Mycale (Paresperella) seychellensis, Van & Aryasari & De, 2021

Van, Rob W. M., Aryasari, Ratih & De, Nicole J., 2021, Mycale species of the tropical Indo-West Pacific (Porifera, Demospongiae, Poecilosclerida), Zootaxa 4912 (1), pp. 1-212 : 172-174

Mycale (Paresperella) seychellensis sp.nov.

Figs 112 a–g

? Paresperella spec. Dendy, 1922: 58.

? Mycale sp. 2 Vacelet & Vasseur 1971: 89, fig. 39.

Material examined. ZMA Por. 12658, Seychelles, Amirantes , Desroches Atoll, SW rim, outer reef slope, 5.7167°S 53.6167°E, depth 5–30 m , SCUBA, coll. M.J. de Kluijver, Netherlands Indian Ocean Expedition stat. 774, field nr. IOP-E 774/04b, 30 December 1992 (yellowish) .

Description. Tiny specimen encrusting on calcareous sponge ( Borojevia tubulata Van Soest & De Voogd, 2018 ). Life color noted as yellowish, pale beige in preservation. Size 1–2 mm 3. After two thick sections were made, the left over material was barely enough for further subsampling for SEM and light microscopy.

Skeleton ( Figs 112 a–b). Feebly developed due to being a small specimen. Plumose choanosomal tracts of 60–80 µm diameter subdivide into thinner tracts below the surface. The ectosomal skeleton is an irregular aegogropila-type tangential arrangement of intercrossing spicule tracts of about 20 µm diameter (3–4 spicules in cross section) and single megascleres, forming meshes of about 200 µm in widest expansion. Rosettes of anisochelae I of 45–60 µm diameter and spined sigmas are scattered in the ectosomal meshes.

Spicules ( Figs 112 c–g). Megascleres, two categories of anisochelae, sigmas, toxas.

Megascleres ( Fig. 112c,c 1 ) are anisotylote and anisostrongylote forms, with slightly unequal swollen rounded ends on both sides, straight or curved, sometimes slightly sinuous, 401– 418.9 –434 x 5– 5.9 – 7 µm.

Anisochelae I ( Figs 112d ), well-developed, with curved shaft, overall shape similar to those of M. (P.) sceptroides sp.nov., cf. above, but smaller, 23– 26.8 – 31 µm.

Anisochelae II ( Fig. 112e ), similar to anisochelae I, but less well-developed and distinctly smaller, 15– 15.5 – 17 µm.

Sigmas I ( Figs 112f,f 1 ), approximately symmetrical, thickness about 3 µm, with curvature of both endings provided with a series of flattened spines, clearly larger in size than above treated Mycale (Paresperella) species, 105– 124.8 – 138 µm.

Toxas ( Fig. 112g ), in dragmas or occasionally single, similar in shape to those of M. (P.) sceptroides sp.nov., 15– 29.8 – 36 µm.

Distribution and ecology. Seychelles, on reefs, down to 30 m.

Remarks. The present material is close to M. (P.) sceptroides sp.nov. but differs clearly in (1) shape of the megascleres which lack the polyaxone ending, (2) the size of the anisochelae I (37–57 µm vs 23–31 µm), and (3) size of the serrated sigmas (63–87 vs 105–138 µm). Less important differences are the more robust choanosomal tracts and the lack of toxodragmas in M. (P.) sceptroides sp.nov.

A further closely related species appears to be M. (P.) serratohamata ( Carter, 1880) , likewise apparently only known from tiny specimens, which has similar spiculation including toxas. A distinct difference with the new species is that the serratohamata has commonplace mycalostyles with pointed endings and much smaller size (175 x 6 µm); toxas (in dragmas like our specimen) are 50 µm.

East Pacific Mycale (Paresperella) psila ( De Laubenfels, 1930) as redescribed recently by Carballo & Cruz-Barraza (2010) differs clearly from the new species in having a second smaller category of sigmas, and its sigmas I and toxas are distinctly larger (130–188 µm and 42–63 respectively).

It is possible that Dendy’s (1922: 58) record of a Paresperella spec. from Salomon Island (Chagos, British Indian Ocean Territory) is a member of the new species, but only a large serrated sigma is known for it. Similarly, Vacelet & Vasseur’s (1971) record of Mycale sp. 2 appears a potential member of the new species, with the main difference being bundled raphides of 280–320 µm, lacking in our tiny specimen.

Additional species of Mycale (Paresperella) from the region

Figures

FIGURE 1. A. Numbers of available specimens for the present study from the collections of the Naturalis Biodiversity Center distributed over Indo-West Pacific Marine Ecoregions (MEOWS, cf. Spalding et al. 2007). B. Ditto for type specimens and additional specimens from other institutions consulted for this study.

FIGURE 112. Mycale (Paresperella) seychellensis sp.nov., holotype ZMA Por. 12658, from Amirantes, Seychelles, a–b, light microscopic images of the skeleton, a, ectosomal skeleton, b, detail showing megascleres, rosettes of anisochelae I, and various microscleres (including toxodragmas), c–g, SEM images of spicules, c, anisotylote megasclere, c1, details of the megasclere, d, anisochelae I in front view (left) and side view (right), e, anisochela II, f, serrated sigma, f1, detail of serrated sigma, g, toxa.