Gymnodoris ceylonica (Kelaart, 1858)

Souza-Canal, Jade De & Valdés, Ángel, 2025, The genus Gymnodoris Stimpson, 1855 (Mollusca, Nudibranchia) in New Caledonia, with descriptions of eleven new species, Zootaxa 5710 (1), pp. 1-73 : 26-27

Gymnodoris ceylonica (Kelaart, 1858)

( Fig. 2M )

Trevelyana ceylonica Kelaart, 1858a: 257–258 , pl. 10B, figs. 1–2. Type locality: Sober Island, Sri-Lanka.

Trevelyana picta Pease, 1871: 301–302 , pl. 20, fig. 1. Type locality: “Island of Huaheine” [= Huahine , French Polynesia].

Trevelyana rubromaculata Bergh, 1905: 189–191 , pl. 3, fig. 14, pl. 17, figs. 21–23. On the reefs of Pepela Bay on the east coast of “Rotti Island” [= Rote Island, Indonesia].

Material examined. New Caledonia: South Province: Nouméa, Passe de Dumbea ( 22°21.8'S, 166°15.4'E), 6 m depth, 23 Oct 2022, 1 specimen 29 mm preserved length (MNHN-IM-2019-26504, not sequenced), leg. Y. Thévenet.

Description. Body oval to elongated, with several large, low, round tubercles. Velum distinct with several tubercles on edge; notal rim not differentiated, velum merges with dorsum behind rhinophores ( Fig. 2M ). Posterior end of foot tapering slightly into broad “tail.” Color translucent dirty-white, with orange-red tubercles. Rhinophores elongated, with 8 lamellae, translucent white stalk, pale orange club. Gill with 12 large, broad, tripinnate leaves, opaque white, main rachises orange-red. Foot wider than notum, surrounded by pale orange line. Oral tentacles small, blunt, orange.

Phylogenetic position. The phylogenetic position of Gymnodoris ceylonica is unresolved ( Fig. 1A ), it was recovered in a clade containing two undescribed species: Gymnodoris sp. 10 and Gymnodoris sp. 11, but support for this clade is lacking (PP: 0.5, MLB: 85). However, the monophyly of this species is well supported (PP: 1, MLB: 100) ( Fig. 1A ).

Remarks. Trevelyana ceylonica is a well characterized species first introduced from Sri-Lanka by Kelaart (1858a) and described again a few months later by Kelaart (1858b) as T. zeylanica [sic.] with the same text and no illustration. The original description by Kelaart (1858a) indicates the body color is white spotted with small dark orange-red spots, set wide apart from each other, the rhinophores are translucent basally and orange apically, and the branchial leaves are pure white, with a longitudinal bright-red streak on the back of each. These characteristics match the current usage of the name in the binomen G. ceylonica (e.g., Yonow, 2008; Nakano, 2018; Gosliner et al., 2018) and the specimen here illustrated ( Fig. 2M ). Unfortunately, the single specimen obtained herein could not be amplified for genetic analysis to further confirm the identification.

Pease (1871) described Trevelyana picta from Huahine, French Polynesia, as pale watery white in color, with conspicuously marked, remote, bright orange red circular spots, some of which are elevated, forming rounded tubercles. This description as well as the illustration provided ( Pease, 1871: pl. 20, fig. 1) match the current usage of the name G. ceylonica ( Yonow, 2008; Nakano, 2018; Gosliner et al., 2018) and these two names are clearly synonymous as already indicated by Rudman (1999).

Trevelyana rubromaculata was originally described by Bergh (1905) from Indonesia as bluish to yellowish species, with scattered bright red, round spots everywhere; rhinophores red, gill bluish-white with red rachises. This color pattern matches the original description of G. ceylonica . Also, the color illustration of the live animal ( Bergh, 1905, pl. 3, fig. 14) correspond to the current usage of the name G. ceylonica (see Yonow, 2008; Nakano, 2018; Gosliner et al., 2018). The synonymy of G. rubromaculata and G. ceylonica is further corroborated by the species delimitation analyses conducted herein, which recovered Indian Ocean and Western Pacific specimens as members of the same species, based on GenBank sequences.

Gymnodoris ceylonica was reported from New Caledonia by Risbec (1928) in Canala Bay and by Hervé (2010) in Bourail; these descriptions and illustrations match the characteristics of this species.

Figures

FIGURE 1. A. Bayesian consensus phylogenetic tree of the concatenated dataset including PP above branches and MLB below branches. Branches fully supported (PP: 1, MLB: 100) marked with asterisks. New species described in this paper highlighted in red font and illustrated; other species reported from New Caledonia in this study highlighted in blue font. Clades are collapsed according to the results of the ASAP and bPTP species delimitation analyses. B. Histogram representing the distance plot from the ASAP analysis using the COI gene showing pairwise p-distances (Kimura 2 model) among candidate species. The dashed line represents the distance threshold provided by the lowest ASAP score for species delimitation.

FIGURE 2. Gymnodoris impudica (Rüppell & Leuckart, 1830) and Gymnodoris ceylonica (Kelaart, 1858), photographs of live animals showing color variation. A. G. impudica, specimen from Koumac, New Caledonia (MNHN-IM-2019-26363, isolate JD09). B. G. impudica, specimen from Koumac, New Caledonia (MNHN-IM-2019-26355, isolate JD18). C. G. impudica, specimen from Koumac, New Caledonia (MNHN-IM-2019-26358, isolate JD02). D. G. impudica, specimen from Koumac, New Caledonia (MNHN-IM-2019-26357, isolate JD92). E. Specimen from Koumac, New Caledonia (MNHN-IM-2019- 26364, isolate JD14). F. Specimen from Koumac, New Caledonia (MNHN-IM-2019-26360, isolate JD94). G. G. impudica, specimen from Koumac, New Caledonia (MNHN-IM-2019-26361, isolate JD93). H. G. impudica, specimen from Koumac, New Caledonia (MNHN-IM-2019-26359, isolate JD11). I. G. impudica, specimen from Koumac, New Caledonia (MNHN- IM-2019-26356, isolate JD15). J. Specimen from Koumac, New Caledonia (MNHN-IM-2019-26362, isolate JD95). K. G. impudica, specimen from Koumac, New Caledonia (MNHN-IM-2019-26427, not sequenced). L. G. impudica, specimen from Koumac, New Caledonia (MNHN-IM-2019-26426, isolate JD01). M. G. ceylonica, specimen from Nouméa, New Caledonia (MNHN-IM-2019-26504), photo Y. Thévenet.