Bowerbank, 1874
Species Overview
Polymastia conigera Bowerbank, 1874 is a small cream-coloured Polymastia , similar to P . mamillaris but much more hispid, the papillae are simultaneously exhalant and inhalant and its larger tylostyles are polytylote. It is a rare species, so far recorded only twice.
Taxonomic Description
Colour: Cream.
Shape, size, surface and consistency: Encrusting like P . mammillaris , but smaller. A specimen from the Channel area recorded by Cabioch is 3.5 cm long, 1.5 cm large and 0.5 cm thick. There are eight very conical papillae about 2 cm long. The surface of the body is very hispid. Consistency firm.
Spicules: (Polymastia conigera Bow.) The principal and intermediary tylostyles are polytylote. The central canal of the spicule is straight without any dilatation at the level of the swelling. Principal tylostyles: 1196-1533 x 16-30 µm; intermediary tylostyles: 516-780 x 10-16 µm; ectosomal tylostyles, with an asymmetric and tapering point: 110-130 x 3-5 µm.
Skeleton: (Polymastia conigera cross) Ectosome : The cortex is 290 µm thick. Its skeleton is composed of a palisade of ectosomal tylostyles, the basis of which is embedded in a layer of tangential tylostyles 200 µm thick. Choanosome : the choanosomal skeleton is composed by bundles of principal tylostyles of 300 µm in diameter. The ends of these bundles pass through the surface. Intermediary tylostyles are loose between the bundles. Papillae : all the papillae are simultaneously inhalant and exhalant. The exhalant canal is central and the inhalant canals are distributed around it. The thickness of the wall is approximately 600 µm. The longitudinal bundles of tylostyles are located within the wall between the inhalant canals. They are linked by a dense, irregular network of intermediary tylostyles, which echinate the surface of the canals. Near the surface, the same arrangement as in the ectosome is found, i.e. a tangential layer of intermediary tylostyles and a palisade of small tylostyles.
Ecology: Sandy areas, on shells including those inhabited by Phascolion strombi , 15-85 m.
Distribution: Described by Bowerbank from Shetland, it was found in the Channel near Roscoff. Dendy (1921) and Bergquist (1968) described this species from the Indian Ocean and New Zealand. Boury-Esnault (1987) is not convinced that their record is OK, as the shape of the sponge and the size of the spicules differ from those of the type.
Etymology: The name refers to the cone-shaped papillae.
Type specimen information: The type is in the Natural History Museum, London.
Remarks
There is no recent description of the Atlantic P . conigera . The type specimen from Bowerbank, which appears to be a fragment, and a specimen from Cabioch collected in the Channel (NW of Ile de Batz), are the only specimens available. The distinguishing feature of this sponge is the polytylote nature of the large tylostyles.
Source: Boury-Esnault, 1987.