Gymnodoris amakusana ( Baba, 1996 )

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 : 37-39

Gymnodoris amakusana ( Baba, 1996)

( Fig. 7C )

Analogium amakusanum Baba, 1996: 91–95 , fig. 1, pl. 1. Type locality: Notojima , Toyama Bay, Japan.

Material examined. New Caledonia: North Province: Koumac ( 20°35.1'S, 164°16.3'E), 7 m depth [Koumac 2.3 Expedition, stn. KR1019], 4 Nov 2019, 1 specimen 6 mm preserved length (MNHN-IM-2019-26461, isolate JD12) .

Description. Body oval to elongate, with several low, short longitudinal ridges, densely arranged anterior to gill ( Figs. 7C ). Velum and notal rim well differentiated, anterior and posterior ends narrowing into keel. Posterior end of foot tapering slightly into broad “tail.” Color opaque white, ridges and notal rim orange. Rhinophores with very broad stalk, bulbous club, 8 lamellae, club deep red, stalk white. Gill with 7 narrow, irregular, bipinnate leaves, opaque white, arranged is a transverse row. Foot wider than notum, opaque white, surrounded by orange line. Anterior end of foot greatly expanded, with two semicircular, orange oral tentacles.

Phylogenetic position. The phylogenetic analyses conducted herein were unable to determine the phylogenetic position of Gymnodoris amakusana ( Fig. 1A ).

Remarks. Baba (1996) described Gymnodoris amakusana from Toyama Bay, Japan as a translucent white species with the notal ridge completely bordered with a rich golden yellow line extending as far as to near the head, and a transverse bar of the same color just in front of the gill. This description as well as the color illustration in the original description ( Baba, 1996, pl. 1) matches the external characteristics of the material here examined from New Caledonia as well as other records in the literature ( Nakano, 2018; Gosliner et al., 2018, Kil et al., 2020). Previous to Baba’s (1996) description, members of this species were often identified as G. striata (e.g., Rudman & Darvell, 1990).

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 7. Gymnodoris nigricolor Baba, 1960, Gymnodoris amakusana (Baba, 1996), and Gymnodoris boussionae De Souza-Canal et al., 2024, photographs of live animals showing color variation. A. G. nigricolor, specimen from Koumac, New Caledonia (MNHN IM-2019-26208, isolate JD67). B. G. nigricolor, specimen from Koumac, New Caledonia (MNHN IM-2019-26209, isolate JD27). C. G. amakusana, specimen from Koumac, New Caledonia (MNHN-IM-2019-26461, isolate JD12). D. G. boussionae, specimen from Koumac, New Caledonia (MNHN IM-2019-26204, isolate JD23). E. G. boussionae, specimen from Koumac, New Caledonia (MNHN IM-2019-26203, isolate JD35). F. G. boussionae, specimen from Koumac, New Caledonia (MNHN IM-2019-26206, isolate JD41). G. G. boussionae, specimen from Koumac, New Caledonia (MNHN IM-2019-26200, isolate JD43). H. G. boussionae, specimen from Koumac, New Caledonia (MNHN IM-2019-26205, isolate JD39). I. G. boussionae, specimen from Koumac, New Caledonia (MNHN IM-2019-26299, isolate JD51). J. G. boussionae, specimen from Koumac, New Caledonia (MNHN IM-2019-26207, isolate JD44). K. G. boussionae, specimen from Koumac, New Caledonia (MNHN IM-2019-26201, isolate JD10). L. G. boussionae, specimen from Poum, New Caledonia (MNHN-IM- 2019-26524, isolate JD114).