Cadlina sp.

Ekimova, Irina A., Grishina, Darya Yu. & Nikitenko, Ekaterina D., 2024, Nudibranch molluscs of Sakhalin Island, Northwestern Pacific: new records and descriptions of two new species, Ruthenica, Russian Malacological Journal 34 (2), pp. 69-91 : 75-76

Cadlina sp.

( Figs 1A, B, F, G, K, N, O ; 2B)

Material studied: MIMB48044 , 1 specimen, the Sea of Okhotsk , Aniva Bay, Anastasia Cape, 46°00.727’N, 142°10.671’E, 5–15 m in depth, 22.08.2023, coll. A. Plaksin, A. Semenov . MIMB48045 , MIMB48046 , 2 specimens, dissected, collection locality, date and collectors are same as MIMB48044 .

Diagnosis: Length 20–26 mm (preserved specimens). Notum semitransparent white, rounded in front and posteriorly, covered with numerous yellow rounded spots on dorsal side. Large yellow subepidermal glands on dorsolateral sides of notum. Well-defined yellow line around notal edge. Buccal bulb with labial cuticle, formed by bifid rodlets. Radular formula: 67 × 17–24.1.17–24. Rachidian tooth trapezoid, with 4–5 denticles, almost equal in size. Lateral teeth hook-shaped with up to 18 denticles. Reproductive system triaulic ( Fig. 2B). Ampulla large, slightly convoluted. Penis armed with small, densely arranged hamate spines. Prostatic part of vas deferens long and winding, non-prostatic portion of vas deferens formed several dense loops near penial sheath. Receptaculum seminis small, oval; bursa copulatrix large, rounded, muscular, connecting to vagina by wide duct.

Molecular data: On both Bayesian (BI) and Maximum likelihood (ML) phylogenetic trees ( Fig. 3) Cadlina sp. from Aniva Bay was recovered as a derived monophyletic group (posterior probability from BI, PP = 1; bootstrap support from ML, BS = 100). This clade is sister to monophyletic group, uniting Atlantic species of the Cadlina laevis (Linnaeus, 1767) species complex (PP = 0.94; BS = 80). The C. laevis species complex includes С. kamchatica Korshunova et al., 2015 from Kamchatka, C. laevis s.str. from NE Atlantic and Arctic, Cadlina sp. and C. paninae Korshunova et al., 2020 from the Kurile Islands, Cadlina koreana Do et al., 2020 from the Sea of Japan and Cadlina umiushi from the Sea of Japan and Aniva Bay (PP = 1; BS = 87).

Distribution: This species is found only in the Sea of Okhotsk, Aniva Bay.

Remarks: This species shows similarities in external features with the sympatric species Cadlina umiushi ( Fig. 1 ): it has a semitrasparent notum, with yellow spots on the dorsal sides, well-defined subepidermal glands on the notal edges and a yellow line around the notal edge. Internally its radular morphology matches the description of Cadlina sp. from the Kuril Islands and the type specimens of Cadlina umiushi : [see Korshunova et al., 2020a for details]. At the same time, COI-based genetic data shows high divergence from all species comprising the C. laevis species complex [ C. laevis , C. kamchatica , C. paninae , C. umiushi , Cadlina sp. sensu Ekimova et al., 2021a] and thus, most likely the species from Aniva Bay represents a new species for science. The complicated taxonomy of the Cadlina laevis species group has been already highlighted in the previous studies [ Korshunova et al., 2020a; Ekimova et al., 2021a]. Here we follow the suggestion by Ekimova et al. [2021a] that further studies of NW Pacific specimens are needed to confirm the species status of putative Cadlina new taxa due to the high level of variation in external and internal characters and the limited available material for study.

Figures

FIG. 1. External and internal morphology of Cadlina spp. from Aniva Bay. A. Cadlina sp. MIMB48044. B. Cadlina sp., MIMB48045. C. Cadlina umiushi, MIMB48042. D. Cadlina umiushi, MIMB48043. E. Cadlina umiushi, MIMB48042, in natural environment. F. Cadlina sp., MIMB48045, labial cuticle rodlets. G. Cadlina sp., MIMB48045, radula. H. Cadlina umiushi, MIMB48043, labial cuticle rodlets. I. Cadlina umiushi, MIMB48043, radula. K, N, O. Cadlina sp., MIMB48045, anterior radular portion, details of teeth morphology. L, M, P. Cadlina umiushi, MIMB48043, anterior radular portion, details of teeth morphology. Scale bars: F, H, N = 20 µm; G, I = 250 µm; K = 100 µm; L = 10 µm; M, O, P = 50 µm. Photo credits: A – D. Anton Plaksin; E. Alexander Semenov. РИС. 1. ВнешнЯЯ и внутреннЯЯ морфологиЯ Cadlina spp. иЗ Залива Анива. A. Cadlina sp. MIMB48044. B. Cadlina sp., MIMB48045. C. Cadlina umiushi, MIMB48042. D. Cadlina umiushi, MIMB48043. E. Cadlina umiushi, MIMB48042 в естественной среде. F. Cadlina sp., MIMB48045, родлеты лабиальной кутикулы. G. Cadlina sp., MIMB48045, радула. H. Cadlina umiushi, MIMB48043, родлеты лабиальной кутикулы. I. Cadlina umiushi, MIMB48043, радула. K, N, O. Cadlina sp., MIMB48045, переднЯЯ часть радулы, детали морфологии Зубов. L, M, P. Cadlina umiushi, MIMB48043, переднЯЯ часть радулы, детали морфологии Зубов. Масштабные линейки: F, H, N = 20 µm; G, I = 250 µm; K = 100 µm; L = 10 µm; M, O, P = 50 µm. Авторство фотографий: A – D. Антон Плаксин; E. Александр Семенов.