Gymnodoris sp. 9

Gymnodoris sp. 9

( Figs. 11A–K View FIGURE 11 )

Material examined. New Caledonia: North Province: Koumac, Ilôt Rat ( 20°33.4'S, 164°10.9'E), 0 m depth [ Koumac 2.1 Expedition, stn. KM200 , sand-mud flat with seagrass; reef flat, rocky shore with living/dead corals], 4 Sep 2018, 1 specimen 8 mm preserved length (MNHN-IM-2019-26394, isolate JD59) GoogleMaps . New Caledonia: North Province: Koumac, Infernet Reef ( 20°37.1'S, 164°15'E), 3 m depth [ Koumac 2.1 Expedition, stn. KR302, at the foot of the reef, sandy sediment with silt, coral debris, and seagrass], 7 Sep 2018, 1 specimen 5 mm preserved length (MNHN-IM-2019-26435, isolate JD70) GoogleMaps . New Caledonia: North Province: Koumac, Ilôt Kendec ( 20°40.1'S, 164°15.4'E), 0 m depth [ Koumac 2.1 Expedition, stn. KM302 , living corals, coral rubble, sand patches], 9 Sep 2018, 1 specimen 10 mm preserved length (MNHN-IM-2019-26395, isolate JD07) GoogleMaps . New Caledonia: South Province: Nouméa, Ilôt Song, Ouémo ( 22°16.91'S, 166°28.84'E), 1–6 m depth [Quinzaine des Nudibranches Expedition, stn. QNPF-DA, detrital sandy-muddy, live Porites ], 6 Sep 2022, 1 specimen 9 mm preserved length (MNHN-IM-2019-26396, isolate JD85) GoogleMaps . New Caledonia: South Province: Ouémo, Platier Ricaudy ( 22°18.67'S, 166°27.49'E), 0.5 m depth [Quinzaine des Nudibranches Expedition, stn. QNAV-FA], 4 Sep 2022, 1 specimen 6 mm preserved length (MNHN-IM-2019-26436, isolate JD131) GoogleMaps . New Caledonia: North Province: Poum , Mouac Is. ( 20°12.84'S, 164°0.61'E), 0 m depth [ABC Poum Expedition, stn. ABC46 ], 18 Jun 2023, 1 specimen 7 mm preserved length (MNHN-IM-2019-26434, isolate JD140) GoogleMaps . New Caledonia: North Province: Poum, Bay of the Grotte ( 20°2'S, 163°47.92'E), 0 m depth [ABC Poum Expedition, stn. ABC52 ], 19 Jun 2023, 1 specimen 7 mm preserved length (MNHN-IM-2019-26431, isolate JD122); 1 specimen 7 mm preserved length (MNHN-IM-2019-26432, isolate JD141) GoogleMaps . New Caledonia: North Province: Poum , Mouac Is. ( 20°13.02'S, 164°1.4'E), 0 m depth [ABC Poum Expedition, stn. ABC63 ], 21 Jun 2023, 1 specimen 9 mm preserved length (MNHN-IM-2019-26433, isolate JD99) GoogleMaps . New Caledonia: Loyalty Is.: Ouvéa, Pont de Mouly ( 20°41.91'S, 166°28.33'E) [Quinzaine des Nudibranches Ouvéa Expedition, stn. QUP63, night dive], 18 Jan 2024, 1 specimen 9 mm preserved length (MNHN-IM-2019-26516, isolate JD153) GoogleMaps . New Caledonia: South Province: Nouméa, Ilôt Song ( 22°16.91'S, 166°28.84'E), 10 m depth, 28 Jun 2022, 1 specimen 11 mm preserved length (MNHN-IM-2019-26518, isolate JD144), leg. Y. Thévenet. GoogleMaps

Description. Body narrow, elongate, with numerous low, conical tubercles of varying sizes ( Figs. 11A–K View FIGURE 11 ). Anterior end of notum with distinct velum having 15–18 small papillae; notal rim absent, velum merges with notum behind rhinophores. Posterior end of foot broad, tapering into pointy “tail.” Color translucent white, tubercles, velum papillae yellow-orange; posterior end translucent grey. Internal organs, posterior branched glandular structure visible through body wall. Rhinophores bulbous with narrow tips, 12–14 lamellae, cream, brow, or reddish, with apical orange-red dot. Gill with 8 short, irregular, bipinnate leaves, translucent white, sometimes with small orange dots, opaque white bases, arranged in circle around anus, opened posteriorly. Foot wider than notum, translucent yellow. Oral tentacles large, flap-like.

Phylogenetic position. Gymnodoris sp. 9 is the most basal member of a well-supported clade (PP: 1, MLB: 100) also including Gymnodoris alba and Gymnodoris sp. 49, which are sister to one another (PP: 1, MLB: 100) ( Fig. 1A View FIGURE 1 ).

Remarks. This undescribed species is similar to G. citrina , both having the anterior margin of the head with a distinctive row of low tubercles, but the anterior end of the foot has two flap-like oral tentacles, instead of a well-developed but blunt oral tentacles in G. citrina . Moreover, G. citrina lacks a glandular structure behind the gill.

Gymnodoris sp. 9 appears to be widespread in the Indo-Pacific region ( Gosliner et al., 2018). Knutson & Gosliner (2022) studied specimens from Papua New Guinea, Vanuatu, and Saudi Arabia. Also, possibly reported from French Polynesia ( Boutet et al., 2020) as Gymnodoris sp. 2 , from Okinawa, Japan by Nakano (2018) as Gymnodoris sp. 17 and G. citrina (large photo), and from Hong Kong, China by Rudman & Darvell (1990: pl. 4, fig. C) as G. citrina atypical form. Very common in New Caledonia, it has possibly been reported from Nouméa by Hervé (2010) as Gymnodoris sp. 2 (small photo).