Sarà and Siribelli, 1960
Eurypon major Sarà and Siribelli (1960) is one of several thin red encrusting species, difficult to recognize on field characters. Along with Hymeraphia stellata and Eurypon lacazei, it is characterized by isolated spicules sticking out 1-1.5 mm beyond the surface, visible to the naked eye. (other red crusts, e.g. Clathria spp. are less obviously hispid). For a definite identification microscopic examination is necessary: this is the only Eurypon with thick ectosomal oxeas. The species was described originally from the Mediterranean, but is reported as locally common on several places along the Western European coasts.
Colour: Vivid red.
Shape, size, surface and consistency: A thin (to 0.5 mm) crust overgrowing rock surfaces, with an uneven, bubbly appearance. Surface villose with long fine styles and shorter fine oxeas penetrating the surface. The spicules penetrating the surface may trap silt. Apertures scattered inconspicuous. Oscular rims are transparent with small blobs of red tissue. Consistency hard to describe since a very thin crust.
Spicules: (Eurypon major spics) Three categories of megascleres are found: oxeas, tylostyles and acanthostyles. Fairly stout ectosomal oxeas, occasionally with rounded proximal ends: ca. 385-525 x 3-7 µm. Choaonosomal tylostyles: 1440-2210 x 10-17 µm. Entirely spined acanthostyles: ca. 85-165 µm (? up to ca. 125-164 µm).
Skeleton: Eurypon spp. all have skeletons with acanthostyles arranged perpendicular to the substrate and with their heads resting on the substrate. Long tylostyles, also perpendicular to the substrate with heads in the basal spongin layer, are scattered amongst the acanthostyles. Where these tylostyles penetrate the surface they end in a brush or fan of fine styles or oxeas. In Eurypon major these ectosomal spicules are oxeas
Ecology: Rocky surfaces. Common on vertical surfaces in Lough Hyne, SW Ireland, and on offshore pebbles in the Roscoff area down to at least 40 m.
Distribution: North and west coasts of Ireland, N coast of Bretagne; originally described from the Mediterranean.
Etymology: The name refers to the long tylostyles.
Type specimen information: Presumably in the Istituto e Museo di Zoologia dell'Università di Napoli; MCS Voucher BELUM: Mc1338. Lough Ine, Cork, Ireland.
All Eurypon spp. are thin crusts and several are red. Eurypon and Hymeraphia stellifera (and allied species) can be distinguished from other red crusts by the very long tylostyles that project 1 to 1.5 mm through the surface. The larger dimensions of the oxeas distinguishes this species from Eurypon lacazei. Possibly, the specimen quoted by Stephens (1921) as E. lacazei may belong to the present species. Other Eurypon species have different ectosomal spicules or these are apparently absent (in E. coronula).
Sources: Sarà and Siribelli, 1960; Ackers et al., 1992 (B.E. Picton, D. Moss).