Plakina monolopha Schulze, 1880


Family : Plakinidae

Form: A loosely adhering crust with irregular roundish or lobate borders. Thickness several mm. Frequently the crusts have irregular holes as if lobes have encircled a bare part of the substratum.

Colour: White, delicately rose, ochre-yellow, brown or rose-brown. The colour of this species is related to exposure to light: the more light the darker the colour.

Consistency: Crisp.

Surface: Under low magnification a system of gently curved slits or pits is visible.

Internal characters

Skeleton: Alveolar arrangement around the large eurypylous choanocyte chambers. Lophocalthropses usually concentrated at the surface.

Spicules: Small calthropses, triods and diods, no proper microscleres (although the size of the "megascleres" is small). Calthropses (lophocalthrops or lophotriaene) have one lophate ray with two to five proliferations; triods are equiangular or Y-shaped; diods have a clear central irregular knot. Rays of calthropses and triods: 25-30 x 2-3. Diods: 70-90 x 3-4 Ám.

Habitat: Under stones and boulders in shallow water, 10 m.

Distribution: Ireland, west coast of France and Spain; Mediterranean.

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

Identity: With low magnification the characteristic surface depressions can be easily observed. The only species with which it may then be confused is Plakortis simplex. This is easily distinguished by the lack of (lopho-)calthropses.

Editors: Christine Morrow, Bernard Picton & Rob van Soest.

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