Antho dichotoma

(Esper, 1791-1794)

Species Overview

Antho dichotoma (Esper, 1791-1794) is a thinly and dichotomously branched sponge with a finely hispid surface. Colour is yellowish with reddish tinges. The species is common in deeper waters of NW Europe, especially in the Norwegian fjord area, and the Arctic, having its southern limits along the coasts of Ireland.

Taxonomic Description

Colour: Yellowish with a reddish tinge.
Shape, size, surface and consistency: 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. General consistency firm, barely compressible. No apparent oscules.
Spicules: (Antho dichotoma spics) 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.
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.
Ecology: In deep water, below 40 m, but generally below 100 m.
Distribution: From the Kola Peninsula in the North (Koltun, 1959) to the west coast of Ireland (Stephens, 1921).
Etymology: The name refers to the branching pattern.
Type specimen information: Type (Spongia dichotoma) probably lost.

Remarks

Related species of similar shape occur in the southern parts of the area: Antho involvens (Schmidt, 1864) may 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.
Source: Van Soest and Stone, 1986.