Family CLATHRIIDAE (=MICROCIONIDAE)
Synonyms Isodictya beanii Bowerbank, 1866:334, Dictyoclathria beanii (Bwk., 1866) Burton, 1933:504, Myxilla involvens Schmidt, 1864:37. Antho inconstans Topsent, 1925 is considered to be a distinct species.
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.
Photographs BELUM: Mc1363. W. Blackstone, Skomer Island, south Wales. (B.E. Picton)
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.
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- 160μm in length. Ectosomal styles (a) are ca. 500μm. The accessory spicules are fine styles or subtylostyles (c) with microspined heads 330 x 4μm. Microscleres are palmate isochelae (d) (ca. 17-23μm), which may be rare, and toxa (e), which may be abundant.
Voucher BELUM : Mc1363. Skomer Island.
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.
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).
References Arndt, 1935, p.81. Lévi, 1960, pp.76-78.
Sources B.E. Picton, S.M. Stone. Editors D. Moss, B.E. Picton.
a
b
c d
Antho inconstans (Topsent, 1925 : 664).
Family CLATHRIIDAE (=MICROCIONIDAE) Synonyms Plocamia inconstans Topsent, 1925.
Form Thin sheet forming extensive patches on rock surfaces or on other sponges (e.g. Stelletta
grubii).
Photographs BELUM: Mc1826. S. of the Neck, Skomer Island, south Wales. (B.E. Picton)
Colour Orange-red. Smell None. Consistency Fairly tough sheet, which holds together well when scraped off. Surface Lumpy and irregular, with a slightly velvety appearance, similar to Microciona spinarcus.
Apertures Oscules inconspicuous, scattered, irregular in shape and size. Excurrent channels are generally conspicuous, converging on the oscules and forming irregular stars.
Contraction None to slight.
Skeleton An anisotropic reticulation, with a triangular or quadrangular mesh of megascleres (acanthostyles) of varying sizes, quasi- echinated by smooth megascleres at the internodes of the net. Longer smooth megascleres (styles) pierce the surface, but these are much shorter than the corresponding spicules in Antho involvens. Fine accessory ectosomal spicules are present.
Spicules Megascleres of the main skeleton are acanthostyles (b) and acanthostrongyles (c). The acanthostyles have a region of denser spination near the head and near the tip, and the smooth point itself is very short and abrupt. Typically ca. 135-155μm in length. Smooth ectosomal styles (a) ca. 200μm in length, slightly fusiform with a constriction above the head. The accessory spicules are fine subtylostyles (d) (sometimes styles) with microspined heads (this may not be visible with a light microscope). Microscleres are palmate isochelae (f) (ca. 17μm), which may be rare, and toxa (e), which may be abundant.
Voucher BELUM : Mc1349. Skomer Island.
Habitat Vertical or steeply inclined rock faces in both sheltered and exposed places. May be on other sponges such as
Stryphnus ponderosus and Stelletta grubii.
Distribution “South coast of England; France; Spain; Mediterranean etc.” Known recently from Lough Hyne, Co. Cork; W. Anglesey; Skomer; N. Cornwall; Jersey; Guernsey.
Identity Many Clathriids form red sheets, but the spicule complement is quite different from that of Microciona spp. The characters given here and for Antho involvens should distinguish these two species, which have often been synonymised in the past. Antho inconstans is easily confused with Plocamilla coriacea (Bwk 1874:228), which forms bumpy sheets and may also grow on other sponges, indeed the two species can be found growing alongside each other. Acanthostrongyles are the predominant megascleres of the main skeleton in Plocamilla, and the acanthostyles do not show the band of spines near the tip as in Antho inconstans, looking more like those in Antho involvens. Otherwise the spicule complement is similar for these three species (with slight size differences).
References Lévi, 1960, pp.78-80 as Antho involvens var. inconstans.
Sources B.E. Picton, S.M. Stone. Editors D. Moss, B.E. Picton.
a b c d
e f
SPECIES DESCRIPTIONS
Antho coriacea (Bowerbank, 1874: 228).
Family CLATHRIIDAE (= MICROCIONIDAE) Synonyms Plocamilla coriacea.
Form Moderately thin sheets, with a rounded rugose surfce, typically ca. 5mm thick.
Photographs BELUM: Mc1549. Goleen Cliff, Lough Hyne, Cork. (B.E. Picton)
Colour Bright orange-red or ochre yellow. Smell None?
Slime Not noticeable.
Consistency Fairly firm, holds together well when collected, but somewhat crumbly and easily torn.
Surface Fairly smooth in appearance, with moderate friction; tuberculate, uneven. N.B. Lévi (1960) describes it as “finely hispid”.
Apertures Oscules are inconspicuous. Contraction Slight - difficult to determine.
Skeleton The main skeletal feature is fairly regular, isotropic and dense reticulation of acanthostrongyles, with acanthostyles also present, the latter often in ‘upright’
positions. There are also a few larger styles, associated with ascending fibres and penetrating the surface (sometimes quasi-echinating the fibres). Slim subtylostyles form brushes at the surface. Very variable quantities of spongin reinforce the spicule fibres.
Spicules The megascleres include acanthostrongyles 80-100μm; acanthostyles of 110-190μm, the larger being very lightly spined at the head only; styles of ca. 300-400μm. The subtylostyles measure ca. 200-250 x 2-4μm. The microscleres are palmate isochelae, ca. 11-15μm and toxa which predominantly fall into two size groups: 30-60μm (relatively fine) and 130-180μm (more sturdy). The larger toxa may have spined points.
Voucher BELUM : Mc890. Saltee Islands, Wexford.
Habitat Vertical or steeply inclined rock faces from the shallow sublittoral downwards. Often found encrusting other sponges, such as Stelletta grubii and Stryphnus ponderosus. Most frequent in sites with moderate to strong tidal streams. Distribution Known recently from Ireland, Anglesey.
Identity In appearance this species is quite similar to many other of the troublesome ‘red crust’ Clathriids (especially
Antho involvens), but a bright orange red surface with a bumpy appearance is fairly recognisable. The spicule
complement, with a predominance of acanthostrongyles, is distinctive (see note for Antho involvens). Reference Lévi, 1960, p. 80.
Source D. Moss, B.E. Picton (S.M. Stone). Editors D. Moss, B.E. Picton. Draft 1 2/90 a b c d e f