Gymnodoris boussionae Souza-Canal, Ángel & Valdés, 2025, n. sp.

Gymnodoris boussionae n. sp. (Figs 2C; 3C, D; 4C, D) urn:lsid:zoobank.org:act: ED997B72-5312-4C15-A9B7-AC8582A9BFCF TYPE MATERIAL. — Holotype. New Caledonia • specimen 10 mm preserved length; Koumac; East of Karembé; 20°39.1’S, 164°17.6’E; 6 m; 26.IX.2018; Koumac 2.1 Stn KR 633; isolate JD41; MNHNIM-2019-26206. OTHER MATERIAL EXAMINED. — New Caledonia • 1 specimen 7 mm preserved length, dissected; Koumac; Reef of Infernet; 20°36.7’S, 164°14.7’E; 5 m; 6.IX.2018; Koumac 2.1 Stn KR 301; isolate JD35; MNHN-IM-2019-26203 • 1 specimen 7 mm preserved length; Koumac; East of Karembé; 20°39.6’S, 164°17.5’E; 2-5 m; 27.IX.2018; Koumac 2.1 Stn KR 636; isolate JD23; MNHNIM-2019-26204 • 1 specimen 11 mm preserved length; isolate JD43; MNHN-IM-2019-26200 • 1 specimen 11 mm preserved length; isolate JD44; MNHN-IM-2019-26207 • 1 specimen 5 mm preserved length, dissected; isolate JD68; MNHN-IM-2019-26202 • 1 specimen 9 mm preserved length, dissected; isolate JD39; MNHN-IM-2019-26205 • 1 specimen 6 mm preserved length, dissected; Koumac; 20°38.4’S, 164°16.5’E; 28.II.2019; Koumac 2.2 Stn KR 252; isolate JD51; MNHN-IM-2019-26199 • 1 specimen 8 mm preserved length; Koumac; 20°33.3’S, 164°12.7’E, 4 m; 4.XI.2019; Koumac 2.3 Stn KR 90; isolate JD106; MNHNIM-2019-26201 • 1 specimen 4 mm preserved length; Poum, Ouanne; 20°20.73’S, 164°1.22’E; 0 m; 11. VI.2023; ABC Poum Stn ABC04; isolate JD114; MNHN-IM-2019-26524. ETYMOLOGY. — This species is named in honor of Magali Boussion diver and underwater videographer from New Caledonia, in appreciation for her participation in several sea slug collecting expeditions and documentation of the behavior of this species in nature. DESCRIPTION Body elongate, smooth, lacking tubercles (Fig. 2 D-J). Body color velvet black, with blurry neon-blue lines visible on mantle margin under certain light conditions. Rhinophores and branchial leaves with same color as dorsum. Rhinophores short, conical, not fused together at base. Rhinophoral club occupying entire visible length, with 10 transverse lamellae. Gill composed of 16-19 simple leaves, arranged in a circle. Radular formulae 19 × 13.1.0.1. 13 in a 5 mm-long specimen (MNHN-IM-2019-26202, isolate JD68), 27 × 16.1.0.1. 16 in a 6 mm-long specimen (MNHN-IM-2019-26199, isolate JD51), and 29 × 18.1.0.1. 18 in a 8 mm-long specimen (MNHN-IM-2019-26203, isolate JD35). Rachidian teeth absent. Innermost lateral teeth hamate, with very elongate, curved cusp, no denticles (Fig. 3C). Outer later teeth much smaller than innermost teeth, further decreasing in size gradually towards outer edge, hamate with wide base, long curved cusp (Fig. 3D). Labial cuticle smooth. Reproductive system (Fig. 4C) with elongate, simple, narrow ampulla, connecting to both female gland, prostate. Prostate flat, almost as wide as female gland. Prostate narrowing into long, curved duct before expanding into long, convoluted deferent duct. Deferent duct narrower than ampulla at widest point. Vagina straight, wider than ampulla, curving before connecting directly into bursa copulatrix. Seminal receptacle small, elongated, connecting to oval bursa copulatrix opposite to vaginal connection; uterine duct short, connecting to female gland complex. Bursa copulatrix twice as large as seminal receptacle. Penis with 200 mm-long spines with curved cusps and long bases (Fig. 4D). BIOLOGY Possibly an endemic from New Caledonia, rare, 5 m. The specimens were collected by direct collection while scuba diving. The feeding behavior was not observed. REMARKS With the exception of G. nigricolor and the specimen from the Marshall Islands assigned to G. cf. nigricolor by Knutson & Gosliner (2022), there are no other species of Gymnodoris described to date with a uniformly velvet black body color (see Gosliner et al. 2018; Knutson & Gosliner 2022). Thus, G. boussionae n. sp. is externally clearly distinguishable from all other species of Gymnodoris. There are several differences between G. boussionae n. sp. and G. nigricolor that justify the description of a new species. First, these two species are consistently recovered as distinct groups in all species delimitation analyses. Second, the radular of G. boussionae n. sp. is clearly different from that of G. nigricolor, having the innermost teeth curved, very elongate in comparison to mid-lateral teeth, whereas in G. nigricolor the innermost teeth are short, each tooth with a central cusp and fewer hamate outer teeth. Third, the reproductive system of G. boussionae n. sp. contains small penial spines (200 Μm) with elongate bases and curved cusps, and a broad flattened prostate, whereas the spines of G. nigricolor are larger (200-400 mm) and elongate, and the prostate is tubular. Fourth, the rhinophores of G. boussionae n. sp. are separate at the base, but they are fused together at the base in G. nigricolor. There are no morphological descriptions available of the specimen from Marshall Islands to compare the radula or reproductive system with the specimens of G. boussionae n. sp. here described. However, the former species is clearly distinct as it is consistently recovered in a different group in all species delimitation analyses, and it is not closely related to G. boussionae n. sp. in the phylogenetic analyses. Other authors are currently working on the description of the specimen from the Marshall Islands (Gosliner, pers. comm.).