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(Barrois, 1876)

Species Overview

Aplysilla rosea (Aplysilla sulfurea/rosea) (Barrois, 1876) are thinly encrusting red or yellow coloured sponges with a typical "goose flesh" surface of low conules. These conules are caused by protruding single fibres, which start at the basal spongin plate and run towards the surface, giving off occasional branches at sharp angles but not anastomosing. These sponges are common under boulders in the intertidal region.

Taxonomic Description

Colour: Pale yellow to bright sulphur yellow ("A. sulfurea" Aplysilla rosea sulphurea) or brick red or deep red ("A. rosea").
Shape, size, surface and consistency: Thin, soft, brightly coloured incrustations, up to 40 mm in extent and 5 mm in thickness, with the surface uplifted into low conules 0.5 mm high (up to 2-3 mm) by internal, upright, horny fibres spaced roughly 0.8 to 1.6 mm (even to 5 mm has been reported) apart. Surface smooth in between conules. In expanded sponges one sees a network of which the polygonal areas are membraneous and pierced by groups of ostia. One to several oscules, often mounted at the ends of oscular chimneys, 1-3 mm wide. Contractile tissue is present in the soft matrix and lines the pores, canals and oscular chimneys. Consistency soft and compressible. No smell reported.
Spicules: Absent.
Skeleton: The sponge is supported by upright horny fibres rising from the basal plate of spongin (Aplysilla cross section). These fibres may branch at intervals, and the branches can likewise branch, but adjacent fibres do not coalesce or anastomose to form a network (i.e. they are dendritic). The branches and stems are round in cross-section and have rounded tips. The fibres have a distinct core or pith making up about 8/10 to 9/10ths of the total thickness, which is covered by thin layers of spongin. In longitudinal section both pith and superficial layers can be seen to be built up like a stack of thimbles, one over the next lower down. The fibres are generally 0.06 to 0.1 mm thick at their base (even 0.3 mm is reported) and 0.02 mm or more thick distally. They are flexible and elastic when isolated. They do not contain foreign matter, such as embedded sand grains or broken spicules.
Reproduction: May to August; larvae are yellow with a pigmented posterior pole, scarcely ciliated but with a longer ring of cilia near the posterior pole, size 500 x 880 µm (Delage, 1892; Lévi, 1956; Wapstra and Van Soest, 1987).
Ecology: On under-surfaces of stones on the shore; on rock and stones below low water. Depth distribution: littoral to 640 m depth (var. rosea); to 320 m depth (var. sulfurea).
Distribution: Atlantic; North Sea; Sweden; Ireland; Channel; Mediterranean).
Type specimen information: probably in MNHN; MCS voucher BELUM Mc587.


The colours, conulose surface, branching, non-anastomosing horny fibres and absence of spicules are diagnostic. Two closely related genera are Chelonaplysilla, with a conulose surface reinforced by a network of foreign matter visible to the eye; and Pleraplysilla, with an Aplysilla - like conulose surface but with the dendritic fibres cored by foreign matter.
Hexadella racovitzai is superficially similar, but this species has no skeleton (no fibres).
Schulze (1878) could not decide whether these two colour forms were distinct species or belonged to the same species, because structurally they were very alike. He also thought that his A. rosea could be the same as Verongia rosea Barrois, 1876. Vacelet, 1959 regarded them as a single species, but Bergquist, 1980 treats them as separate species. It is important always to record the colour 'morphs', because they appear to vary in distribution and relative abundance from place to place, for reasons so far unexplained. Until the situation is clarified it will be useful to retain the names sulfurea and rosea.
Sources: Ackers et al., 1985, 1992 (S.M. Stone and D. Moss), W. Clifford Jones.

Aplysilla rosea