Gymnodoris nagoensis, Souza-Canal & Ángel & Valdés, 2025

Souza-Canal, Jade De, Ángel, Rie Nakano & Valdés, Ángel, 2025, Gymnodoris nigricolor Baba, 1960 (Mollusca, Nudibranchia, Polyceridae) is a species complex, Zoosystema 47 (17), pp. 315-326 : 324

Gymnodoris nagoensis n. sp.

( Figs 2K ; 3E, F ; 4E, F )

urn:lsid:zoobank.org:act:4EAC8527-DA41-4C9A-A3DD-AB36DFDCA528

TYPE MATERIAL. — Holotype. Japan • specimen 6 mm preserved length, dissected; Okinawa Prefecture; Nago; Kouki ; 26°32.8’N, 127°57.7’E; 31.V.2012; 10 m; isolate JP01 ; NSMT-Mo 79540.

OTHER MATERIAL EXAMINED.— Japan • 2 specimens 4 mm preserved length, dissected; Okinawa Prefecture, Ginowan, Sunabe ; 26°19.4’N, 127°44.6’E; 23.II.2010; 16 m; NSMT-Mo 79541 • 1 specimen 4 mm preserved length, dissected; Kagoshima Prefecture; Amami Ōshima Island; Tebiro Beach ; 28°24.1’N, 129°37.2’E; 9.III.2010; 9 m; NSMT-Mo 79542 .

ETYMOLOGY. — Named after Nago, Okinawa Prefecture, Japan, the type locality of this species.

DESCRIPTION

Body elongate, smooth, lacking tubercles ( Fig. 2K ). 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 elongate, conical, not fused together at base.Rhinophoral club occupying entire visible length, with transverse five lamellae. Gill composed of 10 simple gill leaves, lacking lamellae, arranged in a circle.

Radular formulae 18 × 11.1.0.1. 11 in a 4 mm-long specimen (NSMT-Mo 79541) and 18 × 12.1.0.1. 12 in a 6 mm-long specimen (NSMT-Mo 79540). Rachidian teeth absent. Innermost lateral teeth hamate, with very elongate, curved cusp, no denticles ( Fig. 3E ). Outer later teeth much smaller than innermost teeth, further decreasing in size gradually towards outer edge, hamate with wide base, long curved cusp ( Fig. 3F ). Labial cuticle smooth.

Reproductive system ( Fig. 4E ) with simple, pyriform ampulla connecting to both female gland, prostate. Prostate tubular, curved, much narrower than female gland. Prostate narrowing into relatively convoluted duct before expanding into short deferent duct. Deferent duct narrower than ampulla at its widest point. Vagina slightly curved, as wide as deferent duct, connecting directly into bursa copulatrix. Seminal receptacle small, oval, connecting to large, nearly spherical bursa copulatrix, in expanded region near vaginal connection; uterine duct short, connecting to female gland complex. Bursa copulatrix several times as large as seminal receptacle. Penis with 200- 300 mm-long, elongate spines with narrow bases, elongate cusps ( Fig. 4F ).

BIOLOGY

Found on sandy/silty bottoms at depths of 3-30 meters on Okinawa and Amami Ōshima island. When individuals of G. nagoensis n. sp. find a goby hole, they crawl into it. It seems that the nudibranch feeds on the fins of the goby; sometimes several individuals feed on the fins of a goby at the same time.

REMARKS

Gymnodoris nagoensis n. sp. is genetically very similar to G. nigricolor Baba, 1960 (Supplementary material 2; Fig.1B ) and recovered as the same species in the ASAP analysis but distinct in the bPTP analysis. Unfortunately, we were only able to amplify COI from one specimen despite multiple attempts. However, G. nagoensis n. sp. is anatomically different from all other species here examined. Externally, the rhinophores of G. nagoensis n. sp. are proportionally longer and have a reduced number of branchial leaves. The radular morphology of G. nagoensis n. sp. is similar to that of G. boussionae n. sp. but clearly distinct from that of G. nigricolor . The innermost teeth of G. nagoensis n. sp. are very elongate in comparison to mid-lateral teeth and lack denticles, whereas the innermost teeth of G. nigricolor are approximately the same size as the mid-lateral teeth, with truncated triangles, a large central conical cusp, and two lateral flat cusps. The teeth of G. nagoensis n. sp. are very similar to those of G. boussionae n. sp. even though these two species are phylogenetically more distant, and their reproductive anatomy is substantially different. The reproductive anatomy of G. nagoensis n. sp. is unique, having large, elongate penial spines with small bases, a bursa copulatrix several times larger than the seminal receptacle and a very short deferent duct. This combination of traits is not present in G. boussionae n. sp. or G. nigricolor and clearly differentiates G. nagoensis n. sp. from the other two species.

Figures

FIG. 2.— Photographs of live animals of the Gymnodoris nigricolor species complex: A, B, Gymnodoris nigricolor Baba, 1960, specimen MNHN-IM-2019-26208, isolate JD67 (A), specimen MNHN-IM-2019-26209, isolate JD27 (B); C-J, Gymnodoris boussionae n. sp. specimen MNHN-IM-2019-26204, isolate JD23 (C), specimen MNHN-IM-2019-26203, isolate JD35 (D), specimen MNHN-IM-2019-26206, isolate JD41 (E), specimen MNHN-IM-2019-26200, isolate JD43 (F), specimen MNHN-IM-2019-26205, isolate JD39 (G), specimen MNHN-IM-2019-26299, isolate JD51 (H), specimen MNHN-IM-2019-26207, isolate JD44 (I), specimen MNHN-IM-2019-26201, isolate JD10 (J); K, Gymnodoris nagoensis n. sp., specimen from Sunabe,Okinawa Prefecture,Japan,NSMT-Mo 79541,photo H.Tokura.

FIG. 3.— SEM of the radula of the Gymnodoris nigricolor species complex: A, B, Gymnodoris nigricolor Baba, 1960, specimen MNHN-IM-2019-26209, isolate JD27, innermost teeth (A) and outer lateral teeth (B); C-D, Gymnodoris boussionae n. sp., specimen MNHN-IM-2019-26203, isolate JD35, innermost teeth (C) and outer lateral teeth (D); E-F, Gymnodoris nagoensis n. sp., specimen from Sunabe, Okinawa Prefecture, Japan, NSMT-Mo 79541, innermost teeth (E) and outer lateral teeth (F). Scale bars: A, 30 μm; B, D, 20 μm; C, 30 μm; E, F, 10 μm.

FIG. 4.— Drawings of the reproductive system of the Gymnodoris nigricolor species complex: A, B, Gymnodoris nigricolor Baba, 1960, specimen MNHN- IM-2019-26209, isolate JD27, reproductive system (A) and penial spines (B); C, D, Gymnodoris boussionae n. sp., specimen MNHN-IM-2019-26203, isolate JD35, reproductive system (C) and penial spines (D); E, F, Gymnodoris nagoensis n. sp. specimen from Sunabe, Okinawa Prefecture, Japan, NSMT-Mo 79541, reproductive system (E) and penial spines (F). Scale bars: A, C, E, 1 mm; B, D, F, 100 μm. Abbreviations: see Material and methods.

FIG. 1.— A, histogram representing the distance plot for the ASAP analysis using the COI gene showing pairwise p-distances; B, consensus phylogenetic tree of specimens sequenced based on Bayesian analysis of the three concatenated loci. Posterior probabilities from Bayesian inference (BI) are given above branches and percentages corresponding to maximum likelihood bootstrap support are given below branches. Supported nodes are highlighted in blue, not supported nodes are highlighted in orange. Results of two species delimitation analyses are indicated by vertical bars.