Acervochalina limbata (Montagu, 1818)


Family : Chalinidae

Form: Cushions, 1 to 3cm across.

Colour: Brown.

Consistency: Soft, elastic and tough; "lightweight" and spongy.

Surface: Even, regularly and finely conulate.

Apertures: Oscules are conspicuous, typically up to 3 in number, 1-3mm diameter. Normally flush with the surface, but the longer oscules may have a slightly elevated rim.

Contraction: None.

Internal characters

Skeleton: The skeleton consists of conspicuous fibres of spongin in an irregular reticulation. The fibres have a large width range, between ca. 5-120Ám, and are sparsely to densely cored by oxea, some of which may be scattered outside the fibres.

Spicules: The megascleres are oxea, 55-90Ám by 0.5-1.5Ám. In some specimens centrotylote swellings occur. They are much smaller than the oxea in most Haliclona species. There are no microscleres.

Habitat: Found in the intertidal growing on brown seaweeds such as Fucus and Cystoseira and beneath boulders and stones.

Distribution: Probably occurs all around the British Isles, but is not well known. Known recently from Mull, Anglesey and Lough Ine.

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

Identity: The other two conulate species with which this species could possibly be confused are Dysidea fragilis and Ulosa digitata. Both these species tend to be larger, not confined to the shore, and possess coarser conules (the conules of A. limbata are very short and regular, giving the surface an almost hispid appearance). Both have skeletal fibres, but Dysidea fragilis does not possess spicules, and the fibres of Ulosa digitata are cored by styles, not oxea. With a little experience it should be possible to identify A. limbata in the field.

Voucher: BELUM : Mc375. Skye, Scotland.

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

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