Aplysilla sulfurea Schulze, 1878


Family : Darwinellidae

Form: Thin, soft, brightly coloured incrustations, up to 40mm in extent, and 5mm in thickness, with the surface uplifted into low conules 0.5mm high (up to 2-3mm) by internal, upright, generally branching, horny fibres spaced roughly 0.8 to 1.6mm (even to 5mm has been reported) apart.

Colour: Pale yellow to bright sulphur yellow.

Smell: None reported.

Consistency: Sponge soft and compressible.

Surface: Smooth in between conules. In expanded sponges one sees a network of which the polygonal areas are membranous and pierced by groups of ostia.

Apertures: One to several oscules, often mounted at the ends of oscular chimneys, l-3mm wide.

Contraction: Contractile tissue is present in the soft matrix and lines the pores, canals and oscular chimneys.

Internal characters

Skeleton: No spicules are present. The sponge is supported by upright horny fibres rising from the basal plate of spongin. These fibres may branch at intervals, and the branches can likewise branch, but adjacent fibres do not coalesce to form a network (i.e. skeleton is dendritic). The branches and stems are round in cross-section and have rounded tips. The fibres have a distinct core, making up about 8/10 to 9/10ths of the total thickness, which is covered by thin layers of spongin. In longitudinal section both core 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 0.1mm thick at their base (even 0.3mm is reported) and 0.02mm or more thick distally. They are flexible and elastic when isolated. They do not contain foreign matter, such as embedded sand grains or spicules.

Spicules: none

Habitat: On under-surfaces of stones on the shore; on rock and stones below low water. Under overhangs and in caves, generally out of bright light.

Distribution: Littoral to 320m depth. Atlantic; North Sea; Channel; Mediterranean; etc.

Distribution Map: NBN map : National Biodiversity Network mapping facility, data for UK.

Identity: The colour, conulated surface, branching, non-anastomosing horny fibres and absence of spicules are diagnostic. Two closely related genera are Chelonaplysilla, with a conulate surface reinforced by a network of foreign matter visible to the eye; and Pleraplysilla, with an Aplysillid-like conulate surface but with the dendritic fibres covered by foreign matter. Both have been found at Roscoff and can be expected to be found in the British Isles.

Voucher: BELUM : Mc963

Editors: D. Moss, B.E. Picton.

 Picton, B.E., Morrow, C.C. & van Soest, R.W.B., 2011. [In] Sponges of Britain and Ireland