Family CLATHRIIDAE (=MICROCIONIDAE) Synonyms Ophlitaspongia papilla Bowerbank, 1866:378.
Form Thin sheets, usually 2 - 3mm thick, but can develop into cushions of uniform thickness up to 10mm thick. Diameter of the animal may be up to 10cm.
Photographs The Rapids, Lough Hyne, Cork. (B.E. Picton)
Colour Deep orange - red. The pigment squeezes out readily.
Smell “Not strong” - “none” (?).
Consistency Moderately firm and elastic. “Compressible, resilient. Breaks somewhat in the manner of a soft biscuit.”
Surface Very finely granular, “even, hispid”, “minutely wrinkled”. The surface has a smooth dense appearance which is quite distinctive.
Apertures The oscules are conspicuous and evenly distributed in a regular fashion between 5 and 10mm apart over the surface. Neat, round and mostly flush with the surface, but the margins can be raised slightly above the surface. “Occasionally sub-fistular.”
Contraction None.
Skeleton Very characteristic. In cross-section a ladder-like skeleton of spongin can be seen, which forms an anisotropic reticulation of well developed fibres. The primary ascending fibres are semi-cored by plumosely arranged megascleres, which often quasi-echinate the fibres. The secondary connecting fibres usually do not contain spicules. Accessory spicules are usually interstitial, rather than at the surface.
Spicules The principal megascleres of the main skeleton are short fat styles or subtylostyles (a) 110-(117)-130μm. The accessory spicules are thin subtylostyles (b) 105-(118)-130μm. The microscleres are toxa (c) with smooth tips 50-(55)-60μm. Chelae are absent.
Voucher BELUM : Mc588. Rutland Harbour, Donegal.
Habitat On rock, commonly under boulders on the lower shore and also in the shallow sublittoral (to 5m CD). “On clean rock, shells, Fucus,” and
Laminaria stipes in areas of strong water movement (either tidal or
wave action).
Distribution “British Isles; France and Spain.” A common shore species with recent records from south-west England, western Ireland, Strangford Lough and Tiree. Fry (1971) did research on this species from the Menai Straits and Anglesey.
Identity Superficially Ophlitaspongia seriata could be confused with several other species. However the spiculation is distinctive and the form, colour and habitat make it readily identifiable. It could be confused with Amphilectus
fucorum (q.v.) but when alive the strong smell of Amphilectus can be used as an initial indication; Amphilectus
has a much softer consistency. It could also be confused with Microciona atrasanguinea (q.v., a shallow sublittoral species which also forms thin sheets), but whereas Ophlitaspongia can be peeled off the rock, Microciona usually crumbles and tears and is much thinner. The spiculation is also very different. References Arndt, 1935, p.82. Bowerbank, 1866, p.377; 1874, p.167. Fry, 1971, pp.158-178. Lévi, 1960, p.64. Simpson, 1968, pp.37, 89-119.
Sources B.E. Picton, S.M. Stone. Editors R. Earll, D. Moss, B.E. Picton.
a b
c
SPECIES DESCRIPTIONS
Microciona atrasanguinea Bowerbank, 1862:824.
Family CLATHRIIDAE (=MICROCIONIDAE)
Synonyms Plumohalichondria atrasanguinea (Bowerbank, 1862:824) Hanitsch, 1890:207
Form Thin sheets covering extensive areas, typically 3mm thick by up to 30cm diameter. In the literature it has been reported as a cushion, but this may be the result of the sponge growing over a saddle oyster (BEP). Typically looks like a patch of red paint.
Photographs BELUM: Mc140. Lee’s Wreck, Strangford Lough, Down. (B.E. Picton)
Colour Bright red, scarlet or blood red. The blood-red sublittoral form is described here, and may be a distinct species from the scarlet one which seems to occur both in the littoral and sublittoral.
Smell None.
Consistency Difficult to determine because of thinness of sheet but fairly soft; difficult to scrape off - it crumbles and tears.
Surface With little structure - conforms closely to the underlying substrate. Excurrent channels are clearly visible as dark branching lines converging on the oscules. Slightly velvety appearance; minutely porous. “Tuberculate, hispid; often creviced” according to Lévi (1960).
Apertures Oscules have slightly raised transparent rims, apparent mainly because of converging excurrent channels. These oscules are “numerous and regularly spaced over the surface”.
Contraction Difficult to determine.
Skeleton In the littoral form (juvenile) the skeleton is usually ‘Hymedesmoid’, with both the principal spicules of the main skeleton (usually styles) and also the auxiliary spicules (acanthostyles) standing up from a basal sheet of spongin, the bases of the spicules being implanted in the spongin and the points directed towards the surface. Slender accessory spicules (subtylostyles) are scattered throughout.
In thicker sublittoral specimens (adult form) the skeleton becomes ‘plumose’. The main skeleton then consists of plumose columns of spicules incorporating spongin ‘raised’ from the basal layer of the juvenile form. These are in turn echinated by smaller spicules (acanthostyles). Slender ectosomal spicules are present.
Spicules Principal spicules of the main skeleton are subtylostyles (a) (rarely sparingly spined at the base) which measure 220-(250)-280μm long x 10μm thick and 110-(130)-145μm; (note however that Lévi (1960) gives a size range of 110-375μm. Auxiliary megascleres are entirely-spined acanthostyles (b), 80-(90)-135μm. Slender accessory subtylostyles (c) measure 225-(260)-355μm and have microspined heads. The microscleres comprise palmate isochelae (d) 8.5-12μm, and smooth tipped toxa (e), which may be numerous, 100-125μm and 18-40μm.
Voucher BELUM : Mc821. Strangford Lough, Down.
Habitat Vertical surfaces of rock or wrecks. Boulders in brackish conditions. Encrusting pebbles in areas of strong current (Menai Straits) in the Littoral zone.
Distribution “Atlantic coasts of Europe (from Shetlands southwards), Mediterranean etc.” Known recently from Strangford Lough; Rathlin Island; Menai Straits; Daucleddau, Milford Haven. Littoral or shallow sublittoral. a b d c e
Identity Microciona species and other Clathriids often form thin reddish sheets. The dendritic branching of the
excurrent channels of this species may be characteristic but the spicules should always be checked for a positive identification. Superficially it may be confused with Ophlitaspongia seriata (q.v.), but note the regular arrangement of oscules in the latter species which is not so apparent in M. atrasanguinea.
References Arndt, 1935, p.78. Lévi, 1960, p.72.
Sources B.E. Picton, S.M. Stone, (D. Moss). Editors D. Moss, B.E. Picton.