Mycale (Naviculina) mascarenensis, 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 : 154-156

Mycale (Naviculina) mascarenensis sp.nov.

Figs 99 a–c, 100a–d, 101a–e

Material examined. Holotype RMNH Por. 11689, Rodrigues, Mourouk Ebony, Castel Rock , 19.7648°S S 63.4626E, 18 m depth, SCUBA, coll. N.J. de Voogd, field nr. ROG 103, 19 October 2016 (orange-brown).

Paratype RMNH Por. 11723, Rodrigues , Passe Grenade, 19.675S 63.4842E, 8 m depth , SCUBA, coll. N.J. de Voogd, field nr. ROG 140, 21 October 2016 (orange-brown) .

Description ( Figs 99 a–c, 100a–b). Massively encrusting on dead corals and rocks ( Figs 99 a–c), also consolidating coral rubble ( Figs 100 a–b). Color orange-brown, faintly punctate ( Fig. 99c ), surface not clearly reticulate. On deck, color turns more reddish orange. In preserved condition the specimens are collapsed and fragmented, and beige colored. The detachable skin is transparent and becomes largely loose from the pulpy choanosomal tisse. Size up to 5 x 3 x 2 cm (preserved holotype). Consistency soft.

Skeleton ( Figs 100 c-d). Choanosomal skeleton cavernous, with a basal spongin-rich spicule mass enveloping coral debris, from which issue comparatively thin spicule tracts, 50–150 µm in diameter, further thinning out near the surface to carry the ectosomal skeleton. The detachable tangential skeleton is parchment-like and consists of the usual aegogropila-type reticulation of intercrossing spicule tracts ( Fig. 100c ). These are comparatively thin, 15–35 µm, consisting of up to 4 spicules in cross section, meshes up to 300 µm in widest dimension. Rosettes of anisochelae, 70–100 µm in diameter ( Figs 100 c–d), as well as single anisochelae II and less frequent flagellated sigmas ( Fig. 99d ) are scattered between the sutface tracts.

Spicules ( Figs 101 a–e). Mycalostyles, three categories of anisochelae, flagellated sigmas (no ‘normal’ sigmas, no toxas).

Mycalostyles ( Figs 101a,a 1 ), straight, slim, with elongated, barely developed heads and pointed opposite ends, 318– 355.8 –399 x 3– 5.2 – 7 µm.

Anisochelae I ( Fig. 101b ), ‘normal’ shaped, with well-developed alae, upper median alae extended outward, free part of the shaft about 40% of spicule length, 33– 36.3 – 39 µm.

Anisochelae II ( Fig. 101c ), naviculichelae, squarish in outline, central plate leaving only small open spaces between the upper and lower alae, rims smooth or with slight upper bump, but not provided with spines, both sides slightly different, 24– 27.3 – 30 µm.

Anisochelae III ( Fig. 101d ), naviculichelae, oval in outline, 15– 17.1 – 19 µm.

Flagellated sigmas ( Figs 101e ), strongly curved, asymmetrical endings (reminding strongly of Mycale (Naviculina) diversisigmata Van Soest, 1984 ) (cf. Van Soest 2017: fig. 2), 47– 122.3 –201 x 36– 101.2 – 156 µm. No ‘normal’ sigmas I and II.

Distribution and ecology. Rodrigues, Mascarene Islands (dependency of Mauritius), on reefs, 8–18 m depth.

Etymology. Named after the island group of the Mascarenes to which the type locality Rodrigues belongs.

Remarks. So far, the new species appears to be endemic to the island of Rodrigues. It is obviously closely related to M. (N.) cleistochela , which shares the possession of flagellated sigmas as well as the ‘normal’ anisochelae I and naviculichelae II and III. The two specimens described here differ clearly from M. (N.) cleistochela in lacking toxas and ‘normal’ sigmas. Also the in situ shapes and surface characters are clearly different (cf. Figs 93 and 99 ).

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 93. Mycale (Naviculina) cleistochela Vacelet & Vasseur, 1971, habitus, a, RMNH Por. 1904 in situ, from Bali, Indonesia (photo N.J. de Voogd), b, ditto preserved, c, ZMA Por. 15126 preserved, from SW Sulawesi, Indonesia (scale bar = 1 cm).

FIGURE 99. Mycale (Naviculina) mascarenensis sp.nov., habitus in situ, a, holotype RMNH Por. 11689 from Rodrigues, b, paratype RMNH Por. 11723, also from Rodrigues, c, detail of holotype showing punctate surface (photos N.J. de Voogd).

FIGURE 100. Mycale (Naviculina) mascarenensis sp.nov., habitus and skeleton of holotype RMNH Por. 11689, from Rodrigues, a, on deck, b, detail of preserved specimen (scale bar = 1 cm), c, light microscopic image of ectosomal skeleton showing intercrossing spicule tracts and rosettes of anisochelae I, d, details of skeleton with flagellated sigma, rosettes of anisochelae and scattered naviculichelae.

FIGURE 101. Mycale (Naviculina) mascarenensis sp.nov., SEM images of spicules of holotype RMNH Por. 11723, from Rodrigues, a, mycalostyle, a1, details of mycalostyle, b, anisochela I, c, anisochelae II, d, anisochela III (anisochela II and III same scale), e, flagellated sigmas.