Cadlina umiushi Korshunova, Picton, Sanamyan et Martynov, 2015

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 : 72-74

Cadlina umiushi Korshunova, Picton, Sanamyan et Martynov, 2015

( Figs 1C–E, H, I, L, M, P ; 2A)

Material studied: MIMB48043 , 1 specimen, dissected, the Sea of Okhotsk , Aniva Bay , Moguchi River, Hirano ridge, 46°05.372’N, 142°13.612’E, 20 m in depth, 20.08.2013, coll. A. Plaksin,A. Semenov. MIMB48042 , 1 specimen, dissected, same locality, date and collectors as MIMB48043 .

Type locality: Sea of Japan, Peter the Great Bay , Bolshoy Pelis Is., 5–7 m depth.

Diagnosis: Length 13–24 mm (preserved specimens). Notum semitransparent white, rounded anteriorly, 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 to trifid or rarely unicuspidal rodlets. Radular formula: 73 × 21–27.1.21–27. Rachidian tooth trapezoid, elongate, slightly narrowed apically, with 5–7 denticles, sometimes with bifurcations, inner denticles larger than outer denticles. Lateral teeth hook-shaped with up to 12 denticles. Reproductive system triaulic ( Fig. 2A). Ampulla massive, convoluted, muscular. Penis armed with small, densely arranged hamate spines. Vas deferens long and winding, with long expanded prostatic part, narrowing near penis. Receptaculum seminis small, oval; bursa copulatrix large, rounded, muscular.

Molecular data: A BLAST-n search of COI sequence resulted 99.53% identical to 2 sequences of Cadlina umiushi (type specimens, MN224067 and MN224068) thus confirming the species identity of our samples.

Distribution: This species was originally described from the Sea of Japan, Peter the Great Bay and adjacent areas, e.g. Spokoinaya Bay, Rudnaya Bay [ Martynov et al., 2015a,b; Korshunova et al., 2020a; Chichvarkhin, 2016]. It was discovered further south, in the Sea of Japan waters of South Korea [ Do et al., 2020]. Our results extend the geographical range of this species to southern parts of the Sea of Okhotsk (Aniva Bay).

Remarks: Specimens from Aniva Bay show slight morphological differences from the type specimens of C. umiushi : the latter have mostly bifid and rarely trifid rodlets of the labial cuticle, and their rachidian teeth are trapezoid, bearing 5–6 denticles almost equal in size or slightly larger [ Korshunova et al., 2020a]. In specimens from Aniva Bay the rodlets are commonly bifid and trifid, with rare unicuspid elements ( Fig. 1H ), the rachidian tooth is elongated trapezoid, commonly with 5–6 large denticles among which central denticles are the largest.

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.