Goniobranchus sinensis (Rudman, 1985)

Soong, Giun Yee, Bonomo, Lynn J., Reimer, James D. & Gosliner, Terrence M., 2022, Battle of the bands: systematics and phylogeny of the white Goniobranchus nudibranchs with marginal bands (Nudibranchia, Chromodorididae), ZooKeys 1083, pp. 169-210 : 169

Goniobranchus sinensis (Rudman, 1985)

Figures 3a-d , 6a, b , 10a-f

Glossodoris marginata (Pease, 1860): Baba 1938: 11-12, fig. 8; Abe 1964: 47, pl. 21, fig. 74; Lin and Tchang 1965: 10, pl. 1, fig. 11 (misidentifications).

Chromodoris marginata (Pease, 1860): Orr 1981: 27 (misidentification)

Chromodoris sinensis Rudman, 1985: 83, 272-275, figs 12C, 13C, 14C, 15C, 18, 19; Gosliner et al. 2008: 219, bottom photograph.

Goniobranchus sinensis : Gosliner et al. 2015: 223, middle left photograph; Gosliner et al. 2018: 153, middle left photograph.

Type locality.

Hong Kong.

Type material.

AM C139295, one specimen, Fan Tsang Chau Island, 22.367°N, 114.400°E, Hong Kong, China, 10 m depth, 11 August 1983. Type material not examined due to high level of detailed work provided by the original description in Rudman (1985).

Geographical distribution.

This species appears to be restricted to areas of the southeast Asian mainland and the islands of Japan, Taiwan, and islands off eastern Peninsular Malaysia ( Debelius and Kuiter 2007; Coleman 2008; Gosliner et al. 2008, 2015, 2018) with reports from the Andaman Islands ( Kumar et al. 2019), the east coast of Thailand ( Mehrotra et al. 2021), the east coast of Peninsular Malaysia (present study), Japan ( Nakano 2018; Ono and Katou 2020), Taiwan ( Jie et al. 2009), Hong Kong ( Rudman 1985), and the Gulf of Oman (Fatemi and Attaran-Fariman 2015).

Material examined.

MISE-047-19 (morphotype A), one specimen, subsampled for molecular data and dissected, 31.281°N, 130.203°E, Kagoshima, Japan, 10 m depth, 14 July 2019, A. Tsuyuki. MISE-037-19 (morphotype A), one specimen, subsampled for molecular data, Sakurajima Evacuation Port Number 4, 31.552°N, 130.632°E, Kagoshima, Japan, 10 m depth, 10 July 2019, H. Kise. MISE-039-19 (morphotype A), one specimen, subsampled for molecular data, east side of Okiko-jima, 31.544°N, 130.617°E, Kagoshima, Japan, 8 m depth, 12 July 2019, G. Y. Soong. MISE-010-19 (morphotype B), one specimen, subsampled for molecular data and dissected, Tengan, 26.400°N, 127.833°E, Okinawa-jima Island , Japan, 8 m depth, 3 May 2019, G. Y. Soong. MISE-056-19 (morphotype B), one specimen, subsampled for molecular data, Tengan, 26.400°N, 127.833°E, Okinawa-jima Island , Japan, 12 m depth, 27 October 2019, G. Y. Soong. MISE-024-18 (morphotype B), one specimen, subsampled for molecular data, Tengan, 26.400°N, 127.833° E, Okinawa-jima Island , Japan, 7 m depth, 12 April 2018, G. Y. Soong. MISE-024-19 (morphotype B), one specimen, subsampled for molecular data, Tengan, 26.400°N, 127.833°E, Okinawa-jima Island , Japan, 5 m depth, 16 June 2019, Y. Kushida. MISE-009-19 (morphotype B), one specimen, subsampled for molecular data, Tengan, 26.400°N, 127.833°E, Okinawa-jima Island , Japan, 8 m depth, 3 May 2019, G. Y. Soong. MISE-055-19 (morphotype B), one specimen, subsampled for molecular data, Tengan, 26.400°N, 127.833°E, Okinawa-jima Island , Japan, 8 m depth, 27 October 2019, H. Kise. MISE-020-18 (morphotype B), one specimen, subsampled for molecular data, Tengan, 26.400°N, 127.833°E, Okinawa-jima Island , Japan, 9 m depth, 12 April 2018, G. Y. Soong. MISE-010-19 (morphotype B), one specimen, subsampled for molecular data, Tengan, 26.400°N, 127.833°E, Okinawa-jima Island , Japan, 8 m depth, 3 May 2019, G. Y. Soong. MISE-023-18 (morphotype B), one specimen, subsampled for molecular data, Tengan, 26.400°N, 127.833°E, Okinawa-jima Island , Japan, 7 m depth, 12 April 2018, G. Y. Soong. MISE-018-19 (morphotype B), one specimen, subsampled for molecular data, Red Beach, 26.447°N, 127.912°E, Okinawa-jima Island , Japan, 6 m depth, 19 May 2019, G. Y. Soong. MISE-022-18 (morphotype B), one specimen, subsampled for molecular data, Tengan, 26.400°N, 127.833°E, Okinawa-jima Island , Japan, 10 m depth, 12 April 2018, G. Y. Soong. MISE-008-19 (morphotype B), one specimen, subsampled for molecular data, Tengan, 26.400°N, 127.833°E, Okinawa-jima Island, Japan, 8 m depth, 3 May 2019, G. Y. Soong. CASIZ 176759 (morphotype C), one specimen, subsampled for molecular data, Waterfall Bay, 2.720°N, 104.195°E, Pulau Tioman, South China Sea, Peninsular Malaysia, 14 m depth, 4 October 2007, T.M. Gosliner et al. CASIZ 175727 (morphotype C), one specimen (2 mm preserved), subsampled for molecular data, Pulau Gut, 2.664°N, 104.167°E, Pulau Tioman, South China Sea, Peninsular Malaysia. 14 m depth, 4 October 2007, T.M. Gosliner. CASIZ 189457 (morphotype C), one specimen (3 mm preserved), subsampled for molecular data, location not available, GPS data not available, Peninsular Malaysia, depth not available, 4 October 2007, T.M. Gosliner .

Description.

External morphology. Living animal ~ 10 mm in length. Body smooth, without tubercles, oval and elongated, with three marginal bands on the mantle edge. Seven to ten unipinnate gill branches, 13-18 rhinophore lamellae. The species has three distinct morphotypes based on color patterns. Morphotype A (Fig. 3a ) has a translucent creamy white body with no spots on the notum. The outermost portion of the mantle edge is surrounded by a thin whitish blue band, followed by one each of thicker red and yellow bands. The gill and rhinophores are translucent red with reddish purple edges. Morphotype B (Fig. 3b, c ) has a translucent white body with brown spots on the notum. The outermost portion of the mantle edge is surrounded by an opaque bluish white tinged band, followed by red and yellow submarginal bands, and all three bands have similar widths. The gill and rhinophores are translucent red with opaque white edges. Morphotype C (Fig. 3d ) has a creamy white but translucent body with fine orange spots on the notum. The outermost portion of the mantle edge is surrounded by a thin opaque bluish white tinged band, followed by a thicker irregular red band, and then a yellow submarginal band of similar thickness to the red band. Gill and rhinophores are translucent red with reddish purple edges.

Buccal mass and radula (morphotype A). The muscular portion of the buccal mass approximately the same size as the oral tube length (Fig. 6a ). The chitinous labial cuticle found at the anterior end of the muscular portion of the buccal mass bearing bifurcated and long jaw rodlets (Fig. 10a, b ). The radular formula of MISE-010-19 and MISE-047-19 (Fig. 10c ) are 46 × 40.1.40 and 52 × 40.1.40, respectively. The rachidian tooth is triangular, thin, with a blunt tip. The innermost lateral teeth have two or three denticles on the inner side and 3-5 denticles on the outer side of the central cusp (Fig. 10d ). The central cusp on the inner lateral tooth is elongate and ~ 2 × the length of the adjacent denticles. The middle lateral teeth have a short central cusp with six or seven denticles (Fig. 10e ). The outer lateral teeth have a rounded main cusp with five denticles (Fig. 10f ).

Reproductive system (Fig. 6b ). The thick, tubular ampulla narrows into a diverging short oviduct and long vas deferens. The proximal prostatic portion of the vas deferens is thin and convoluted and transitions into the muscular ejaculatory portion. The long, narrow, convoluted ejaculatory portion transitions into a wider and long curved penial bulb, which joins with the distal end of the vagina. The vagina is narrow and elongated and transitions into a larger, spherical bursa copulatrix and the smaller, curved receptaculum seminis at its distal end. A moderately long uterine duct emerges from this junction of vagina, bursa, and receptaculum seminis. The uterine duct connects the receptaculum seminis with the female gland mass. The female gland mass has smaller albumen and membrane glands and a larger mucous gland.

Remarks.

Our G. sinensis morphotype A specimens are the same as Rudman’s (1985) specimens; all of Rudman’s (1985) specimens were collected from Hong Kong. He only found one morphotype, with a translucent creamy white body and the outermost portion of the mantle edge surrounded by a thin white band, followed by one each of thicker red and yellow bands. The gill and rhinophores were translucent red with reddish purple edges. Some of the specimens he collected also had fine orange-brown specks on the notum; however, this morphological trait was observed in comparatively few of the newly collected specimens and is found in morphotype C (Fig. 3d ). Rudman (1985) also synonymized specimens documented by Baba (1938) and Abe (1964) from Japan as G. sinensis , further supporting the identification of our specimens from Kagoshima, Japan as G. sinensis . Morphotype A has thus been reported from Hong Kong and Japan. In our study, we also observed two more morphotypes of G. sinensis : morphotype B from Okinawa, Japan and morphotype C from Peninsular Malaysia.

Goniobranchus sinensis demonstrates intraspecific variation (intraspecific p -COI distance within G. sinensis = 0.0-1.4%) in morphology based on geographic location, with specimens collected from Peninsular Malaysia, Okinawa, and mainland Japan in this study. Body patterns of nudibranchs can vary depending on environmental factors ( Rudman 1991), and this may explain the morphological variation in G. sinensis as observed by Rudman (1991) and in the current study. Distinctive features of the external morphology are included in the remarks for G. preciosus , the species with which this species has been most frequently confused.

Figures

Figure 3. a-d Goniobranchus sinensis a CASIZ 176759, morphotype A, Peninsular Malaysia b MISE- 018 - 19, morphotype B, Okinawa, Japan c MISE- 55 - 19, morphotype B, Okinawa, Japan d MISE- 039 - 19, morphotype C, Kagoshima, Japan e, f Goniobranchus verrieri e CASIZ 203059, morphotype A, Philippines f CASIZ 208442, morphotype B, Philippines. Photographs a, e, f TMG; b-d GYS. Scale bars: 1 cm.

Figure 6. a buccal mass of Goniobranchus sinensis, MISE- 047 - 19 b reproductive system of Goniobranchus sinensis, MISE- 047 - 19 c buccal mass of Goniobranchus verrieri, CASIZ 203059 d reproductive system of Goniobranchus verrieri, CASIZ 203059 e bBuccal mass of Goniobranchus fabulus sp. nov., CASIZ 191271 f reproductive system of Goniobranchus fabulus sp. nov., CASIZ 191271. Abbreviations: am, ampulla; bb, buccal bulb; bc, bursa copulatrix; ej, ejaculatory duct; es, esophagus; fgm, female gland mass; ot, oral tube; p, penis; pr, prostate; ra, radular sac; rs, receptaculum seminis; va, vagina. Scale bars: 0.1 mm (c, d, e, f); 1 mm (a, b).

Figure 10. Scanning electron micrographs. Goniobranchus sinensis, MISE- 047 - 19, Kagoshima, Japan. a jaw b jaw rodlets c radula d central teeth e mid-lateral teeth f outer lateral teeth.