Sclerodoris dutertrei, 2023

Innabi, Julie, Stout, Carla C. & Valdes, Angel, 2023, Seven new " cryptic " species of Discodorididae (Mollusca, Gastropoda, Nudibranchia) from New Caledonia, ZooKeys 1152, pp. 45-95 : 45

" Sclerodoris dutertrei " sp. nov.

Figs 14B-D , 15G , 16D-F

Type material.

Holotype: Anse de Koumac, New Caledonia (20°34.2'S, 164°16.5'E), 0 m depth [Koumac 2.1 stn. KR213], 11 Sep 2018, 31 mm long (MNHN IM-2013-86193, isolate JI04).

Material examined.

Recif Sud de Pandop , Koumac, New Caledonia (20°35.4'S, 164°16.5'E), 0 m depth [Koumac 2.1 stn. KR322, reef flat with rocks, living and dead corals], 27 Sep 2018, 1 specimen 23 mm long (MNHN IM-2013-86196, isolate JI14). Koumac, New Caledonia (20°35.6'S, 164°16.3'E), 3 m depth [Koumac 2.2 stn. KR230], 2 Mar 2019, 1 specimen 12 mm long (MNHN IM-2013-86194, isolate JI35); 1 specimen 20 mm long, dissected (MNHN IM-2013-86195, isolate JI34) .

Description.

Body oval, flattened, with an irregular, coriaceous texture (Fig. 14B-D ). Branchial and rhinophoral sheaths somewhat elevated, simple, irregular. Gill composed of five short, tripinnate branchial leaves, arranged upright. Rhinophores short, lamellated, with 12-14 lamellae. Visceral hump elevated over the rest of the mantle. Dorsum completely covered with small caryophyllidia and a complex network of ridges and scattered large, rounded tubercles. Body color variable, yellow to pale brown with scattered opaque white pigment and some specimens with rounded black spots. Branchial leaves are the same color as the dorsum; rhinophores brown proximally, with white apices.

Reproductive system (Fig. 15G ) with a long, wide, convoluted ampulla with several folds, which connects with the female gland complex and the oval, flattened prostate. The prostate narrows substantially into a long, convoluted duct, before expanding into the short, wide deferent duct. The penis is unarmed. The vagina is elongate, much narrower than the deferent duct, connecting directly to the large, oval bursa copulatrix. The elongate seminal receptacle also connects to the bursa copulatrix next to the vaginal connection, and the short uterine duct that enters the female gland complex. The seminal receptable possesses a spherical tip and it is similar in volume to the bursa copulatrix. An accessory gland connects to the genial atrium where the deferent duct and the vagina meet. The accessory gland is granular in texture and approximately as large as the bursa copulatrix.

Radular formula 37 × 54.0.54 in a 20-mm long specimen (MNHN IM-2013-86195). Rachidian teeth absent. Inner and mid-lateral teeth hamate, having a short cusp and lacking denticles (Fig. 16D, E ). Innermost teeth very small in comparison to mid-laterals (Fig. 16D ). The teeth increase in size gradually towards the medial portion of the half-row. Outermost teeth small, decreasing in size gradually, elongate, with a short cusp and lacking differentiated denticles (Fig. 16F ). No jaw was observed, labial cuticle smooth.

Biology.

Found under rocks at 0-3 m depth. All the specimens were obtained by direct collection while SCUBA diving. The specimens were very cryptic on rocks with sponges and other encrusting organisms.

Etymology.

This species is named after Valentine Dutertre whose hard work, dedication, and skill were critical for the collection of numerous important sea slug species during the Koumac expeditions.

Remarks.

The phylogenetic analysis places " Sclerodoris " Sclerodoris dutertrei sp. nov. in a well-supported clade containing two other species identified as members of Sclerodoris . These two species were sequenced and submitted to GenBank but never formally studied, thus their morphological characteristics remain undescribed. This clade is not closely related to the clade containing the rest of the species of Sclerodoris , including the type species, Sclerodoris tuberculata . Therefore, " S. " Sclerodoris dutertrei sp. nov. cannot be definitely included in the genus Sclerodoris and the generic placement of this species is regarded as tentative until a well resolved phylogeny of the Discodorididae permits a more accurate taxonomic placement. " Sclerodoris " Sclerodoris dutertrei sp. nov. is tentatively placed in Sclerodoris (as indicated by the quotation marks) because anatomically this species is for the most part consistent with the diagnosis for Sclerodoris provided by Valdés and Gosliner (2001), including a flattened, coriaceous dorsum covered with caryophyllidia, rhinophoral sheaths somewhat elevated; a lobate accessory gland, without stylet; labial cuticle and radular teeth smooth, hamate with the outermost lateral teeth multidenticulate. The only exception is the penis, which appears to be unarmed in " S. " Sclerodoris dutertrei sp. nov., but the presence of penial spines is a characteristic of Sclerodoris sensu stricto (see Valdés and Gosliner 2001).

" Sclerodoris " Sclerodoris dutertrei sp. nov. is distinct from other species previously assigned to Sclerodoris : no other species described to date possesses a yellow to pale brown dorsum with scattered opaque white pigment (sometimes with rounded black spots), completely covered with small caryophyllidia and a complex network of ridges and scattered large, rounded tubercles. As mentioned above, Sclerodoris tuberculata is red with several large, irregularly shaped, opaque white patches and a conspicuous depression mid-length on the dorsum, not present in " Sclerodoris " Sclerodoris dutertrei sp. nov.; Sclerodoris faninozi sp. nov. is yellowish brown, with scattered opaque white pigment, and areas of dark brown and dark gray but also has a longitudinal ridge, and several large, rounded tubercles, also absent in " Sclerodoris " Sclerodoris dutertrei sp. nov. Other Indo-Pacific species described also present external characteristics that distinguish them from " Sclerodoris " Sclerodoris dutertrei sp. nov. For example, Sclerodoris apiculata (Alder & Hancock, 1864) is characterized by having a network of ridges radiating from elevated conical centers, each with an elongated filament (see Alder and Hancock 1864; Hervé 2010; Gosliner et al. 2018; Nakano 2018). Sclerodoris coriacea has the dorsum completely covered with large, elongate tubercles joined by conspicuous ridges (see Rudman 1978; Gosliner et al. 2018), very different from those in " Sclerodoris " Sclerodoris dutertrei sp. nov. Sclerodoris japonica (Eliot, 1913), originally described as a member of the genus Halgerda (see Eliot 1913) is characterized by having a yellowish grey dorsum covered with small ridges, and numerous, large roundish areas of a darker grey, varying in intensity, which correspond to dorsal depressions or pits. Sclerodoris rubicunda is a red species with two large patches of white and purple pigment and a series of conspicuous dorsal ridges ( Baba 1949; Gosliner et al. 2018; Nakano 2018). Sclerodoris trenberthi (Burn, 1962b) and Sclerodoris tarka Burn, 1969 both described from Victoria, Australia are also distinct from " Sclerodoris " Sclerodoris dutertrei sp. nov. Sclerodoris trenberthi has a characteristic longitudinal dorsal structure composed of "irregularly sized and spaced low hard pustules surmounting a low ridge" running from the rhinophores to the gill ( Burn 1962b), which is absent from " Sclerodoris " Sclerodoris dutertrei sp. nov. Sclerodoris tarka is a dusky yellow to yellowish orange species with a pattern of conspicuous dorsal ridges (Burn, 1969) and an indistinct medial ridge, also absent in " Sclerodoris " Sclerodoris dutertrei sp. nov. Finally, Sclerodoris virgulata Valdés, 2001 is the only species of Sclerodoris with a white dorsum lacking dorsal ridges or depressions ( Valdés 2001), also very different from " Sclerodoris " Sclerodoris dutertrei sp. nov.

Figures

Figure 14. Photographs of live animals of the genus Sclerodoris Eliot, 1904 A Sclerodoris tuberculata Eliot, 1904, MNHN IM- 2013 - 86197 on black background B-D " Sclerodoris " Sclerodoris dutertrei sp. nov., Holotype (MNHN IM- 2013 - 86193) on black background (B), MNHN IM- 2013 - 86195 on black background (C), MNHN IM- 2013 - 86194 on black background (D) E Sclerodoris faninozi sp. nov., Holotype (MNHN IM- 2013 - 86198) on black background.

Figure 15. Drawing of the reproductive system of specimens of the genus Sclerodoris Eliot, 1904 A-C Sclerodoris tuberculata Eliot, 1904, MNHN IM- 2013 - 86197, general view (A), detail of the bursa copulatrix and seminal receptable (B), penial spines (C) D-F Sclerodoris faninozi sp. nov., Holotype (MNHN IM- 2013 - 86198), general view (D), detail of the bursa copulatrix and seminal receptable (E), penial spines (F) G " Sclerodoris " Sclerodoris dutertrei sp. nov., MNHN IM- 2013 - 86193. Abbreviations: ag, accessory gland; am, ampulla; bc, bursa copulatrix; dd, deferent duct; fg, female gland complex; pr, prostate; sr, seminal receptacle; vg, vagina.

Figure 16. SEM of the radula of specimens of the genus Sclerodoris Eliot, 1904 A-C Sclerodoris tuberculata Eliot, 1904, MNHN IM- 2013 - 86197, innermost teeth (A), mid-lateral teeth (B), outer lateral teeth (C) D-F " Sclerodoris " Sclerodoris dutertrei sp. nov., MNHN IM- 2013 - 86195, innermost teeth (D), mid-lateral teeth (E), outer lateral teeth (F) G-I Sclerodoris faninozi sp. nov., Holotype (MNHN IM- 2013 - 86198), innermost teeth (G), mid-lateral teeth (H), outer lateral teeth (I).