Atagema papillosa (Risbec, 1928)

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 papillosa (Risbec, 1928)

Figs 2E , 3D, E , 4G-I

Phlegmodoris papillosa Risbec, 1928: 90-91, pl. 8, fig. 2. Type locality: Nouméa, New Caledonia [not indicated in the original description], see Risbec (1953).

Trippa albata ? Trippa albata Burn, 1962a: 101-102, text fig. 5. Type locality: Sunderland Bay, Phillip Island, Victoria, Australia.

Atagema ? Atagema sp. 11: Gosliner et al. 2018: 116.

Material examined.

Koumac , New Caledonia (20°35.6'S, 164°16.2'E), 4-6 m depth [Koumac 2.3 stn. KD510, coral debris and coarse sand], 30 Oct 2019, 1 specimen 11 mm long, dissected (MNHN IM-2013-86192, isolate JI42) .

Description.

Body oval, flattened, covered with a complex network of small ridges with two levels of organization (Fig. 2E ). The largest ridges cover the entire body, leaving some depressions in between. Smaller ridges occur in the depressions dividing them into smaller fragments. 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 16 lamellae. Body color opaque grey with scattered yellow spots; depressions with gray ridges dividing dark grey to black fragments. Gill leaves are the same color as the dorsum. Rhinophores greyish to yellowish cream.

Reproductive system (Fig. 3D, E ) with a large, folded ampulla that connects with the female gland complex and an elongate prostate. The prostate is much longer and ~ 2 × as narrow as the ampulla. The prostate narrows substantially into a long, folded tube before expanding into the short, curved, wide deferent duct. The deferent duct is ~ 2 × as narrow as the prostate. The penis is unarmed. The vagina is long and narrow, slightly narrower than the deferent duct, and connects directly to the oval bursa copulatrix. The elongate seminal receptacle also connects to the bursa copulatrix next to the vaginal connection, and the short uterine duct, which enters the female gland complex. The bursa copulatrix is several times as large as the seminal receptacle (Fig. 3E ).

Radular formula 13 × 19.0.19 in a 11-mm long specimen (MNHN IM-2013-86192). Rachidian teeth absent. Inner and mid-lateral teeth hamate, having a small cusp and lacking denticles (Fig. 4G-I ). Innermost teeth very small in comparison to mid-laterals (Fig. 4G ), elongate, with an inconspicuous secondary cusp mid-length. The teeth increase in size suddenly towards the medial portion of the half-row (Fig. 4G ). Outermost teeth small, decreasing in size gradually, and hamate (Fig. 4I ). No jaw was observed, labial cuticle smooth.

Biology.

Possibly a New Caledonia endemic, rare, 4-6 m depth. The single specimen was collected by dredging on coral debris and coarse sand bottoms.

Remarks.

Phlegmodoris papillosa Risbec, 1928 was originally described based on a single specimen collected in Nouméa, New Caledonia, with a short description and an illustration of the live animal. Risbec (1928) described the species as having the notum covered with large papillae and bearing spots with the appearance of black ocelli standing out against a yellowish background. Risbec (1928) also mentioned that the elongated, perfoliate rhinophores of P. papillosa are retractile in funnel-shaped sheaths with a well-marked ocelliform spotted papilla; and the gill is retractile in a cavity with a star-shaped orifice. The specimens here examined closely resemble the original description of P. papillosa with the exception that the notum is grey, not yellowish.

Atagema albata (Burn, 1962a) is a similar species, originally described as Trippa albata , based on three specimens collected in Victoria, Australia. The specimens were described as pure white, sometimes with cream pigment, and characterized by having a soft, broad, flat body, with the mantle covered with low caryophyllidia, all similar in size, and with a mid-dorsal crest, extending from between the rhinophores to the branchial cavity. Burn (1962a) also described the branchial cavity as having an irregular outline and the rhinophores as perfoliate, with small, raised sheaths. Burn (1962a) compared T. albata with the New South Wales species T. intecta Kelaart, 1859 (= Goniodoris erinaceus Angas, 1864), which according to Burn (1962a) is usually much larger than A. albata and is of an ashy-brown color. With the available information is it not possible to confirm if A. albata and A. papillosa are the same species, and sequence data from A. albata would be needed to confirm this potential synonymy.

Finally, the specimen from the Philippines illustrated by Gosliner et al. (2018) as Atagema sp. 13 presents a similar external appearance and could be the same species. Examination of specimens is needed to confirm this possibility.

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).