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Heim et al. 2007

Species Overview

Tethya hibernica Heim et al. (2007) is a small yellow globular sponge of 0.5-2.5 cm in diameter, recently described from Rathlin Island, Northern Island. It differs from other North East Atlantic Tethya species by its relatively small megasters displaying frequently slightly curved tips. It is closest to T. norvegica, but this species has bifid rays on the megasters.

Taxonomic Description.

Colour: ochreous to yellow
Shape, size, surface and consistency: Body spherical, diameter 0.5-2.5 cm, clearly divided into a cortex region and a choanosomal core. Colour in alcohol white, with greyish core. Body contractile in life. Consistency compressible. Surface conulose (expanded state) to papillose (contracted state), frequently heavily loaded with sediment. Tubercles at the surface may produce filaments and stalked buds.
Spicules: Megascleres: Main megascleres are strongyloxeas, 880-1250 µm in length, 8-18 µm in diameter. Auxiliary megascleres are strongyloxeas, too, 365-820 µm in length, 7-14 µm in diameter. Microscleres: Megasters are oxyspherasters, 31-60 µm in diameter, with 13-18 rays which often slightly curve towards the tip, R/C (ratio between the length of the ray and the diameter of the centre for the spherasters) = 0.40-0.78. Micrasters fall into three catgories: mainly oxyspherasters, 10-19 µm in diameter, with 10-13 rays; strongylasters 8-18 µm in diameter, with 11-14 rays; few small tylasters, 8-10 µm in diameter, with 7-9 slightly spinulated rays.
Skeleton: Cortex compact, 0.8-1.4 mm in thickness (without tubercles), with relatively few lacunae. The radiate bundles of styles (strongyloxeas) are dense and terminate in cortical tubercles, forming terminal fans. Groups of auxiliary megascleres are present in the choanosome inbetween the main bundles. The megasters are evenly and densely scattered throughout the whole cortex. Micrasters form a discrete layer allocated to the exopinacoderm surface and the endopinacoderm of the lacunae. In addition, micrasters are evenly distributed throughout the whole cortex as well as the choanosome.
Ecology. In sheltered areas and bays.
Distribution. At present, T. hibernica has only been reported from its type localities around Rathlin Island, Northern Ireland.
Type specimen information: Holotype Mc3037 (Leg. B. Picton, 10.06.2005). Paratypes Mc2426 (Leg. B. Picton, 14.06.2005) and Mc2487 (Leg. Jen Jones, 14.06.2006). Type locality: Damicornis Bay, Rathlin Island, Northern Ireland, coordinates 55° 17.44'N 006° 15.19'W.
Etymology. Referring to 'Hibernia', the Latin denotation for Ireland.

Remarks

The closest related species seems to be T. norvegica, which shares general body characters (size, partly colour). However, T. hibernica can be clearly distinguished from T. norvegica firstly by the presence of auxiliary styles as well as the lack of bifurcated or spiny rays of the megasters. In addition the R/C values of the megasters differ between T. norvegica and T. hibernica. The morphological differences between all the European species is confirmed by extensive nucleotide and amino acid exchanges within the molecular marker COI.
Source: Heim et al. 2007

Tethya hibernica