Desmanthus meandroides, Van Soest & Hajdu, 2000

Van Soest, Rob W. M. & Hajdu, Eduardo, 2000, New species of Desmanthus (Porifera, Demospongiae) with a discussion of its ordinal relationships, Zoosystema 22 (2), pp. 299-312 : 302-304

Desmanthus meandroides n. sp.

( Fig. 1 A-E)

HOLOTYPE. — Celada. Baía de Castelhanos, Ilha de São Sebastião, São Paulo State, 23 °50.3’S, 45°14.6’W, c. 7 m, 25.I.1996, coll. E. Hajdu and G. Muricy (MNRJ 341).

PARATYPES. — Saco da Serraria. Ilha de São Sebastião, São Paulo State, 23 °48.5’S, 45°14.5’W, 13 m, 11.I.1996, coll. E. Hajdu (MNRJ 109, 114 and 119).

Saco do Frade. Ilha de São Sebastião, São Paulo State, 23°55.3’S, 45°27.3’, 24 m, 16.I.1996, coll. E. Hajdu (WDZUSP 148, 151 and 166), Schizotype from holotype ZMA POR13400.

ETYMOLOGY. — Named after the meandroid system of superficial canals.

DISTRIBUTION. — South East Brazil, encrusting on rocks, barnacles and polychaete tubes, in 7-24 m depth.

DESCRIPTION

Thinly encrusting specimens covering rocks and various calcareous substrates (e.g. polychaete tubes, barnacles, gastropods). The area covered may be larger than 200 cm 2. Live colour is an intense orange. Discrete subectosomal aquiferous channels clearly visible resulting in a very characteristic meandriform surface ( Fig. 1A ).

Skeleton

The surface is pierced by the numerous curved styles which stand erect on the substrate, heads in between the desmas II. No specialized ectosomal skeleton is apparent. Choanosomal skeleton composed of a basal layer of rhabdome-free desmas I forming an irregular interlocked mass with moderate zygosis. On top of this basal layer a further layer of desmas II is present ( Fig. 1B ). These desmas have their cladomes facing down, and the prominent rhabdomes pointing outwards to, but not reaching the sponge surface. The rhabdomes of the desmas II alternate with single erect styles.

Spicules

Smooth desmas I ( Fig. 1D ), relatively more branched and thinner than desmas II, dimensions: 155-291 × 5-6 µm. Smooth, more robust desmas II ( Fig. 1C ), with cladomes disposed in a concave manner, irregularly tuberculate, of similar dimensions, but with thicker branches, dimensions: 155-267 × 8-17 µm. Rhabdomes often slightly curved, most are smooth, but sometimes end in a crown of conules, dimensions: 49- 204 × 10-30 µm. Smooth rather robust styles ( Fig. 1E ), slightly thicker at the base, with sharp point, most often slightly bent in the basal quarter. Very variable in size, but without distinct categories, dimensions: 126-834 × 8-10 µm.

REMARKS

On account of the prominent rhabds, the new species is probably closest to Desmanthus rhabdophorus (Hentschel, 1912 as Lophacanthus ) from eastern Indonesia and D. levii n. sp. from the East Pacific (cf. below). Differences are the size of desmas I (smaller in both other species, dimensions: respectively 150-160 µm and 87-112 µm) and the length of the rhabdome of desmas II (184- 256 µm in L. rhabdophorus exceeding that of D. meandroides n. sp., and 78-116 µm in D. levii n. sp., clearly smaller on average than that of D. meandroides n. sp.).

This species is common in the São Sebastião area, SP, SE Brazil, where it occurs on semi-vertical walls exposed to good illumination.

Figures

FIG. 1. — A-E, Desmanthus meandroides n. sp.; A, habit of holotype, MNRJ 341, photographed in situ; B, from holotype, partly cleaned section of desma II skeleton showing forest of outward-pointing rhabdomes; C, from holotype, desma II showing prominent rhabdome; D, from holotype, desma I; E, from holotype, style; F-I, Desmanthus levii n. sp.; F, from holotype ZMA 13398, uncleaned section shown sideways. Arrows indicate desma II rhabdomes protruding into the surface membrane among the styles; G, from holotype, desma II showing prominent rhabdome and concave cladome; H, from holotype, desma I; I, from holotype, style (scale bar: bar shared with Fig. 1E = 100 µm). Scale bars: A, 1 cm; B-I, 100 µm.