Mycale (Naviculina) mascarenensis Van & Aryasari & De 2021, sp.nov.
Creators: name: Van, Rob W. M.
name: Aryasari, Ratih
name: De, Nicole J.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Demospongiae
Poecilosclerida
Mycalidae
Mycale
Mycale mascarenensis

description: 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).
description: Published as part of Van, Rob W. M., Aryasari, Ratih & De, Nicole J., 2021, Mycale species of the tropical Indo-West Pacific (Porifera, Demospongiae, Poecilosclerida), pp. 1-212 in Zootaxa 4912 (1) on pages 154-156, DOI: 10.11646/zootaxa.4912.1.1, http://zenodo.org/record/4450930