Antho dichotoma (Esper, 1794)


Family : Microcionidae

Form: Dichotomously branched sponge, up to 30 cm high. Branches thin, about 0.5 cm in diameter. Surface hispid through protruding spicules. Axially strengthened, thus difficult to break. No apparent oscules.

Colour: Pale beige, also reported as yellowish with a reddish tinge.

Consistency: General consistency firm, barely compressible.

Internal characters

Skeleton: An axial and extra-axial skeleton are developed: extra-axial skeleton consists of ectosomal subtylostyles in bouquets and long single styles erect on the axial reticulation and protruding far beyond the surface. The axial skeleton consists of spongin enforced longitudinal spicule tracts and interconnecting tracts, both consisting of short slightly acanthose or smooth styles, occasionally modified to strongyles.

Spicules: Megascleres : Ectosomal subtylostyles with microspined heads are 250-535 x 3-4 μm; structural megascleres are predominantly smooth, or lightly spined choanosomal styles, 150-210 x 9.5-14 μm making up the choanosomal reticulation; ectosomal protruding styles are 350-3000 x 12-18 μm. Microscleres : Palmate isochelas of 12-28 μm and toxas in two size categories: 190-305 μm with acanthose apices, and 35-95 μm.

Habitat: In deep water, below 40 m, but generally below 100 m. Other conspicuous sponges in the same habitat include Phakellia ventilabrum and Quasillina brevis.

Distribution: From the Kola Peninsula in the North (Koltun, 1959) to the west coast of Ireland (Stephens, 1921).

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

Identity: Related species of similar shape occur in the southern parts of the area: Antho involvens (Schmidt, 1864) is reported to have encrusting as well as thinly branching forms; the ill-known Antho erecta (Ferrer-Hernandez, 1922) has a bladed-branching form dissimilar to A . dichotoma. Both differ from A . dichotoma in having the choanosomal styles/strongyles entirely acanthose.

Voucher: BELUM:Mc3678, Egersund, Norway.

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