Iophonopsis nigricans (Bowerbank, 1858)


Family : Acarnidae

Form: Ascending finger-like growths with broader bases, cushions, massive-lobose.

Colour: Off-white, grey, through bright yellow to bright orange, blackening on contact with air and on preservation.

Smell: None.

Consistency: Fairly soft and crumbly.

Surface: Irregular, with raised areas of denser appearance supported by the underlying skeleton, with a transparent surface membrane between these ridges.

Apertures: Oscules are slightly raised, with transparent rims, and are found along the edges of the fingers and on raised ridges of lobed form.

Contraction: Oscules disappear and surface membrane collapses on removal from water.

Internal characters

Skeleton: A fairly regular mesh of acanthostyles which is reminiscent of Myxilla spp. There are dense bundles of tornotes lying tangentially and at an angle to the surface. Bipocilles and anisochelae are scattered throughout the body with small anisochelae more abundant at the surface.

Spicules: Acanthostyles (a) stout, typically 220-(240)-260m long; tornotes (b) with swollen microspined ends, stout, 240-(245)-250m long. Anisochelae (c) ca. 26m and 10m. Bipocilles (d) small ca. 7.5m.

Habitat: Found in sheltered or moderately exposed sites, with moderate to strong tidal streams. On rocks, boulders, steep rockfaces and shells. Circalittoral. Common on brachiopod valves in Firth of Lorne.

Distribution: Common and widespread in the English Channel, Ireland and W. Scotland.

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

Identity: The blackening on death is very noticeable, and the bipocilles and tornotes with microspined ends are characteristic. Larger specimens may resemble Myxilla incrustans or Myxilla rosacea superficially.

Voucher: BELUM : Mc1182. Maidens, Antrim.

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

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