(Bowerbank, 1862)
Species Overview
Leuconia gossei (Bowerbank, 1862) is a hard white massive sponge with an optically smooth surface. Oscules are few and on top. It is a calcareous sponge and can only be confused with Leuconia nivea , which also may be massive (though mostly encrusting and thinner). The latter species has much smaller oxeas and tetractines among the spicule complement. L . gossei is a southern species reaching its northern limit along the south coasts of the British Isles.
Taxonomic Description
Colour: White/beige.
Shape, size, surface and consistency: Massive, lobed or encrusting. Surface irregular in profile. There is a rough feel to it although it is not hispid. Oscules are few in number and found at the tops of lobes. They have raised rims but no collar of spicules, and may become subfistulose. Consistency firm, brittle, hard, breaks if bent.
Spicules: (Leuconia gossei spics) Calcareous. The ectosomal triactines are symmetrical, rays: 70-100 µm; triactines of the chamber layer have rays: 70-200 µm.
The regular choanosomal tetractines have rays: 100-120 µm.
The ectosomal oxeas are large and distinctively fusiform in shape: 400-600 µm.
Skeleton: Ectosomal skelelon is a tangential layer of triactines, with oxeas which lie obliquely, without projecting beyond the surface. The skeleton of the chamber layer consists of irregularly arranged triactines, occasionally tetractines. The choanosomal skeleton is a tangential layer of tetractines which line the canals.
Reproduction: Larvae in July and August (Dubosq and Tuzet, 1942).
Ecology: This species is mainly found in the infralittoral in clean water and seems to be uncommon.
Distribution: British Isles; Atlantic coasts of France and Portugal. Probably confined to SW of the British Isles.
Etymology: Named after the collector of the type specimen, Mr Gosse of Torquay, S England.
Type specimen information: The type is in the Natural History Museum, London: BMNH 1955.11.2.42 (Bk. 297) (dry + slide). MCS Voucher BELUM: Mc12. Padstow, N. Cornwall.
Remarks
Distinctive among most other sponges in the area in having a massive, lobed growth form rather than the tubular form of most Calcarea. The texture and white coloration combined with the calcareous spicules are characteristic. Only the closely related (and very common) Leuconia nivea may be similar, but is readily distinguished by being more irregular in shape and by he absence of large oxeas; the tetractines of L . nivea are sagittal.
Source: Ackers et al., 1992 (S.M. Stone, D. Moss, B.E. Picton).