Cadlina umiushi Korshunova, Picton, Sanamyan & Martynov, 2015

Do, Thinh Dinh, Jung, Dae-Wui, Kil, Hyun-Jong & Kim, Chang-Bae, 2020, A report of a new species and new record of Cadlina (Nudibranchia, Cadlinidae) from South Korea, ZooKeys 996, pp. 1-18 : 1

Cadlina umiushi Korshunova, Picton, Sanamyan & Martynov, 2015 Figures 2 , 4B

Cadlina umiushi Korshunova, Picton, Sanamyan & Martynov, 2015 in Martynov et al. 2015: 65, fig. 1; Korshunova et al. 2020: 15, 29, figs 7, 15B.

Cadlina olgae Chichvarkhin, 2016: 12-14, fig. 4.

Material examined.

One individual, voucher NIBRIV0000865972; South Korea, Gangwon-do, Goseong-gun, Jugwang-myeon, Munamjin-ri; 38°18'14.75"N, 128°34'1.05"E; collected on 02 June 2013 (COI GenBank number: MT420435). One individual, voucher SMU00060; South Korea, Gangwon-do, Goseong-gun, Jugwang-myeon, Munamjin-ri; 38°18'14.75"N, 128°34'1.05"E; collected on 02 June 2013 (COI GenBank number: MT420436).

Description.

Body ovate, 8 mm and 9 mm long. Living specimens with a translucent white dorsum (Fig. 2A ). Small yellow glands are present on both sides of the dorsum margin. Thin yellow marginal band present. Dorsum broad, rounded anteriorly and posteriorly. Small yellow tubercles cover the entire dorsum. Rhinophores long and broad. Six multipinnate gills connected by a membrane into circle around anus. Gills retractable into gill cavity. Foot broad, anteriorly thickened. Radula formula: 55 × 16.1.16. Rachidian tooth moderately high, trapezoid, and bearing four denticles (Fig. 2B ). Innermost lateral tooth massive with one cusp, two inner denticles, and three outer denticles. Second lateral tooth with one cusp, no inner denticles and three outer denticles. Mid-lateral tooth hamate, 6-8 distinct outer denticles (Fig. 2C ). Outer lateral tooth almost straight, denticles small, inconspicuous (Fig. 2D ). Reproductive system triaulic (Fig. 4B ). Ampulla long, wide, convoluted. Prostate moderate in length and wide, transiting to vas deferens. Vas deferens relatively short. Penis armed with spines. Vagina relatively short and broad, connecting with oval bursa copulatrix. Bursa copulatrix ca. 2 × larger than receptaculum seminis. Uterine duct short and narrow, connecting from female gland mass to base of ovate receptaculum seminis.

Remarks.

Cadlina umiushi was first described in Martynov et al. (2015) from the holotype specimen collected in Peter the Great Bay, Russia. Cadlina olgae Chichvarkhin, 2016, described from specimens collected in south of Rudnaya Bay, Russia is considered a junior synonym of C. umiushi by Korshunova et al. (2020). This study records the presence of C. umiushi in Korean waters for the first time. Even though there were slight differences in the number of denticles of the rachidian and the first lateral tooth, and in the ampulla compartments of specimens collected from South Korea compared to the specimens collected from Russia, other morphological characteristics are similar. It should be noted that this difference is also observed between specimens in Russia collected by Chichvarkhin (2016) and Korshunova et al. (2020). The differences could be explained by the geographical distribution or maybe a different stage of development. The maximum intraspecific distances in C. umiushi are 1.56% for the COI marker and 1.37% for the 16S rRNA marker (Suppl. material 1: Table S3). The lowest COI interspecific distance of 4.33% is found between C. umiushi and C. laevis (Linnaeus, 1767). The lowest 16S rRNA interspecific distance of 1.37% is found between C. umiushi and C. kamchatica .

Distribution.

Northern part of Sea of Japan (Russia) to Munamjin-ri (South Korea).

Figures

Figure 2. Cadlina umiushi A body; Radula B rachidian teeth C central and lateral region D outer lateral region. Scale bars: 2 mm (A); 10 μm (B); 50 μm (C); 20 μm (D).

Figure 4. Reproductive systems of Cadlina species A Cadlina koreana sp. nov. B Cadlina umiushi C Cadlina japonica. Abbreviations: a, ampulla; bc, bursa copulatrix; fgm, female gland mass; rs, receptaculum seminis; pr, prostate; sv, seminal vesicle; ud, uterine duct; v, vaginal duct; vd, vas deferens. Scale bars: 0.5 mm (A, B); 2 mm (C).