Atagema kimberlyae, Innabi & Stout & Valdés, 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

Atagema kimberlyae sp. nov.

Figs 2C, D , 3B, C , 4D-F

Atagema sp. 2: Hervé 2010: 190.

Type material.

Holotype: Koumac, New Caledonia (20°35.5'S, 164°16.4'E), 5 m depth [Koumac 2.1 stn. KR223, patch of sponges, small bits of sedimented coral, coarse sand and mud with algae], 19 Sep 2018, 20 mm long, dissected (MNHN IM-2013-86191, isolate JI43).

Description.

Body oval, flattened, covered with small, irregular tubercles and short ridges decreasing in size towards the mantle margin (Fig. 2C, D ). A central, longitudinal area devoid of tubercles or ridges runs between the rhinophores and gill. A series of depressions on each side of the central ridge, generally decreasing in size towards the mantle margin. Entire dorsal surface, except for the depressions, covered with caryophyllidia. Branchial sheath composed of three large lobes; gill composed of five tripinnate branchial leaves, arranged horizontally in the living animal. Rhinophoral sheaths elevated; rhinophores long, lamellated, with 20 lamellae. Body color opaque greyish brown, with pale brown pigment mainly on top of the tubercles and ridges and scattered opaque white pigment; depressions dark brown to black (Fig. 2C ). Rhinophores and branchial leaves are the same color as the dorsum.

Reproductive system (Fig. 3B, C ) with a short, wide, simple ampulla that connects with the female gland complex and a convoluted prostate. The prostate has several folds and is approximately as wide as the ampulla. The prostate narrows slightly into a curved duct before expanding into the long, ovoid, wide deferent duct. At its widest point, the deferent duct is slightly wider than the prostate. The penis is unarmed. The vagina is long and narrow and connects directly to the spherical bursa copulatrix. The vagina is approximately as wide as the deferent duct. The small elongate seminal receptacle also connects to the bursa copulatrix near the vaginal connection and the short uterine duct that enters the female gland complex. The bursa copulatrix is several times larger than the seminal receptacle (Fig. 3C ).

Radular formula 15 × 20.0.20 in a 20-mm long specimen (MNHN IM-2013-86191). Rachidian teeth absent. Inner and mid-lateral teeth hamate, having a small cusp and lacking denticles (Fig. 4D-F ). Innermost teeth very small in comparison to mid-laterals (Fig. 4D ), elongate, with an inconspicuous secondary cusp mid-length. The teeth increase in size suddenly towards the medial portion of the half-row (Fig. 4E ). Outermost teeth small, decreasing in size gradually, and hamate (Fig. 4F ). No jaw was observed, labial cuticle smooth.

Biology.

Possibly a New Caledonia endemic, rare, 5 m depth. The single specimen was obtained while SCUBA diving by direct collection on an unidentified sponge on which it was highly cryptic.

Etymology.

This species is named after Kimberly García Mendez, who participated in two of the Koumac expeditions, collecting a number of specimens and helping enormously with the processing and photographing of samples.

Remarks.

Atagema kimberlyae sp. nov. is assigned to the genus Atagema for two reasons, 1) the molecular phylogenetic analysis places the specimens sequenced in a clade containing A. spongiosa , a well stablished member of this genus (see above); 2) the morphological characteristics of this new species are consistent with the diagnosis of the genus provided by Valdés and Gosliner (2001), including a flexible body with series of tubercles all covered with caryophyllidia and depressions, the anterior border of the branchial sheath composed of three lobes and the gill leaves arranged horizontally; furthermore the prostate is tubular, with a single portion, the penis and vagina are unarmed, the labial cuticle smooth, and all radular teeth are hamate and smooth.

Atagema kimberlyae sp. nov. is morphologically similar to Atagema spongiosa (described above), particularly to the juvenile specimens, but is genetically distinct. Also, it lacks the distinctive dorsal ridge of A. spongiosa and presents a number of anatomical differences, including a comparatively much shorter and wider ampulla, a wider prostate, a rounded bursa copulatrix instead of oval, and comparatively larger innermost lateral teeth. A review of the literature reveals that no other described Indo-Pacific species of Atagema are morphologically similar to A. kimberlyae sp. nov., hence it is described as new.

The geographic range of Atagema kimberlyae sp. nov. is close to that of Atagema molesta (Miller, 1989 as Trippa molesta ), introduced based on a single specimen collected from Te Hāwere-a-Maki (Goat Island), New Zealand. Miller (1989) described and illustrated the holotype, which differs from A. kimberlyae sp. nov. in several regards, including the more complex dorsal pattern of tubercles and ridges present in A. molesta , giving the animal a spikier appearance, and the reproductive system, which has a much larger deferent duct and a shorter prostate in A. kimberlyae sp. nov. While the radular morphology of the two species is similar, the radular formula is not, 23 × 32.0.32 in a 12-mm specimen of A. molesta versus 15 × 20.0.20 in a 20-mm long specimen of A. kimberlyae sp. nov.

Based on the species delimitation analysis presented here, A. kimberlyae sp. nov. is closely related but genetically distinct from specimens identified as Atagema cf. osseosa and Atagema notacristata whose sequences are deposited in GenBank.

Figures

Figure 2. Photographs of live animals of the genus Atagema Gray, 1850 A, B Atagema spongiosa (Kelaart, 1858), MNHN IM- 2013 - 86188 on black background (A), MNHN IM- 2013 - 86189 in situ (B) C, D Atagema kimberlyae sp. nov., MNHN IM- 2013 - 86191 on black background (C), MNHN IM- 2013 - 86191 in situ (D) E Atagema papillosa (Risbec, 1928), MNHN IM- 2013 - 86192 on black background.

Figure 3. Drawings of the reproductive systems of specimens of the genus Atagema Gray, 1850 A Atagema spongiosa (Kelaart, 1858), MNHN IM- 2013 - 86190 B, C Atagema kimberlyae sp. nov., MNHN IM- 2013 - 86191, general view (B), detail of the bursa copulatrix and seminal receptable (C) D, E Atagema papillosa (Risbec, 1928), MNHN IM- 2013 - 86192, general view (D), detail of the bursa copulatrix and seminal receptable (E). Abbreviations: am, ampulla; bc, bursa copulatrix; dd, deferent duct; fg, female gland complex; pr, prostate; sr, seminal receptacle; vg, vagina.

Figure 4. SEM of the radula of specimens of the genus Atagema Gray, 1850 A-C Atagema spongiosa (Kelaart, 1858), MNHN IM- 2013 - 86190, innermost teeth (A), mid-lateral teeth (B), outer lateral teeth (C) D-F Atagema kimberlyae sp. nov., MNHN IM- 2013 - 86191, innermost teeth (D), mid-lateral teeth (E), outer lateral teeth (F) G-I Atagema papillosa (Risbec, 1928), MNHN IM- 2013 - 86192, innermost teeth (G), mid-lateral teeth (H), outer lateral teeth (I).