Goniobranchus aureopurpureus ( Collingwood, 1881 )

Ishiyama, Haruki, Oya, Yuki, Wilson, Nerida G. & Kajihara, Hiroshi, 2024, Testing the Species Status of the Chromodorid Nudibranch Goniobranchus aureopurpureus (Mollusca: Gastropoda), Species Diversity 29 (1), pp. 141-150 : 144-147

Goniobranchus aureopurpureus ( Collingwood, 1881) ( Fig. 2A, B )

[Japanese name: Komon-umiushi]

Chromodoris aureopurpurea Collingwood, 1881: 129–130 , pl. 9, figs 18–22; Rudman 1987: 346–352, figs 23, 26–29 (in part); Baba 1989: 21–23, fig. 1; Hori and Fukuda 1996: 8, 32, figs 4, 25a–c; Suzuki 2000: 68; Nakano 2004: 156– 157; Dong 2006: 126.

“ Ch. aureo -purpurea, Coll., var?” [sic]: Fujita 1893: 164–165, fig. 4.

Glossodoris aureopurpurea : Baba 1935: 341–342, text-fig. 7, pl.

5, fig. 4; Baba 1949: 50, text-fig. 54, pl. 17, fig. 61; Abe and

Baba 1952: 264–265, figs 6, 9; Baba et al. 1956: 79, pl. 24,

fig. 5; Abe 1964: 46, pl. 20, fig. 73; Lin and Tchang 1965: 10. Glossodoris aureo -purpurea: Pruvot-Fol 1951: 86–87. Goniobranchus sp. cf. aureopurpureus : Nakano 2019b: 77. Goniobranchus cf. aureopurpureus : Nakano 2019a: 288. Goniobranchus aureopurpureus : Kashio and Yamazaki 2021:

3, fig. 2.

Material examined. ICHUM 6270.

Sequences. COI (658 bp), INSD accession number LC651157; 16S (416 bp), LC651158.

Description. Body 40 mm in length while alive. Mantle oblong; surface smooth. Rhinophore retractable, clubs lamellate. Branchial plumes retractable, 11 in number, situated around anus on posterior part of mantle. Oral tentacles conical, situated on both sides of mouth. Posterior end of foot almost overlapped by mantle.

Mantle surface white, covered with irregularly sized yellow spots; multiple violet spots arranged along mantle margin, mostly connected to each other forming single band; each violet spot containing darker area, latter usually situat- ed medially. Foot white. Rhinophore stalk proximally white, distally violet. Rhinophore clubs violet except for white lamellate edges. Branchial plumes violet.

Radula 2.0 mm long, 61,0,61 × 54. Lateral teeth slightly curved; each lateral tooth with 6–12 cusps along inner side of its distal end for short length (20–25 µm); cusps tightly arranged to each other, nearly perpendicular to long axis of lateral tooth ( Fig. 2B ).

Species distribution. The species seems to be distributed from the southern part of the East China Sea ( Collingwood 1881) northward along the Nansei Islands ( Nakano 2019a, b), Korea ( Dong 2006), and both the Pacific ( Fujita 1893; Baba 1935, 1949, 1989; Rudman 1987; Suzuki 2000; Nakano 2004) and the Japan Sea ( Abe and Baba 1952; Baba et al. 1956; Baba 1989; Hori and Fukuda 1996; Nakano 2004) coasts of Honshu Island to Hokkaido ( Kashio and Yamazaki 2021; present study). The type locality is one of many islands between Haitan (Pingtan) Island and mainland China, although the name “Slut Island” in the original description ( Collingwood 1881: 129) has apparently ceased to be used, probably because of its political incorrectness, making it difficult to locate the exact type locality.

Remarks. Although we were able to confirm the number of tooth rows as well as the number of teeth on each row under the stereomicroscope, the radula was largely lost during SEM preparation except for a fragment on the right side. Because the right-most lateral teeth of the fragment became unobservable due to their position on the SEM stub, we were unable to locate the position of each remaining tooth ( Fig. 2B ) relative to the central tooth on each row. We were also unable to examine the internal anatomy of the reproductive system due to a maloperation during preparation.

The present specimen agrees with the original description of Chromodoris aureopurpurea by Collingwood (1881) in that it possesses scattered yellow spots, multiple peripheral violet spots without yellow crescent, and violet rhinophores and gill. It differs from the original illustration in that the ground color of the mantle is white, instead of yellowish in the holotype ( Collingwood 1881: pl. 9, fig. 18). Also, the present specimen has 11 branchial plumes, while the holotype has only 10. According to Fujita (1893), however, the number of the branchial plumes can vary intraspecifically. Details of the radula in the holotype are unknown ( Collingwood 1881), and thus cannot be comparable with the present material. Meanwhile, the lateral teeth in our specimen possess cusps that abut tightly to each other and are almost perpendicular to the long axis of the tooth. These characteristics largely agree with those illustrated and described by Rudman (1987) for specimens from Japan, referred to as Chromodoris aureopurpurea .

Goniobranchus cf. variatus ( Risbec, 1928) comb. nov. [Japanese name: Minami-komon-umiushi] ( Fig. 2C )

Chromodoris aureopurpurata : Eliot 1906: 643 (spelling error).

? Chromodoris variata Risbec, 1928: 141–143 , fig. 37, pl. 5, fig. 10.

? Glossodoris variata : Pruvot-Fol 1951: 154; Risbec 1953: 67– 69, fig. 29.

Chromodoris sp. : Willan and Coleman 1984: 22–23, fig. 53.

Chromodoris aureopurpurea : Rudman 1987: 346–352, figs 23, 26–29 (in part); Wells and Bryce 1993: 118 (lower, 145); Coleman 2001: 68 (in part, excl. Moreton Bay); Tonozuka 2003: 82; Ono 2004: 166; Cobb and Willan 2006: 116 (no locality information); Debelius and Kuiter 2007: 163 (in part, possibly excl. Gulf of Thailand); Humann and Deloach 2010: 323 (no locality information).

Chromodoris rufomarginata : Debelius 1998: 210 (not Bergh 1890).

Goniobranchus aureopurpureus : Coleman 2008: 131 (in part, possibly excl. Malaysia); Gosliner et al. 2015: 225; Nakano 2019a: 288; Forster et al. 2021: fig. S1 (without figure number).

Material examined. WAM S112548.

Sequences. COI (594 bp), INSD accession number EU512128; 16S (405 bp), EU512055.

Description. Mantle rather uneven, with wart-like bumps. Rhinophore retractable, clubs lamellate. Branchial plumes retractable, simply pinnate, estimated to be 7 in number, situated around anus on posterior part of mantle. Preserved specimen with rhinophores and gills retracted.

Mantle white, speckled with yellow spots; edge ornament- ed with single row of violet spots arranged unevenly, some being submarginal, others being on edge, varying in shape from rounded to droplet-shaped, each bordered with light blue margin ( Fig. 2C ). Each lamella red except for white edge. Stalks red. Gill translucent with a reddish tinge.

Species distribution. Given that the species is identifiable by the external features, it seems to be distributed widely in the central Indo-Pacific, specifically from Western Australia ( Rudman 1987; Debelius and Kuiter 2007), north through Indonesia ( Debelius 1998; Tonozuka 2003; Debelius and Kuiter 2007; Coleman 2008), down Queensland— Great Barrier Reef ( Rudman 1987), Moreton Bay Region ( Willan and Coleman 1984; Coleman 2001), and New South Wales ( Rudman 1987; Wells and Bryce 1993; Debelius 1998; Debelius and Kuiter 2007; Forster et al. 2021)—and also east through New Caledonia ( Risbec 1928, 1953). Some were found in Japan —Zamami Island ( Ono 2004) and Amami Island ( Nakano 2019a)—and possibly in Malaysia ( Coleman 2008) as well.

Remarks. The specimen WAM S112548 from New South Wales agrees with the original description of Chromodoris variata by Risbec (1928) from New Caledonia in that it has dorsal yellow dots, multiple violet spots, and red rhinophores. The gill is almost translucent with a slight red tinge; the color varies from red to faintly reddish in the Port Stephens area. The specimen differs a little from Risbec’s (1928, 1953) descriptions in that each submarginal violet spot is bordered with a lighter violet-blue color, a condition not described and illustrated by Risbec (1928, 1953). It also differs by not having a yellow crescent on each submarginal violet spot; however, specimens that do have these yellow crescents also occur in the population (e.g., Foster et al. 2021). Rudman (1987) also described variation in the dorsal dots. He noted that the color of the dots could range from yellow to golden brown, in size from small to quite large blotches; we also note that some of these blotches are more indicative of background color rather than coalesced smaller brown dots. Comparison with topotype material from New Caledonia will be necessary to confirm the species name application and the taxonomic status of these chromodorids with/without yellow crescents in New South Wales. Specimens from Malaysia have some differences in pigmentation and require further molecular characterization to be determined as G. cf. variatus or G. aureopurpureus .

Figures

Fig. 2. Goniobranchus aureopurpureus (Collingwood, 1881), ICHUM 6270 (A, B), and G. cf. variatus (Risbec, 1928), WAM S112548 (C). A, Dorsal view in living state; B, scanning electron micrograph showing lateral part of the radula; C, underwater photograph, dorsal view.