(Carter, 1876)
Species Overview
Chelonaplysilla noevus (Carter, 1876) is a dark purple encrusting species with a very characteristic surface reticulation of sand grains visible to the naked eye or with a low magnification. There are coarse sharp conules, similar to those of Aplysilla . It is a southern species reaching its northern limits off the west coasts of France, occurring at depths of 15-115 m.
Taxonomic Description
Colour: Dark purple-violet, in life as well as in alcohol.
Shape, size, surface and consistency: Encrusting, conulose, several mm in thickness and of indefinite lateral expansion. Conules coarse, sharp, several mm apart. Surface bears a characteristic reticulation of sand grains visible to the naked eye (C. noevus surface). Oscules conspicuous, wide, slightly raised. Consistency soft.
Spicules: Absent.
Skeleton: Dendritic fibres rise from a basal spongin plate adhering the substrate, similar to the condition found in Aplysilla species. They are 75-80 µm diameter at the base, 20-30 µm near the surface. Spongin purple coloured, layered, with a wide darker area in the centre (pith). Fibres may divide a few times but seldom anastomose. Surface reticulation of sand grains with meshes of 160-170 µm diameter.
Reproduction: In the Mediterranean, violet-black larvae, with a posterior crown of long flagellae, were reported from a specimen collected on October 7.
Ecology: On rocks in the shallow sublittoral, 15-115 m.
Distribution: Roscoff, Naples, Monaco, Azores, Cape Verde Islands; a rare species in Western Europe.
Etymology: Noevus (Latin) = birthmark, referring to the shape of the type specimen according to its author.
Type specimen information: No data.
Remarks
Along the coasts of Western Europe this is the only representative of the genus Chelonaplysilla , and through its surface reticulation of sand grains is easily recognizable. In deeper waters off the Azores, C . psammophila , occurs which may be distinguished by having a much paler colour. In the Eastern Mediterranean, a third species, C . erecta , occurs which is very similar to the present species, but it forms creeping or erect branches.
Source: Topsent, 1925a (as Aplysilla arenosa ); Vacelet, 1959.