Raspailia (Raspailia) radiosa (Bowerbank, 1866) is a branching-erect sponge, with stiff, dichotomously dividing branches with hispid surface. It is indistinguishable from Raspailia (R.) hispida in appearance but differs in spicules (microscopic examination). It is an ill-known species, recorded only twice from the British Isles; it needs redescription from fresh specimens.
Colour: Nut-brown in the dried state.
Shape, size, surface and consistency: Branching-erect, with hispid, compressed, branches, dichotomously dividing in one plane. Size up to 7 cm high, 8 cm wide, branches 2-4 mm in diameter. Surface strongly hispid. Oscules tiny, distributed over the branches. Consistency hard (dry state).
Spicules: (Raspailia radiosa spics) Styles, somewhat flexuous: up to 1400 x 10-12 µm; acanthostyles, entirely spined: ca. 100 x 5 µm; oxeas, in two size classes: 1000-1100 x 5-10 µm, and 800 x 2 µm.
Skeleton: Extra-axial: the usual Raspailid brushes of thin oxeas surrounding a single large style; axial: a mass of styles and long flexuous oxeas, echinated by acanthostyles.
Ecology: No data.
Distribution: Channel Islands, Plymouth.
Etymology: The name refers to the ectosomal skeleton consisting of circles of anisoxeas surrounding a single large style.
Type specimen information: BMNH: 1910.1.1.2338 and 9 (slides) (Bk 400). Vazon Bay, Guernsey. Norman Collection.
It is tempting to consider the few specimens recorded by Bowerbank (1866) and Burton (1957) as deviating specimens of Raspailia (R.) hispida. The large oxeas exceeding those of R. (R.) hispida clearly in length and position (the thicker ones are found in the axial skeleton) prevent such synonymization. Unfortunately, Burton (1957) deemed it unnecessary to substantiate his Plymouth record of this species by a description. For the time being it is considered a separate species.
Source: Bowerbank (1866).