Gymnodoris inornata ( Bergh, 1880 )

Gymnodoris inornata ( Bergh, 1880) View in CoL

( Fig. 5 View FIGURE 5 )

Trevelyana inornata Bergh, 1880: 186–190 View in CoL , pl. 3, figs. 14–17, pl. 4, figs. 8–14, pl. 5, figs. 1–9. Type locality: Nagasaki, Japan.? Trevelyana kouaouae Risbec, 1928: 184 View in CoL , text fig. 56, pl. 7, fig. 3. Type locality: Kouaoua Bay, New Caledonia, 600 m depth.

Material examined. New Caledonia: North Province: Koumac, Ilôt Double ( 20°28'S, 164°07.7'E), 0 m depth [ Koumac 2.3 Expedition , stn. KM700 ], 28 Oct 2019, 1 specimen 13 mm preserved length (MNHN-IM-2019-26375, isolate JD48); 1 specimen 9 mm preserved length (MNHN-IM-2019-26376, isolate JD47) GoogleMaps . New Caledonia: North Province: Koumac, Margin of barrier reef flat ( 20°36.3'S, 164°07'E), 3 m depth [ Koumac 2.3 Expedition , stn. KR923, slab, debris and sand, coral patches], 23 Nov 2019, 1 specimen 5 mm preserved length (MNHN-IM-2019- 26377, isolate JD49) GoogleMaps . New Caledonia: South Province: Nouméa, Rocher à la Voile ( 20°18.19'S, 166°26.02'E), 2 m depth [ Quinzaine des Nudibranches Expedition , stn. QNPF-LA, night dive], 14 Sep 2022, 1 specimen 4 mm preserved length (MNHN-IM-2019-26379, isolate JD127) GoogleMaps . New Caledonia: North Province: Poum, South Yandé ( 20°4.57'S, 163°49.59'E), 0 m depth [ABC Poum Expedition, stn. ABC58 ], 20 Jun 2023, 1 specimen 13 mm preserved length (MNHN-IM-2019-26378, isolate JD126) GoogleMaps . New Caledonia: Loyalty Is.: Ouvéa, Tiberia ( 20°28.5'S, 166°35.66'E) [ Quinzaine des Nudibranches Ouvéa Expedition , stn. QUP29 ], 13 Jan 2024, 1 specimen 12 mm preserved length (MNHN-IM-2019-26491, isolate JD179) GoogleMaps . New Caledonia: Loyalty Is.: Ouvéa, Tiberia ( 20°28.5'S, 166°35.66'E) [ Quinzaine des Nudibranches Ouvéa Expedition , stn. QUP36 ], 14 Jan 2024, 1 specimen 4 mm preserved length (MNHN-IM-2019-26492, isolate JD173) GoogleMaps . New Caledonia: Loyalty Is.: Ouvéa, Pont de Mouly ( 20°41.91'S, 166°28.33'E), 5 m depth [ Quinzaine des Nudibranches Ouvéa Expedition , stn. QUP37, night dive], 14 Jan 2024, 1 specimen 6 mm preserved length (MNHN-IM-2019-26487, isolate JD171); 1 specimen 10 mm preserved length (MNHN-IM-2019-26488, isolate JD180); 1 specimen 5 mm preserved length (MNHN-IM-2019- 26489, isolate JD158) GoogleMaps . New Caledonia: Loyalty Is.: Ouvéa ( 20°36.93'S, 166°31.4'E) [ Quinzaine des Nudibranches Ouvéa Expedition , stn. QUP53 ], 17 Jan 2024, 1 specimen 4 mm preserved length (MNHN-IM-2019-26490, isolate JD157) GoogleMaps . New Caledonia: North Province: Poindimié, Tibarama ( 20°55.3'S, 165°22.4'E), 10 m depth, 17 Oct 2023, 1 specimen 4 mm preserved length [fringing reef with sand, seagrass] (MNHN-IM-2019-26493, isolate JD160), leg. A. Doulas. GoogleMaps

Description. Body oval to elongated, with numerous low, round tubercles ( Fig. 5 View FIGURE 5 ). Velum distinct, with 10 small tubercles; notal rim absent, velum merges into notum posterior to rhinophores. Posterior end of foot tapering slightly into broad “tail.” Color translucent orange-red, with dark red tubercles. Internal organs somewhat visible through body wall as white-orange mass, yellow network of glandular structures visible anterior to gill. Rhinophores bulbous with 12–14 lamellae, translucent white stalk, red club. Gill with 10 large, broad, tripinnate, red leaves, forming circle around anus. Foot wider than notum, surrounded by orange line; oral tentacles conspicuous, flat, with central fold.

Phylogenetic position. Gymnodoris inornata and its possible sister species Gymnodoris impudica (PP: 0.99, MLB: 67) were recovered in a clade also containing Gymnodoris tuberculosa ( Fig. 1A View FIGURE 1 ) and several undescribed species: Gymnodoris sp. 8 , Gymnodoris sp. F , Gymnodoris sp. G , Gymnodoris sp. H , and Gymnodoris knutsonae sp. nov. (PP: 0.93, MLB: 85) ( Fig. 1A View FIGURE 1 ).

Remarks. Bergh (1880) originally described Trevelyana inornata based on two specimens collected in Nagasaki, Japan, characterized by having a yellowish-white background color, blue-gray on the posterior third of the body due to the viscera being visible through, and rhinophores and gill with the same color as the rest of the body. Whereas this description is ambiguous, the name Gymnodoris inornata has been applied to a yellow-orange species with the rhinophores and the gill having the same color, which is consistent with the original description (see Yonow, 2011). But in most records from the Western Pacific, specimens assigned to G. inornata also possess darker red spots all over the body more or less visible (see Koh, 2006; Hervé, 2010; Nakano, 2018; Gosliner et al., 2018; Kil et al., 2020), as in the material here examined. It is unclear whether all these records are conspecific with the original description of G. inornata . Based on molecular species delimitation analyses, the material from New Caledonia examined herein belongs to the same species that Knutson & Gosliner (2022) identified as G. inornata , and therefore the specimens are tentatively assigned to this species, until further research clarifies the status of the name.

Risbec (1928) introduced Trevelyana kouaouae based on a single specimen dredged from 600 m depth in Kouaoua Bay, New Caledonia. The animal was described as brick colored, dotted with dark red, but with the background color varying with the internal organs, which are visible through transparency (brown posteriorly and white mass anteriorly). This description matches perfectly with that of the specimens here examined, albeit they were collected in shallow waters. If G. inornata is found to be a species complex, and the specimens with more conspicuous red dots ( Hervé, 2010; Gosliner et al., 2018) are distinct from uniformly colored specimens ( Yonow, 2011) or those with less clear dots ( Koh, 2006; Nakano, 2018; Kil et al., 2020), then the name G. kouaouae would be possibly more appropriate for the former.

This species was reported from Poindimié and Nouméa by Hervé (2010) as Gymnodoris inornata and Gymnodoris sp. 1 .