Nembrotha cristata Bergh, 1877next section
Nembrotha cristata Bergh, 1877a: 458; Bergh, 1905: 194, pl. 18, figs 4-8; Yonow, 1994: 108, figs 6E, 8D; Pola et al., 2008: 153, figs 1G, 4B, 6.
Material.— RMNH.MOL.131697, RBE Stn 44, Latuhalat, Leitimur, 9 m depth “lowest littoral,” 12.xii.1990, leg. W. Kolvoort, 17 × 7 × 9 mm pres., photos M. Lavaleye 51-31/33, 303-4, and W. Kolvoort; Bunaken, Manado, North Sulawesi, < 15 m depth, xi.1990, one individual, photos only H. Debelius; Derawan, East Borneo, iv.1997, one individual, photos only J. Hinterkircher.
Non-Indonesian material.— Bohol, Philippines, ix.2003, photos of one individual, J. Hinterkircher.
Fig. 1. Nembrotha lineolata. Radular teeth of 20 mm specimen. Scale bar 50 µm.Trevelyana cristata Bergh, 1874: pl. 33, fig. 6.
Remarks.— Nembrotha cristata resembles N. kubaryana (see below) by its velvety black dorsum and green pustules on the sides. The rhinophore sheaths, gill rachides and leaflets, anal papilla, and the edge of the foot were all green (pl. 1 fig. 1), differing from N. kubaryana by lacking any orange pigmentation. It also differs from the green and black N. milleri (p. 910) in having a black ground colour instead of green. Bergh described and illustrated this species from a single specimen collected in the Philippines. The species is essentially West Pacific in distribution, but two individual records exist from the east (Western Australia, Wells & Bryce, 1993) and west (Maldives, Yonow, 1994) sides of the Indian Ocean.
Nembrotha kubaryana Bergh, 1877
Trevelyana nigerrima Bergh, 1874: pl. 33, fig. 5.
Nembrotha kubaryana Bergh, 1877a: 454; Bergh, 1881a: pl. G, fig. 16; Bergh, 1881b: 659; Bergh, 1905: 197, pl. 5, fig. 13; Yonow & Hayward, 1991: 11, figs 7E, 12C; Gosliner et al., 2008: 112.
Nembrotha nigerrima Bergh, 1877a: 451; Bergh, 1905: 196, pl. 18, figs 13, 14; Pola et al., 2008: 147, figs 1A-F, 2, 3, 4A, 5.
Material.— RMNH.MOL.131687, RBE Stn 17, 2 km SE of Pombo, Ambon, 16.xi.1990, “lowest littoral,” leg. A.F. de Jong, 15 × 10 mm pres., photos M. Lavaleye 14/33-34; RMNH.MOL.131686, Manado, N. Sulawesi, 8-15 m depth, x.1990, leg. H. Debelius, 31 × 10 × 16 mm pres.; Derawan, East Borneo, iv.1997, one individual 25 mm in length, photos only J. Hinterkircher; RMNH.MOL.131688, Nusa Ela, Pulau Tiga, < 4 m depth, 25.xi.1997, leg. H. Strack, 20 × 10 mm pres.; Indonesia, one individual, photos only J. Hinterkircher.
Non-Indonesian material.— Bohol, Philippines, ix.2003, photos of one individual, J. Hinterkircher.
Description.— Nembrotha kubaryana is recognized by its velvety black dorsum and sides covered in green pustules, which may be separate or may coalesce into longitudinal rows. The rhinophores, rhinophore sheaths, oral tentacles, the tip of the foot and the foot margin were all bright orange (pl. 1 fig. 2). In some individuals the rhinophore sheath can be green (pl. 1 fig. 3). The gills are usually green but may be suffused with orange pigment in some specimens.
Remarks.— This species has a West Pacific distribution, and has been recorded as far east as Western Australia (Wells & Bryce, 1993: 83, fig. 92). There is one published record from Mauritius in the western Indian Ocean (Yonow & Hayward, 1991) but NudiPixel and SeaSlugForum have several photographs from Mauritius and East Africa. Yonow & Hayward (1991: 12) realised that N. kubaryana Bergh, 1877, and N. nigerrima Bergh, 1877, constituted the same species and selected Nembrotha kubaryana as the valid name. In this choice, Yonow & Hayward (1991) deliberately acted as First Reviser in the sense of Article 24.2.2 of the International Code of Zoological Nomenclature (ICZN, 1999; not 2000 as in Pola et al., 2008). Although both names were first formally published in the same work (Bergh, 1877a), kubaryana was selected because it is the better known and most frequently used name in the current literature; in fact, Pola et al. (2008) use Bergh’s illustration of kubaryana (1905, pl. V fig. 13) as the original drawing for nigerrima. Pola et al. (op. cit.) agreed with the synonymy but then attempted to justify nigerrima as a nomen protectum under Article 23.9.1 of the Code. In doing so, they overlooked the previous actions by Yonow & Hayward (op. cit.); Article 23.9.1 of the code does not apply because both names have been in use since 1899 and are therefore available. It is now generally accepted that N. kubaryana is the correct name for this species (Gosliner, 2008).
Nembrotha lineolata Bergh, 1905
Nembrotha lineolata Bergh, 1905: 199, pl. 2 figs 10, 11, pl. 18 figs 15-18; Eales, 1938: 95, figs 13-16; Marshall & Willan, 1999: 52, fig. 79; Yonow et al., 2002: 838, figs 2e, 4a, 5, 6A; Pola et al., 2008: 155, figs 4C, 7, 8.
Nembrotha cf. lineolata Yonow et al., 2002: 841, figs 4b, 6B.
Material.— RMNH.MOL.131685, RBE Stn 16, W side of Pombo, Ambon, 5 m depth, 15-17.xi.1990, “on rubble reef,” leg. A. Fortuin, 10 × 6 mm pres., photos M. Lavaleye 22/21-22; RMNH.MOL.131683, RBE Stn 27, Hutumuri, Leitimur, 15 m depth, 26-27.xi.1990, leg. K. van Egmond, 20 × 7 mm pres., photos M. Lavaleye 34/4-7 (retains brown bands); RMNH.MOL.131684, RBE Stn 39, S Larike, Hitu, 8-9.xii.1990, leg. W. Kolvoort, 18 × 5 mm pres., photos M. Lavaleye 49/32-35 and W. Kolvoort (retains brown bands, gills and rhinophores extended).
Non-Indonesian material.— Bohol, Philippines, ix.2003, photos of one individual, J. Hinterkircher; Bohol, Philippines, iii.2004, photos of one individual, J. Hinterkircher.
Fig. 5. Gymnodoris aurita. Selected radular teeth of 35 mm specimen: left and right first lateral, laterals 2-4, 25-27, and 31-33, photographed from near the new edge. Scale bar 50 µm.
Description.— All Ambonese specimens were cream with numerous narrow longitudinal brown lines and a brown band on the front of the head (pl. 1 fig. 4); in the third specimen these lines were almost black (pl. 1 fig. 5). There was a purple band (shading to brown in two specimens) on the edge of the rhinophoral sheaths, gill bases, and tip of the foot; this band was followed by a yellow band on the gills and the rhinophoral sheaths. The foot margin was blue with a distinct submarginal yellow line. The three large gills and the rhinophores were reddish-brown in two specimens and reddish in the third. The radula of the largest specimen was examined, and its formula is > 21 × 22.214.171.124.8. It is regular (fig. 1) and the rachidian is almost square, barely wider than long, and broadest in the middle, narrowing towards the base. The rachidian bears five denticles, the 3rd and 4th of which are joined at their bases.
Remarks.— This species appears to be one of the most variably coloured species of Nembrotha throughout its range in the tropical Indo-West Pacific, as evidenced by the literature, and specimens and photographs studied here. The brown lines may be thick or thin, but there is always a dual-tone banding on the margins of the foot, rhinophores, and gills. Bergh (1905) described this species from Selayer, Indonesia, and it has been photographed from many locations in Indonesia (e.g. Debelius & Kuiter, 2007; Gosliner et al., 2008; NudiPixel; SeaSlugForum). Nembrotha lineolata has been rarely recorded from the Indian Ocean, and Nembrotha cf. lineolata from Chagos (Yonow et al., 2002) is here assigned to this species, on the basis that the radula is frequently deformed and irregular in the species. The radula of Eales’ specimen (1938) has many fewer rows than in other descriptions but the shapes of the teeth are similar in all illustrations listed above. Eales’ specimen measured 22 mm in length and had a radula formula of 14 × 126.96.36.199.7, shorter than that of the 20 mm specimen from Leitimur. The largest Chagos specimen (65 mm) had a formula 36 × 188.8.131.52.6; the rather irregular radulae of the Chagos specimens clearly demonstrate that the teeth are just as variable intra-specifically in shape as is the external colour pattern, although the joining of the bases of the 3rd and 4th denticles appears to be a constant feature.
Nembrotha milleri Gosliner & Behrens, 1997
Nembrotha milleri Gosliner & Behrens, 1997: 296, figs 7-9; Pola et al., 2008: 172, figs 14G, 16C, 18.
Material.— Derawan, East Borneo, iv.1997, one individual 60 mm in length, photo only J. Hinterkircher.
Non-Indonesian material.— Bohol, Philippines, iii.2004, photos of one individual, J. Hinterkircher.
Remarks.— These records of N. milleri are unfortunately based only on photographs: they were dark velvety green with longitudinal black creases along the body which also ran up the gill bases. The rhinophore sheaths and gills were green basally, but with green-edged black lamellae. A Periclimenes sp. shrimp was noted living within the gills (pl. 1 fig. 6). Tonozuka (2003) also provides a photo taken south of Sulawesi showing two Periclimenes sp. on N. milleri. No other species is similar: N. cristata (p. 907) is also green and black but the ground colour is black, not green as in N. milleri. Nembrotha kubaryana (p. 908), which can have a green linear pattern on black but is more usually spotted, has brighter green markings and additional bright orange margins.
Nembrotha spec. nov.
Nembrotha rutilans Debelius & Kuiter, 2007: 62, lowest left photo only (non rutilans Pruvot-Fol, 1931).
Nembrotha chamberlaini Gosliner et al., 2008: 116, right photo only (non chamberlaini Gosliner & Behrens, 1997).
Material.— RMNH.MOL.131696, Bunaken, Manado, North Sulawesi, 5-15 m depth, xi.1990, 20 × 10 mm pres.; leg. and photos H. Debelius.
Description.— The single specimen is well preserved, and the brown patches remain on the dorsum. The photographs depict two large patches of chocolate brown in front of and behind the gills (pl. 2 fig. 1), extending the length and breadth of the body and meeting on either side of the gills; there was no gold line surrounding the brown dorsal patches. The body colour was opaque white, with a faint yellow line only along the violet margin of the foot. The three large gills were red distally and white proximally: the common basal stump had an ochre patch extending onto the notum. Other ochre patches were also present at the base of the rhinophores and near the tip of the tail. None of these had a gold border although they had golden flecks within. The rhinophores had dark reddish-brown lamellae, a white tip, and a paler stalk. Ventrally, the foot corners, head, oral tentacles, and tip of the tail were violet (pl. 2 fig. 2).
In the preserved specimen, the blue line on the head and oral tentacles is still present as a dense band and internally, there is a blue band remaining on the oral tube. The radula was examined and has the formula > 13 × 184.108.40.206.7-8. It is deformed, missing all but one marginal tooth on the left side. The rachidian bears five regular denticles on the cusp and is broadest below these, tapering to the slightly rounded base (fig. 2). Unlike those of Nembrotha lineolata (p. 909), the denticles are approximately equal in size and are not joined at their bases. The rachidian teeth are broader than they are high. The first lateral is typical for the genus, very large with a broad base and hooked cusp; the marginal teeth are small rectilinear plates decreasing in size along the row.
Remarks.— The most similar species is Nembrotha chamberlaini Gosliner & Behrens, 1997, originally described and subsequently recorded only from the Philippines (Pola et al., 2008); two individuals were photographed in Bohol, Philippines (pl. 2 fig. 3; pers. comm. J. Hinterkircher, ix.2003 and iii.2004). There are slight variations in the tone of colours but the pattern remains very constant: N. chamberlaini has uniformly red gills and rhinophores with a contiguous intense red patch at the base of each, and a red patch is also present at the end of the tail; these red patches often have a yellow ring around them. The large chocolate brown dorsal patch is also surrounded by a golden yellow line. In the new species described here (and many other photographs available on NudiPixel and SeaSlugForum) the red patches are replaced by ochre and the gills and rhinophores are bicoloured red and white, not uniformly deep red. The large brown dorsal patch of N. chamberlaini is edged in yellow in the original description and other photographs but not in this species. The radula of N. chamberlaini is similar, perhaps longer, and the rachidian of a 62 mm preserved specimen was more asymmetrical than in this small 20 mm preserved specimen.
Photographs of this species on the internet are now filed under Nembrotha purpureolineata O’Donoghue, 1924, because most were originally recognised as different and assigned to N. rutilans (Pruvot-Fol, 1931). When N. rutilans was synonymised with N. purpureolineata by Pola et al. (2008), the photos were simply reassigned despite the differences evidenced by their original designations. (The synonymy of rutilans with livingstonei Allan, 1933, in Gosliner et al. (2008) is erroneous. However, this error serves the point that these forms can be separated, and have been so in the past.) Nembrotha purpureolineata is indeed similar but never has red patches on the dorsum at the bases of the gills and rhinophores nor on the tip of the tail; additionally, it is only found in Australia. Its brown lines may merge to form smaller and more striped patches. If anything, purpureolineata is most easily confused with N. lineolata (p. 909), which has brown lines on the dorsum almost identical to the thin-lined forms of N. purpureolineata. However, despite the lack of external and internal differences, Pola et al. (2008) maintain these two as distinct species. This specimen from Sulawesi is identified as Nembrotha spec. nov. because of its pattern of ochre patches on the mantle at the bases of the bicoloured gills and rhinophores and on the tail, not surrounded by a gold line. This is a constant feature, as evidenced by many photographs from Indonesia on NudiPixel, MedSlugs, and the SeaSlugForum depicting animals identical in colour pattern to Nembrotha spec. nov.; the species shows no variation in colour pattern towards either chamberlaini or purpureolineata. Significantly, all individuals appear to have been photographed only in Indonesian waters.
Both chamberlaini and purpureolineata are confused, but if the presence or absence of the three red patches is used to distinguish them, they separate neatly into three species. Nembrotha purpureolineata has a streakier pattern with pale bases to the bicoloured gills and rhinophores, and is recorded only from northern Australia. Nembrotha chamberlaini has large brown patches surrounded by gold, uniformly red gills and rhinophores, red dorsal patches at the bases of the gills and rhinophores, and is recorded from the Philippines, Indonesia, and Malaysia. Nembrotha spec. nov. is ochre with bicoloured rhinophores and gills, no red patches, and recorded only from Indonesia. It is more prudent at this stage to retain the three clearly distinguishable species, based on external colouration and geographical distribution, than to combine them into one widely distributed and highly variable species (with four forms since we must also include N. lineolata). It has been stated by most authors that the only consistent feature separating species of Nembrotha is colour pattern; if this gold patterned species is assigned to N. chamberlaini, then all species will have to be re-assessed with the same criteria: the end result would be very few species with many colour forms.
Roboastra gracilis (Bergh, 1877)
Nembrotha gracilis Bergh, 1877a: 458, pl. 56, figs 11-17.
Nembrotha rubropapulosa Bergh, 1905: 198, pl. 5 fig. 14 (Selayer, Indonesia).
Nembrotha ? rubroocellata Bergh, 1905: 201, pl. 4 fig. 14 (Timor, Indonesia) syn. nov.
Roboastra gracilis Hamatani & Baba, 1976: 136, figs 1A, 2A-C; Yonow, 1994: 109, fig. 6F; Marshall & Willan, 1999: 55, fig. 85; Pola et al., 2005: 168, figs 1-4a; Gosliner et al., 2008: 112.
Material.— RMNH.MOL.131720, Bunaken, Manado, North Sulawesi, 5-15 m depth, xi.1990, 9 × 3 mm pres., leg and photos H. Debelius (also in Debelius & Kuiter, 2007: 65, middle lower photo).
Non-Indonesian material.— Bohol, Philippines, xi.2005, photos of one individual, J. Hinterkircher.
Remarks.— This species is recognized by its small size combined with a black body having few longitudinal orange stripes, and watery blue or green gills and rhinophores (pl. 2 fig. 4). The Pacific form differs slightly from the Indian Ocean one: the orange stripes are consistently wider in the Pacific Ocean specimens, and there is more colour variation, as evidenced by the three names Bergh gave it (see synonymy above). Bergh (1905) recorded N. ? rubroocellata from Timor, Indonesia, with darker rhinophores, gills and oral tentacles; an individual virtually identical to this painting was photographed in the Philippines (pers. comm. J. Hinterkircher, see pl. 2 fig. 5). Another black species with orange stripes, Roboastra luteolineata (Baba, 1936), occurs in Japan and Australia but has not been recorded this far west. It is much larger, growing up to 70 mm, has many more yellow lines, and five bipinnate (Hamatani & Baba, 1976) or tripinnate (Pola et al., 2005) gills.