Cadlina japonica Baba, 1937

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 japonica Baba, 1937 Figures 3 , 4C

Cadlina japonica Baba, 1937: 76-78, fig. 1; Baba 1949: 57, pl. XXI, figs 75-77, text fig. 67; Choe and Lee 1994: 362, fig. 2; Nakano 2018: 275; Korshunova et al. 2020: 36-39, figs 11, 12.

Material examined.

Two individuals, vouchers: NIBRIV0000865973 and NIBRIV0000865974; 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 and 20 July 2019 (COI GenBank numbers: MT420432 and MT420433). One individual, voucher NIBRIV0000865975; South Korea, Gyeongsangbuk-do, Uljin-gun, Uljin-eup, Yeonji-ri; 37°00'0.59"N, 129°26'1.89"E; collected on 25 August 2011 (COI GenBank number: MT420434).

Description.

Size up to 55 mm long. Live specimens commonly opaque white with a yellowish ground color and several dark brownish patches present on the dorsum (Fig. 3A ). Rhinophores yellowish like the ground color with bright yellow tips. Rhinophoral sheath bears small tubercles and yellow dots. Six multipinnate, translucent white gills with yellow tips. Yellow dots present irregularly on the dorsum, but often concentrated near the mantle margin. Continuous yellow band present on mantel edge. Oral tentacles short and triangular. Foot broad, anteriorly thickened to form a double edge. Radula formula: 88 × 71.1.71. Rachidian tooth elongate and bears 2-4 distinct lobe-like cusps (Fig. 3B ). Innermost lateral tooth hamate with a relatively narrow base and short, strong cusp; three or four inner denticles and 4-6 outer denticles (Fig. 3B ). Middle lateral teeth hook-shaped, no inner denticle and 3-5 outer denticles (Fig. 3C ). Outer lateral teeth bear up to six denticles (Fig. 3D ). Reproductive system triaulic (Fig. 4C ). Ampulla is moderate and convoluted. Prostate long and narrow. Vas deferens long, narrow, convoluted. Penial spines absent. Vagina relatively short, narrow and connects with bursa copulatrix. Bursa copulatrix almost rectangular in shape, ca. 5 × larger than receptaculum seminis. Uterine duct short and narrow.

Remarks.

Cadlina japonica was first described by Baba (1937). Recently, this species was thoroughly reviewed by Korshunova et al. (2020). Morphologically, the C. japonica specimens collected in this study are consistent with C. japonica described in previous studies ( Baba 1937; Choe and Lee 1994; Korshunova et al. 2020). Cadlina japonica is completely distinguishable from other species of the genus by several characteristics. Irregular brownish patches are present on the mantle, but these patches are absent on several small individuals. Its rachidian tooth is elongate and its first lateral tooth is hamate. In addition, compared to other Cadlina species in the region, C. japonica is large, with the sample in this study measuring up to 55 mm. The maximum intraspecific distances in C. japonica are 0.78% for the COI marker and 0.23% for the 16S rRNA marker (Suppl. material 1: Table S3). The lowest COI interspecific distance of 7.97% is found between C. japonica and C. jannanicholsae Korshunova et al., 2020. The lowest 16S rRNA interspecific distance of 1.87% is found between C. japonica and C. klasmalmbergi .

Distribution.

Southern Hokkaido to southern Honshu (Japan) and East Sea, South Korea (Sea of Japan).

Figures

Figure 3. Cadlina japonica A body; Radula B rachidian teeth C central and lateral region D outer lateral region. Scale bars: 1 cm (A); 20 μm (B); 100 μm (C); 50 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).