-5 Ám.

Habitat: On boulders and bedrock in strong to moderate tidal streams, open coast.

Distribution: Mediterranean, Azores, Roscoff. Occasional at Rathlin Island, Co Antrim, Northern Ireland.

Distribution Map: NBN map : National Biodiversity Network mapping facility, data for UK.

Identity: This species differs from its congener H . intermedia in the smaller rhabdostyles and the possession of centrotylote oxeas instead of strongyles. The latter are less strongly curved.

Editors: Christine Morrow, Bernard Picton & Rob van Soest.

 Picton, B.E., Morrow, C.C. & van Soest, R.W.B., 2011. [In] Sponges of Britain and Ireland