Hexadella topsenti Reveillaud, Allewaert, Pérez, Vacelet, Banaigs & Vanreusel, 2012


Family : Ianthellidae

Form: Previously reported as Hexadella racovitzai this species was shown to be a species complex in 2012. Atlantic specimens belong to the new species Hexadella topsenti. (Reveillaud et al., 2012) Thin to thickly encrusting. Lateral expansion may be considerable, but thickness not exceeding 5 mm.

Colour: The colour is usually bright rose pink but can also be a pale greyish cream.

Consistency: Soft.

Surface: The surface has a characteristic reticulate structure with large oscules. It is smooth but demonstrating conules arranged in parallel ridges, similar to Aplysilla or Darwinella. The "skin" may be rather easily peeled off and has a characteristic reticulate appearance.

Apertures: Large raised oscules.

Internal characters

Skeleton: Absent. The skin is collagen-reinforced, and may act in some measure as external skeleton but otherwise the body is unsupported, with many channels and lacunae.

Spicules: Absent.

Habitat: On rocks, on pebbles, in deep water 9-85 m (Roscoff: 60 m). Steep shaded rockfaces and stable boulders, caves, usually below 25 m.

Distribution: Mediterranean, Roscoff, west coast of Ireland, Rathlin Island (Co Antrim), Canary Islands.

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

Identity: Recorded recently from off-shore exposed sites in Ireland, Rathlin Island and Pembrokeshire, Wales. It resembles Aplysilla or Darwinella, but is easily distinguished from them by the absence of any skeletal structures. Other such species are Chondrosia reniformis, but this is shiny-smooth and has a distinct cortex, Oscarella lobularis, but this has a lobulate surface, and Halisarca dujardini, but this has a smooth punctate surface. None of these species has conules nor are they rose-coloured.

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