Stelletta dorsigera Schmidt (1864) is a dark red-brown, massive, often distinctly globular sponge with characteristic high ridge-like conules. In cross section it has a distinct, dark-coloured cortex and a lighter coloured inside. It is a Mediterranean species recorded from the coast of NW Spain.
Colour: Dark red-brown; inside it is light yellowish.
Shape, size, surface and consistency: Globular to massive, reaching a diameter of 10-14 cm; larger specimens usually wider than high, smaller specimens more globular. The surface is covered in conules 2-10 mm high with a broad basis, ending in paper-thin ridges, together forming almost a network (which was compared to a Surinam toad by the original author). Conules not evenly distributed nor all equally high; here and there the surface may be almost smooth. Oscules not readily visible, small. Consistency firm, hard.
Spicules: (Stelletta dorsigera spics) Megascleres: Oxeas fusiform, slightly curved, sharp-pointed: 2400-3000 x 60-70 µm; strongyles, possibly the same spicule category: 1400 x 50 µm; thick-shafted orthotriaenes (occasionally plagiotriaenes): 1160-1600 x 50-100 µm, clads 100-127 µm x 60-80 µm.
Microscleres: Ectosomal tylasters: 16 µm, with 5-8 cylindrical rays which are 4-8 µm long; oxyasters: 24 µm, with 5-10 conical rays of 10 µm long.
Skeleton: (Stelletta dorsigera skel) Cortex 3-6 mm in thickness, containing a crust of microscleres and the ends of the choanosomal bundles of megascleres. It is carried by the cladomes of the orthotriaenes. The choanosomal skeleton is radiate with thick, tightly cemented bundles of megascleres.
Ecology: At the low water mark and shallow sublittoral.
Distribution: Mediterranean, NW Spain.
Etymology: dorsum (Latin) = ridge (a.o.), referring to the ridged surface.
Type specimen information: Graz Museum LMJG 15695, Lissa, Adriatic. In BMNH several Schmidt specimens (as Astrella): BMNH 1822.214.171.124 and BMNH 18126.96.36.199 (dry) + BMNH 18188.8.131.52 (slide)—are these types?
This southern species is similar to Stelletta grubii, but differs from that in having only a single category of oxyasters (against two in S. grubii), and also in its surface characteristics.
Source: Von Lendenfeld, 1890.