Antho involvens (Schmidt, 1864)


Family : Microcionidae

Form: Thin sheet forming extensive patches on rock surfaces. In encrusting form it can be easily detached from the substrate. The literature claims "Can become branched - erect, sometimes stalked", but BEP considers this to refer to a separate species.

Colour: Watery orange to bright red.

Smell: None.

Consistency: Fairly tough sheet, which holds together well when scraped off.

Surface: Smooth, slightly hispid.

Apertures: Oscules conspicuous, spaced regularly across the surface, with slightly raised conical rims; circular and consistent in size. Ostia apparent on close examination. Excurrent channels are inconspicuous, not at the surface of the colony, but their ends are visible inside the oscules.

Contraction: None to slight.

Internal characters

Skeleton: An anisotropic reticulation, with a triangular or quadrangular mesh of megascleres (acanthostyles) (b) of varying sizes, many sparingly spined, often quasi-echinated by smooth megascleres at the internodes of the net. Long smooth megascleres (styles) (a) pierce the surface. Fine accessory ectosomal styles (c) are present.

Spicules: Megascleres of the main skeleton are acanthostyles (b), (never acanthostrongyles) entirely but often sparingly-spined; typically 145-160Ám in length. Ectosomal styles (a) are ca. 500Ám. The accessory spicules are fine styles or subtylostyles (c) with microspined heads 330 x 4Ám. Microscleres are palmate isochelae (d) (ca. 17-23Ám), which may be rare, and toxa (e), which may be abundant.

Habitat: Vertical or steeply inclined rock faces in both sheltered and exposed places.

Distribution: "South coast of England; France; Spain; Mediterranean etc." Known recently from Skomer; Rathlin Island. Confusion with Antho inconstans (q.v.) leaves previous records in doubt.

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

Identity: Many Clathriids form red sheets, but the spicule complement of Antho spp. is quite different from that of Microciona spp. Another British Antho sp. possibly to consider is A. dichotoma, a branching - erect, stalked species of unknown colour and almost identical spiculation. So far this has only been recorded from deeper water (82m +). Antho is also easily confused with Plocamilla coriacea (Bwk 1874:228) (q.v.), which forms bumpy sheets and may also grow on other sponges. Acanthostrongyles are the predominant megascleres of the main skeleton in Plocamilla, otherwise the spicule complement is similar for both species (with slight size differences).

Voucher: BELUM : Mc1363. Skomer Island.

Editors: D. Moss, B.E. Picton.

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