Mycale (Mycale) asigmata, 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 : 107-109

Mycale (Mycale) asigmata sp.nov.

Figs 68 a–f, 69a–g

Material examined. Holotype ZMA Por. 09321, Indonesia, Nusa Tenggara, NE coast of Sumba , E of Melolo, 9.8917°S 120.7117°E, depth 75–90 m, bottom calcareous stones, rectangular dredge, coll. R. W.M. van Soest, Indonesian-Dutch Snellius II Expedition stat. 051, field nr. 051/ VI / Dreg /05, 13 September 1984 (light brown).

Paratype ZMA Por. 09140, same data as holotype (light brown) .

Description ( Fig. 68a ). In life, light brown massive sponges, with irregular surface covered by a detachable ectosomal membrane. Preserved material shredded and fragmented, together forming a crumbly fibrous mass. Estimated size 15 x 10 cm, thickness up to 3 cm. Color in alcohol red-brown, darker than in situ . Consistency soft and compressible, easily damaged.

Skeleton ( Figs 68 b–f). Choanosomal tracts arranged plumosely, with strong long spicule tracts, 90–135 µm diameter (8–10 spicules in cross section), distances between them 200–500 µm, few interconnecting tracts. Near the surface the tracts subdivide and fan out to carry the ectosomal skeleton ( Fig. 68b ). This resembles that of M. (M.) crassissima , in being comparatively open, with tangential megascleres arranged in ill-defined short bundles, next to individual spicules. No clear rosettes of anisochelae, but on the subsurface choanosomal tracts the anisochelae are arranged in loose clusters or ‘pseudorosettes’ ( Figs 68 c–d). In the open spaces between the ectosomal megascleres numerous trichodragmas ( Fig. 68 e–f) of various sizes are occurring in dense aggregations.

Spicules ( Figs 69 a–g). Mycalostyles, three categories of anisochelae, three categories of trichodragmas (no sigmas).

Mycalostyles ( Fig. 69a,a 1 ), comparatively robust, fusiform, with elongated heads and faintly developed subterminal constriction, 362– 408.6 –438 x 9– 12.8 – 15 µm.

Anisochelae I ( Fig. 69b ), common, compact, with free part of the shaft 25% of spicule length, with upper alae broadly extended and median alae oval and slightly shorter than the lateral alae, lower alae characteristically broadly extended with rounded upper rim, 46– 69.3 – 81 µm.

Anisochelae II ( Fig. 69c ), not common, overall shape elongated, free part of the shaft variable, 25–35% of spicule length, upper median alae slightly extended, as long as the lateral alae, 22– 25.8 – 33 µm.

Anisochelae III ( Figs 69d ), not common, shape largely similar to anisochelae II, 15– 17.5 – 19 µm. Trichodragmas I ( Fig. 69e ), fusiform, 32– 42.6 –57 x 6– 6.8 – 10 µm.

Trichodragmas II ( Fig. 69f ), rectangular to oval, 12– 15.2 –18 x 4– 6.6 – 9 µm

Trichodragmas III ( Fig. 69g ), rectangular to oval, 4– 5.9 –8 x 1–1.5 µm

Distribution and ecology. Dredged near Sumba, Indonesia, at greater depth (75–90 m).

Etymology. The name refers to the absence of sigmas.

Remarks. The new species stands out among Mycale (Mycale) species reported from the study area by the absence of sigmas combined with the possession of three size categories of trichodragmas. A further feature is the characteristic compact shape of anisochelae I with its broadly extended median alae, especially the lower median alae. Apart from the absence of sigmas, there is some resemblance to M. (M.) crassissima (cf. below) in spicule complement (anisochelae in three categories, trichodragmas), but the anisochelae III of that species possess a distinct spur, lacking in the present material. M. (M.) grandis s.l. also have a spurred anisochelae III, and in addition have peculiar large anisochelae I unlike the present species.

The only other species of Mycale (Mycale) lacking sigmas and possessing trichodragmas is deep water (300 m) Mycale (Mycale) myriasclera Lévi & Lévi, 1983 . This has only two categories of anisochelae, and anisochelae I have the curved shape and short upper alae of M. (M.) dendyi -like anisochelae I, quite unlike those of the present new species. The length of the ‘milliards’ of raphides is given as 120 µm, well in excess of those of the present new species. Also the mycalostyles of M. (M.) myriasclera are distinctly longer, 750–900 m, twice the length of those cited above. Mycale (Mycale) incurvata Lévi, 1993 , also from deep water off New Caledonia, is again similar to M. (M.) asigmata sp.nov. and M. (M.) myriasclera , but this not only lacks sigmas but also trichodragmas. M. (M.) incurvata is very close to Mycale (Mycale) trichela Levi, 1963 from the Atlantic side of South Africa (so outside our target region), in having three size categories of anisochelae, lacking both sigmas and trichodragmas or raphides, but the shape and the distinctly larger mycalostyles (up to 725 x 20 µm of M. (M.) trichela , only 400–590 µm in M. (M.) incurvata ), make them distinct.

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 68. Mycale (Mycale) asigmata sp.nov., holotype ZMA Por. 09321, from Indonesia, a, preserved habitus (scale bar = 1 cm), b–f, light microscopic images of the skeleton, b, ectosomal skeleton, c, small cluster (pseudorosette) of anisochelae I, d, a string of pseudorosettes along a subectosomal skeletal tract, e, a cluster of trichodragma I, f. clusters of tiny trichodragmas II (arrows).

FIGURE 69. Mycale (Mycale) asigmata sp.nov., holotype ZMA Por. 09321, from Indonesia, a–g, SEM images of spicules, a, mycalostyle, a1, details of mycalostyle, b, anisochela I with characteristic broadly extended upper and lower alae, c, anisochela II in front view, d, anisochelae III in front and side view, e, large trichodragma, f, small middle sized trichodragma, g, tiny (micro-)trichodragma.