Ectyodoryx minuta, Calcinai & Pansini, 2000

Calcinai, Barbara & Pansini, Maurizio, 2000, Four new demosponge species from Terra Nova Bay (Ross Sea, Antarctica), Zoosystema 22 (2), pp. 369-381 : 375-376

Ectyodoryx minuta n. sp.

( Figs 4 ; 5)

MATERIAL EXAMINED. — Holotype: POR23 ( MNA No 2); paratype: stn MM31 , 12.I.1990, rock, 197 m, POR23 ( MSNG).

ETYMOLOGY. — The small size of the megascleres compared with congeneric Antarctic species suggested the specific name.

TYPE LOCALITY. — Terra Nova Bay, 74°42.2’S, 164°10.9’E.

DESCRIPTION

The only specimen collected is 3.5 cm by 2 cm and overgrowing serpulid tubes ( Fig. 4A ). The overall appearance of the sponge is bushy amorphous but, on a closer examination, the surface pattern is drawn by the rounded extremities of the branches ( Fig. 4B ). The alcohol-preserved specimen is very fragile and the holotype is broken into fragments.

Skeleton

Most of the ectosome has been torn off probably during sampling by the dredge, but in a few positions a thin (50-150 µm) but dense layer of microscleres and paratangential anisotornotes is still detectable; the megascleres never form brushes ( Fig. 4C ). Choanosomal acanthostyles protrude through this layer rendering the sponge surface bristly. The choanosomal skeleton consists of indistinctly square-meshed reticulation and tracts formed by single or few (2-5) almost smooth acanthostyles ( Fig. 4D ). These tracts are sparingly echinated by smaller more spiny acanthostyles. Abundant microscleres are included into the reticulation. Spongin is scarce.

Spicules

Large acanthostyles, gently curved, with roundish, weakly pronounced head ( Figs 4G, J ; 5A). Spines are small, few and scattered, generally concentrated over the head. They measure 219- 260 (238.5) × 7-10 (8.6) µm.

Small, echinating acanthostyles, straight or gently curved, more fusiform than the larger acanthostyles and with spines uniformly distributed over the head and shaft ( Figs 4E ; 5B). They measure 102-132 (115) × 5-10 (7) µm. The size of the two categories of acanthostyles is overlapping, but they may be distinguished by their shape.

Anisotornotes, slender and straight, having one slightly swollen extremity and the other one tapering into a point ( Figs 4F, I ; 5C). They have a stylote appearance and measure 183-199 (188) × 2.6-5 µm.

Two categories of arcuate isochelae: slender and rather straight 14-18 (15.7) × 1-1.3 µm ( Fig. 5E); and thick and more arcuate 20-30 (25) × 2.5- 4 µm ( Fig. 5D). The shape of the two forms is similar under the optical microscope but very different when viewed by SEM ( Fig. 4K, L ).

Sigmas: “C” – and “S” – shaped, thin and very abundant ( Figs 4H ; 5F); 20-56 (27) × 1-2 µm.

REMARKS

The new species is assigned to the genus Ectyodoryx Lundbeck, 1909 because of its reticulated choanosome, ectosome with anisotornotes(though not forming brushes),absence of acanthostyles,and presence of arcuate isochelae and sigmas as microscleres (see Bergquist & Fromont 1988). Three other species, Ectyodoryx antarctica (Hentschel, 1914) , E. nobilis (Ridley & Dendy, 1886) and E. ramilobosa (Topsent, 1916) , belong to the fauna of Terra Nova Bay (Pansini et al. 1994). Two more species are recorded from the Antarctic, E. anacantha Hentschel, 1914 and E. plumosa Hentschel, 1914 , although Koltun (1976) considers them very close.Both differ from the new species by the external morphology and by the shape and size of the spicules. Ectyodoryx crelloides BrØndsted, 1924 from New Zealand has the branching habit, reduced choanosomal echination, and the small spicule size of E. minuta n.sp., but the spicule shape is completely different. Ectyodoryx minuta n. sp. is distinguished from all other species of the genus by the small size of the megascleres, the peculiar shape of the anisotornotes, and the presence of two categories of isochelae.

Family NIPHATIDAE Van Soest, 1980

Figures

FIG. 4. — Ectyodoryx minuta n. sp.; A, holotype; B, detail of the sponge surface; C, ectosome; D, choanosomal skeleton; E, head of an echinating acanthostyle; F, I, extremities of anisotornotes; G, J, acanthostyles forming the choanosomal reticulation; H, group of sigmas; K, slender isochela; L, thick and arcuate isochela. Scale bars: A, 1 cm; B, 3 mm; C, 600 µm; D, 160 µm; E, H, K, L, 10 µm; F, I, 5 µm; G, 100 µm; J, 40 µm.