Phorbas plumosum (Montagu, 1818)


Family : Hymedesmiidae

Form: A thin cushion, typically 5mm to 1cm thick, spreading in patches of diameter typically ca. 6cm. It may become massive-lobose in sheltered locations.

Colour: Variable: "scarlet", orange to dirty violet-brown.

Smell: A strong smell, variously described as like iodine or 'garlic on breath'; or (?) 'like Amphilectus'.

Consistency: Somewhat crumbly, compressible and fairly resilient.

Surface: More or less smooth or somewhat tuberculate or "conulate", with transparent tissue between the tubercles.

Apertures: Oscules "small", scattered, "numerous" and obvious; they may be in groups. Excurrent channels are present.

Contraction: Slight. (There is a tendency to 'curl up' on removal from the water).

Internal characters

Skeleton: A plumose skeleton of ascending multi-spicular fibres of acanthostyles, echinated by smaller acanthostyles. There is a well developed ectosomal skeleton of tornotes arranged in vertical brushes. Spongin is scarce.

Spicules: Megascleres of the main skeleton are large acanthostyles (a), 180-(200)-240Ám, sparsely spined and echinated by smaller acanthostyles (b), 80-(110)-140Ám, which are densely and entirely spined. The ectosomal tornotes (c) have oxeote ends and are 160-(170)-185Ám in length. The microscleres are arcuate isochelae (d) of distinctive shape, small and fine, ca. 15Ám.

Habitat: Common. Typically found in shallow water - the kelp zone, especially in highly exposed sites, and in 'rapids' situations on upper surfaces of rocks. It may also occur in semi-sheltered situations with moderate current. "Littoral to 680m."

Distribution: "Faroes; British Isles; Atlantic coasts of France and Spain; Portugal; etc." Recently known from Tiree, St Kilda, W. Scotland; Strangford Lough; Lough Hyne; Saltee Is., Co. Wexford; Co. Galway; N. and W. Cornwall; Anglesey; Sussex; Jersey.

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

Identity: The smell and appearance are fairly characteristic, but there are several other species of Stylostichon whose living characters are not known, as well as the others described here. The spicule complement with only one size of chela and no sigmata is characteristic of S. plumosum.

Voucher: BELUM : Mc525. Saltee Islands, Wexford.

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

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