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(Esper, 1794)

Species Overview

Amphilectus fucorum (Esper, 1794), also known as Esperiopsis fucorum, is a polymorphic orange encrusting or repent ramose soft sponge occurring in the shallow sublittoral, typically overgrowing Laminaria holdfasts or sessile invertebrates.

Taxonomic Description

Colour: An intense reddish orange. The pigment squeezes out easily between thumb and forefinger. It turns colourless in alcohol. The sponge may be colourless in deeper water.
Shape, size, surface and consistency: Extremely polymorphic (amphilectus_fucorum_mcs1.jpg) and fast-growing, changing shape in a few weeks. Encrusting (amphilectus_fucorum_mcs2.jpg) as thin sheets or cushions (amphilectus_fucorum_mcs4.jpg), massive-lobose (with or without 'tassels'amphilectus_fucorum_mcs5.jpg), or branched (amphilectus_fucorum_mcs3.jpg). It can also occur in hollow 'amphora' shaped forms in sheltered conditions. For more information on relationships of form and habitat cf. Stone et al., 1987. Size may range from a few cm2 to several dm2, up to 15 cm high. The oscules may be only slightly raised from the surface, or be characteristically at the top of volcano-like growths, and may have 'tassel' growths originating near the margin of the oscules. The oscules do not contract. They are inconspicuous in encrusting forms, and large or crateriform in massive forms; they are often arranged in linear series in the branching forms. Surface even, minutely hispid, moderate friction, fairly open in appearance. The subectosomal tissue is peppered with inhalant pore channels, which are covered with a thin, transparent layer. This is apparent in the field. It has a characteristic and unpleasant strong smell—not dissimilar to that of Halichondria (Halichondria) panicea. Slime not produced. Consistency soft and easily torn. Slight contraction.
Spicules: (amphilectus_fucorum_spics.jpg) Megascleres: Smooth, usually curved, styles, size variable: up to 170-500 x 10-19 µm, more often 150-200 x 3-5 µm.
Microscleres: Small palmate isochelae, which may be rare: 14-28 µm.
Skeleton: Plumoreticulate. The main skeleton is an isodictyal to sub-isodictyal reticulation of multispicular fibres, reinforced with variable amounts of spongin (depending on the age of the sponge). There are no echinating spicules, nor any special ectosomal skeleton.
Reproduction: August (Lévi, 1956)
Ecology: A wide range, from moderately exposed sites to those experiencing greater or lesser extremes of exposure or shelter. It may be found in strong tidal rapids, e.g. Menai Straits (Wales) and Strangford narrows (N Ireland); on rock and under stones; amongst hydroids (it will grow up Tubularia stems) and has even been found on ascidian tests. It is often found growing on/in Laminaria holdfasts on the lower shore and shallow sublittoral. The 'amphora' form grows on shells in sheltered places. An infralittoral species, seldom (never?) found in the circalittoral zone. Associated species: amphipods and nematodes. Down to 108 m.
Distribution: Atlantic coasts of Europe from Norway and the Faroes to the Mediterranean (latter record is by Uriz, 1983).
Etymology: The name refers to the frequent occurrence among Fucus weeds.
Type specimen information: The type (Spongia fucorum) is probably lost. MCS voucher: BELUM Mc175, Strangford Lough, N Ireland.

Remarks

The shape of this sponge is very variable and is in many ways almost as polymorphic as Halichondria panicea; like H. panicea it also occurs in a wide variety of situations. It is a very common species in the shallow sublittoral, especially in areas of increased water movement, e.g. tidal narrows. The smell, nature of the tassel form, the oscules, colour and surface texture in combination are useful in helping recognition of this sponge, whilst alive or freshly collected.
There are a large number of Bowerbank synonyms (Isodictya fucorum) to be checked (Isodictya dubia-imitata) which may result in a 'splitting' of the entity A. fucorum as now understood (Isodictya edwardii).
Amphilectus lobatus may be superficially very similar to A. fucorum; the spiculation of the two species is almost identical. However, A. lobatus has a more regular skeleton of ascending bundles of styles with single connecting styles. The chelae of A. lobatus are anisochelae with only slightly disparate ends. A. lobatus is cream coloured when alive.
Source: B.E. Picton, S.M. Stone, G. Ackers, D. Moss. in Ackers et al., 1985; van Soest & Hajdu, 2002.

Amphilectus fucorum