(Montagu, 1818)
Species Overview
Acervochalina limbata (Montagu, 1818) forms small brown spiny cushions, very compressible and spongy. Oscules are at the summit of small chimneys or flush. It is a common inhabitant of the brown algae communities in intertidal and subtidal habitats. It occurs over most of Western Europe.
Taxonomic Description
Colour: Brown.
Shape, size, surface and consistency: Cushion-shaped or lobate, with a few, rather large, flush oscules or oscular chimneys. Diameter of oscules 4-10 mm. Size of specimens up to 2 cm high and 5 cm in diameter, but often much smaller. Surface strongly hispid. Consistency resilient, compressible, very spongy.
Spicules: Small, thin oxeas of variable size, usually: 55-90 x 0.5-1.5 µm. Centrotylote modifications occur occasionally.
Skeleton: Ectosomal skeleton: absent. Choanosomal skeleton (Acervochalina limbata skdrw): consists of an irregular reticulation of spongin fibres of varying thickness, cored by 1-5 oxeas. Usually the primary fibres are thicker and cored by more spicules than the secondary fibres. Spongin: variable, but generally abundant, forming the main part of the skeleton.
Reproduction: Larvae are pink and have bare posterior and anterior poles, size 150-500 µm (Meeuwis, 1939; Wapstra and Van Soest, 1987).
Ecology: In the intertidal and shallow subtidal area, growing on Fucus etc.
Distribution: Norway, Denmark, west coast Sweden, British Isles, France, Spain, Portugal, Mediterranean.
Etymology: Limbatus (Latin) = fringed, referring to the spined surface which give the oscules a fringed aspect.
Type specimen information: Holotype not extant (?). Earliest described material available is several specimens of the Johnston collection in BMNH, no.'s 1847:9:7:88-89, 91, labeled Spongia limbata .
Remarks
Acervochalina limbata is characterized by its resilient, spongy consistency. It differs from the other tubular Acervochalina species of the study area (A . loosanoffi) by its much firmer consistency, by the higher development of spongin, and by the absence of gemmulae. These are characteristically present in A . loosanoffi . Remarkable is the variation in the size of the oxeas and the amount of spongin (cf. also Van Soest, 1976).
Source: De Weerdt, 1986