Revision of the Indo-Pacific genus Nembrotha (Nudibranchia: Dorididae: Polyceridae), with a description of two new species

Anatomical examination of new material collected from the Indo-Pacific and the review of several collections from around the world allows for the revision of the genus Nembrotha Bergh, 1877. Two new species, Nembrotha rosannulata n. sp. and Nembrotha aurea n. sp., are described. The oldest available name for the genus is Nembrotha nigerrima Bergh, 1877, which was subsequently designated as the type species by O’Donoghue, 1924. The study of the original type material of N. nigerrima confirmed that it is a senior synonym of another name introduced subsequently, Nembrotha kubaryana Bergh, 1877, the name most commonly used for this species. However, according to the provisions of the International Code of Zoological Nomenclature (Article 23.9.1), there is no reason to invalidate the senior name Nembrotha nigerrima, since it has been used as valid after 1899. Nembrotha cristata Bergh, 1877, N. lineolata Bergh, 1905, N. purpureolineata O’Donoghue, 1924, N. livingstonei Allan, 1933, N. megalocera Yonow, 1990 and N. guttata Yonow, 1993, which are poorly known, are redescribed. Nembrotha rutilans (Pruvot-Fol, 1931) is synonymised with N. purpureolineata. Nembrotha yonowae Goethel and Debelius, 1992 is synonymised with N. guttata. The radulae of Nembrotha milleri Gosliner and Behrens, 1997 and N. mullineri Gosliner and Behrens, 1997 are redescribed.


INTRODUCTION
A number of species belonging to the genus Nembrotha have been described from the tropical Indo-Pacific (Table 1).Most of the nominal species were distinguished when originally introduced by differences in the colour pattern.Eliot (1904) described N. caerulea from East Africa and suggested that it was highly probable that all the common species of Nembrotha (N.nigerrima, N. kubaryana and N. cristata) were varieties of the same species.Since then, ten new species of Nembrotha have been introduced.Bergh (1905) described Nembrotha lineolata from Indonesia.O'Donoghue (1924) designated N. nigerrima as the type species of the genus, but at the same time he described a new species, namely N. purpureolineata from western Australia.Nembrotha rutilans, unfortunately named as Kentiella rutilans by Pruvot-Fol (1931) on the basis of a painting in a book by William Saville-Kent (1893), can only be identified from a colour painting.Allan (1933) justified the introduction of N. livingstonei from western Australia, based on the presence of a conspicuous star-shaped patch of pale yellow extending down to the anterior frontal margin.Characteristic features of the genus Nembrotha (after Burn, 1967) are the limaciform form, the rectangular rachidian teeth with 4 to 5 denticles along the upper margin, the lateral teeth with a simple cusp and 6 to 14 marginal plates.The buccal collar is weak, and the labial armature is very weak or absent.The prostate gland is large, racemose and spread over the bursa copulatrix.Since Burn's publication, N. megalocera Yonow, 1990 from the Red Sea, N. yonowae Goethel andDebelius, 1992 andN. guttata Yonow, 1993 from the Maldive Islands and N. chamberlaini, N. milleri and N. mullineri (Gosliner and Behrens, 1997) from the Indo-Pacific have been described.Moreover, a recent study on the Phylogenetic relationships of Nembrothinae based on molecular and morphological data (Pola et al., 2007) includes all the available nominal species of Nembrotha to date.In the present study, we review the systematics of the genus and propose a revised taxonomy based on the study of specimens collected from different localities around the Indo-Pacific, the geographical range of the genus.We also describe two additional species of Nembrotha, which are included in the above-mentioned phylogenetic analysis as Nembrotha sp. 3 (N.aurea n. sp.) and Nembrotha sp. 4 (N.rosannulata n. sp.).examination.The internal features were examined using a dissecting microscope with a camera lucida.Special attention was paid to the morphology of the reproductive system, including the penial hooks.The penis was critical point dried for scanning electron microscopy.The buccal mass was dissolved in 10% sodium hydroxide until the radula was isolated from the surrounding tissue.The radula was then rinsed in water, dried and mounted for examination by scanning electron microscopy.The external and internal anatomy of previously well-described species are not repeated in this paper in order to reduce the length of the manuscript.Also, since the reproductive system of the different species is very similar and they are well illustrated, only the reproductive system of the first species described and those of the new species are described in detail in order to reduce the descriptions and avoid being repetitive.Differences among reproductive systems are noted.In Figures 4 and 16, the prostate is shown positioned to the side.References to the original descriptions are made when possible.
Diagnosis.The body is limaciform, with dorsum smooth or covered with pustules.Head rounded, without frontal or velar processes and with two large oral tentacles with a depression at the centre of each.Gill bi-or tripinnate and not retractile.Rachidian teeth with 4-5 denticles along the upper margin, lateral teeth elongate, with two cusps, the inner cusp simple.Marginal plates 6-14.A labial cuticle is present, lacking armature.The prostate gland is large, racemose and spread over the bursa copulatrix.The penis is armed.A vaginal gland is absent.
remarks.The genus Nembrotha was introduced by Bergh, 1877 with six new species.These species were easily divided into different groups according to the shape of the radula but Bergh never gave them different generic names.In 1924, O'Donoghue stated that there was a possibility that the generic name Nembrotha Bergh, 1877 would have to be replaced by angasiella Angas and Cross, 1864, since the form described by the latter was very similar to those in Bergh's genus. However, O'Donoghue (1924) could not confirm this possibility until he obtained further specimens for closer examination.Some years later, Marcus (1958) in his discussion of tambja divae [Nembrotha], thought that the genus angasiella must not be substituted for Nembrotha because the species angasiella edwardsi Angas, 1864 was described as spinous while the species of Nembrotha were smooth.Burn (1967) separated the species formerly attributed to Nembrotha into three different genera (Nembrotha Bergh, 1877, roboastra Bergh, 1877and tambja Burn, 1962) based on radular and genital differences and assigned them to a new subfamily, Nembrothinae, family Polyceridae.Prior to this, the three genera were included in the family Gymnodorididae (Odhner, 1941;Marcus, 1958;Marcus and Marcus, 1964), or the subfamily Gymnodoridinae (Macnae, 1958).The phylogenetic analysis performed by Pola et al. (2007) supports the separation made by Burn (1967) of Nembrotha from roboastra and tambja, based on morphological characters.This analysis supports the existence of two clades in Nembrotha, one formed by the so-called "spotted" Nembrotha and other by the so-called "lined" Nembrotha.Bergh, 1877 (Figs. 1A-F, 2-3, 4A, 5) Nembrotha nigerrima Bergh, 1877: 451, pl. 32, Fig. 5. Nembrotha kubaryana Bergh, 1877: 454. material   external morphology.The body is elongate and limaciform but robust and widest at the gill.The posterior end of the foot is long and pointed (Figs.1A-F).The head is rounded.The adult living animals may grow up to 100 mm in total length.The body wall is highly muscularised.The notum is covered with a series of longitudinally oriented creases or wrinkles and pustules (or spots) scattered on the notum and both sides of the body (Figs.1A-F).A notal margin is absent.There is a pair of large and conical, perfoliate rhinophores, which are completely retractile into their elongate rhinophoral sheaths.The oral tentacles are well-developed, circular in shape with a depression at the centre of each.There are five tripinnate, non-retractile well-developed branchial leaves.The two posterior leaves of each side share a common base.The anus is situated in the centre of the branchial circle on elevated elongate papillae.The genital pore opens on the right side, midway between the rhinophores and the anterior portion of the gill.

Nembrotha nigerrima
The general colour of the living animals is highly variable (Figs.1A-F).The ground colour is black with green pustules scattered randomly on the notum and both sides of the body.There are also some small orange pustules usually located at the end of the foot and on the frontal edge.In some specimens, the green pustules are joined forming green longitudinal ridges over the entire body (Figs.1A,D,E).Those pustules around the frontal edge also tend to form a ridge.The edge of the foot has a bright orange stripe, as well as the rhinophoral sheaths and the oral tentacles.The rhinophores are black with orange pigmentation on the upper lamellae.The gill branches are orange, green or may have both colours at the same time (Figs.1A-F).In some specimens, all the green markings are orange (Fig. 1F).
The reproductive system is triaulic (Fig. 4A).The hermaphroditic duct is long.It expands into an elongate and convoluted ampulla.The postampullary duct branches into the prostatic portion of the vas deferens and the short oviduct that connects to the female glands.The prostatic portion of the vas deferens is very large and consists of a spherical mass, which appears to be formed by a dense network of interconnecting tubules entirely surrounding the bursa copulatrix.The distal end of the prostatic mass connects to an elongate and convoluted vas deferens.The vas deferens opens into a common atrium with the vagina but without a strongly differentiated muscular ejaculatory portion.The penis is armed with chitinous penial spines.Two different kinds of spines can be differentiated based on their size and shape (Fig. 5A).The basal spines are short and curved, all of them supported by the same rachis, and they constitute the eighteen first rows of spines (Fig. 5B).The remaining spines are longer and hooked, but it is not clear whether they are supported by the same rachis (Figs.5C,D).The vagina is wide, long and straight.At its proximal end, it connects to the rounded bursa copulatrix, which, in situ, is entirely surrounded by the prostate.From the bursa copulatrix leads another duct that connects to the pyriform seminal receptacle and the female glands via a long, narrow uterine duct.The vagina is separated from the vas deferens along its entire length.There is no vaginal gland.In Figure 4A, the prostate is shown positioned to the side.19991127).Scale bar = 1 mm.Abbreviations: am, ampulla; bc, bursa copulatrix; fglm, female gland mass; ga, genital atrium; hd, hermaphrodite duct; pr, prostate; rs, receptaculum seminis, ud, uterine duct; va, vagina; vd, vas deferens.
description of this species is very complete and the external colouration was depicted according to the living animal (Fig. 1A).In the same paper, Bergh described N. kubaryana also from Palau but never gave a description of the specimen.In the short comment about this new species he suggested that N. kubaryana could be only a variety of N. nigerrima but distinguished both species according to differences in colour, the number of marginal plates, small differences in the shape of the penial spines and the receptaculum seminis.However, all these features are very variable between specimens of Nembrotha, so N. kubaryana is a junior synonym of N. nigerrima.Similar conclusions have already been presented by Yonow and Hayward (1991), who formally synonymised both names, by Baba (unpublished data) and by Debelius (1996), but they never supported their conclusion with anatomical studies.
All modern authors have been using the name Nembrotha kubaryana for specimens of N. nigerrima since Yonow synonymised both names in 1990.Thus, Yonow (1990) considered N. nigerrima as a synonym of N. kubaryana.According to the international Code of Zoological Nomenclature (ICZN 2000), if a senior synonym has not been used as a valid name after 1899 and its junior synonym has been used for the same species in at least 25 papers, published by at least 10 authors in the immediately preceding 50 years and encompassing a span not less than 10 years, the usage of the junior synonym must be maintained (Article 23.9.1).Nevertheless, in this case, the name N. nigerrima has been used as a valid name after 1899 and there is therefore no reason to invalidate the senior name N. nigerrima.Thus, all names introduced subsequently must be synonymised with N. nigerrima, which is in addition the type species of the genus.Rudman's seaslugforum (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) and an increasing number of web pages and field guides, provide a large number of photographs showing specimens of Nembrotha nigerrima with remarkable differences in colouration and pattern of lines and pustules.(Debelius, 1996;Coleman, 2001;Wells and Bryce, 1993;Tonozuka, 2003; www.philippine-seaslugs.com; www.seaslugforum.net;http://www.philippine-sea-slugs.com/DORIDINA/Nembrotha_liv-ingstonei_04.htm).
Geographic range.This species, originally described from Palau and Cebu Islands, is also known from Indonesia (Debelius, 1996;Coleman, 2001;Tonozuka, 2003;Debelius and Kuiter, 2007), Mauritius Islands (Yonow and Hayward, 1991;Debelius and Kuiter, 2007), Great Barrier Reef, Western Australia (Willan and Coleman, 1984;Wells and Bryce, 1993;Coleman, 1989;2001;Debelius and Kuiter, 2007), Kerama Islands (Ono, 1999), Ryukyu Islands (Ono, 2004), Papua New Guinea, Marshal Island (present study), Malaysia and Solomon Island (http://www.seaslugforum.net/factsheet.cfm?base=nembkuba).Bergh, 1877 (Figs. 1G, 4B, 6) Nembrotha cristata Bergh, 1877: 458, pl. 33 external morphology.The body is firm and limaciform with a linear and pointed posterior end of the foot.The head is rounded.The mantle is reduced and indistinct (Fig. 1G).The preserved specimens are up to 40 mm.The living animals' measure up to 120 mm with the body surface covered with roundish, elongate and irregularly-shaped, hardly-elevated pustules or spots (Fig. 1G).On the front edge, the tubercles extend around the head suggesting a wide mantle margin.There is a pair of perfoliate rhinophores that are completely retractile into their rhinophoral sheaths, with 25 lamellae.The oral tentacles are short and circular in shape with a depres-sion at the centre of each.There are five non-retractile, strongly developed multipinnate gill branches.The two posterior gill branches of each side share a common base.The anus is situated between the gill branches on elevated papillae just behind the kidney opening.The genital pore opens on the right side, midway between the rhinophores and the anterior portion of the gill.

Nembrotha cristata
The ground body colour is black with green tubercles (Fig. 1G).The rhinophores are black with a green tip.The outer branchial surface, the inner rachis of each gill branch (except the base), the pinnae, the rhinophoral sheaths and the edge of the oral tentacles are also green.The edge of the foot is bordered with a green band.
anatomy.Nembrotha cristata shares the same general internal anatomy as other Nembrotha species (Fig. 2).The anterior digestive tract begins with a long but thin oral tube that continues into the buccal mass.Two long wide salivary glands connect to the buccal bulb at both sides of the oesophageal junction.The thin chitinous labial cuticle is corrugated without distinct armature or rodlets.The radular formulae are: 65 mm specimen, 27 x 9.1.1.1.9(MNCN 15.05/46714), 88 mm specimen, 24 x 9.1.1.1.9(MNCN 15.05/46715), 25 mm specimens, and 23 x 10-9.1.1.1.9-10(CASIZ 076014) (Figs.6A,B).The rachidian teeth are broad and rectangular with five asymmetrically arranged triangular denticles almost similar in size.The two inner denticles of the right half of the rachidian are joined at the base (Fig. 6B).The inner laterals are well developed; they are larger and longer than the outer ones with a rectangular base and two cusps, an elongate terminal cusp and a shorter more basal one.The outer lateral teeth are rectangular plates, becoming smaller near the margin.The innermost one bears an upper cusp while the remaining teeth lack cusps or dentition (Fig. 6A).
The reproductive system is triaulic (Fig. 4B).The hermaphroditic duct is short and narrow.It expands into the ampulla.The long straight postampullary duct divides into a short oviduct and a wide prostatic portion of the vas deferens.The prostatic segment is very large and consists of a spherical mass.The distal end of the prostatic mass branches into a narrow, elongate and highly convoluted vas deferens.The distal end of the vas deferens widens into a muscular ejaculatory portion, which opens into the genital atrium.The chitinous penial spines are numerous and they are arranged in longitudinal lines.
They can be differentiated into three different kinds of spines based on their size and shape (Figs.6C-F).The basal spines are large, elongate and curved.They constitute the first three or four rows of spines (Fig. 6D).The spines immediately after these are much smaller and hooked (Figs.6E).The remaining spines are also hooked and slightly more elongate than the second group but shorter than the basal spines (Fig. 6F).The vagina is wide, long and slightly convoluted.At its proximal end, the vagina connects to the rounded, thin-walled bursa copulatrix, which, in situ, is entirely surrounded by the prostate.From the bursa copulatrix leads another duct that connects to the pyriform seminal receptacle and the female glands via a long, distally convoluted uterine duct.The vagina is separate from the vas deferens along its entire length.
remarks.Nembrotha cristata was described by Bergh (1877) from Semper's individual collected from the Philippine Sea.Semper illustrated this animal in living condition, but the animal was lost.Thus, the species is known only from the illustration.In 1905, Bergh collected 3 additional specimens from the reef at Tual, Niedrig-Kei Island.The smaller one was strongly contracted, and the other 2 specimens were similarly large (50 and 58 mm) and resembled each other.All the specimens dissected in this study identified as N. cristata perfectly match Bergh's description, though he described three gills instead of five.We assume that he counted the two lateral branches of each side as only one.Eliot (1904) described three specimens of N. cristata from the east coast of Zanzibar as very dark but brilliant green with black spots, and also narrow stripes of brighter and lighter green.At the end of his description he stated that these specimens might be a variety of N. nigerrima.Yonow and Hayward (1991) rejected this idea and stated that Eliot's description was not applicable to either N. cristata or N. nigerrima.N. cristata differs mainly from N. nigerrima by the absence of any red or orange colouration.The features of the radula and the reproductive system are very similar in both species, but N. cristata has three well-differentiated types of penial spines while in N. nigerrima there appear to be only two types.Nembrotha cristata has been found feeding on the compound green ascidian eudistoma olivaceum (http://www.philippine-sea-slugs.com/DORIDI-NA/Nembrotha_cristata.htm;Willan and Coleman, 1984).
Geographic range.This species, originally described from the Philippines, is also known from Indonesia (Coleman, 2001;Houghton, 2002;Tonozuka, 2003: Debelius andKuiter, 2007), Malaysia, Solomon Island (www.seaslugforum.net/factsheet.cfm?base=nembcris), Papua New Guinea (present study;McNeil, 1999), Kerama Island (Ono, 1999), Ryukyu Islands (Ono, 2004), Maldivas (Debelius, 1996) and North Queensland and Western Australia (Willan and Coleman, 1984;Coleman, 2001;Debelius and Kuiter, 2007).Eliot, 1904 Nembrotha caerulea Eliot, 1904: 91 remarks.Eliot (1904) described Nembrotha caerulea from East Africa but it has not been reported since then.No notes on the living animal exist, except that it was blue and had apparently no red or green mottled colouration.Thus, Eliot described the species from freshly preserved specimens as being a fine bright indigo with the whole body marked with deep indigo spots.Although he stated that this species was closely allied to N. nigerrima, he distin-guished it by its colouration, the slightly projecting edges of the rhinophoral sheaths, the absence of labial armature and a different form of tentacles.Nevertheless, Baba (unpublished data) in his notes about roboastra, tambja and Nembrotha in Japan, described the general colouration of N. nigerrima and N. kubaryana as deep black ground colour with blue stripes and blue spots.These descriptions confirm that the descriptions of the colouration of preserved specimens could be wrong.Thus, in this paper, we consider N. caerulea as nomen dubium.

Nembrotha caerulea
Nembrotha lineolata Bergh, 1905 (Figs. 7, 4C, 8) Nembrotha lineolata Bergh, 1905: 199, pl. 2, Fig. 10. pl. 18, Fig. 15-18. Nembrotha lineolata var. Bergh, 1905: 200, pl. 2, Fig. 11.external morphology.The body is elongate and limaciform reaching, up to 70 mm in living adults.The posterior end of the foot is long and pointed.The head is rounded.The entire body surface has a pattern of longitudinal wrinkles (Fig. 7).The dorsum continues to the side of the body without a demarcating line or pallial edge.Externally the animals are characterised by the presence of longitudinal stripes that are sometimes broken.The number and distribu-tion of these stripes is variable (Fig. 7) and in many cases they merge to form the transverse bands found in some colour forms of this species (Fig. 7C).There is a pair of large conical, perfoliate rhinophores that bear 30-35 lamellae and are completely retractile into their elongate rhinophoral sheaths.The oral tentacles are thick and elongate with a depression at the centre of each one.There are three large multipinnate, nonretractile branchial leaves.The anus is mid-dorsal, located in the centre of the branchial circle on elevated elongate papillae.The genital pore opens on the right side, midway between the rhinophores and the anterior portion of the gill.
The ground colour of the body is yellowish white or cream white with numerous brown lines on the notum and both sides of the body (Fig. 7).In all cases, a thin dark line continues forward, anterior to the rhinophores.The margin of the foot is delineated by a blue to purple band, within which a yellow band is usually present.The oral tentacles are also blue or purple followed by a yellow band.The rhinophores are red.The rhinophoral sheaths are blue or purple above, sometimes with a green band below, and yellow at the base of the rachis.In some specimens from the Comoros Islands the rhinophores are yellow rather than red (Fig. 7B).There are two variable-sized translucent spots posterior to the rhinophores, through which the dermal eyes are visible.The branchial leaves are red or vermilion above, blue or purple below and yellow at the base.It is also pos- sible to find specimens without a trace of blue or purple colour in the gill (Figs.7B,D).
anatomy.Nembrotha lineolata shares the same general internal anatomy as other Nembrotha species (Fig. 2).The anterior digestive tract begins with a long and thin muscular oral tube that continues into the buccal mass.The buccal mass is smaller than the oral tube.There is a pair of large, wide salivary glands on the buccal mass, flanking the oesophagus.The labial cuticle forms a brown corrugated chitinous disk, usually devoid of rodlets but with a central and two lateral areas, in which in some specimens a weak armature is present.The radular formulae of some dissected specimens are: 33 and 25 mm specimens, 32 x 7.1.1.1.7,34 x 9.1.1.1.9(CASIZ 084291), 66 mm specimen, 32 x 8.1.1.1.8(MNCN 15.05/46724), 64 mm specimen, 28 x 6.1.1.1.6(MNCN 15.05/46725), 25 mm specimen, 23 x 5-6.1.1.1.6-5(MNHN-Paris).The rachidian teeth are broad and rectangular with five triangular denticles (Figs.8A,B).The two outer denticles are smaller than the inner ones.The two inner denticles on the right side are joined at the base.Thus, both denticles might be described as a single bifid denticle.The inner laterals are well developed; they are large and strongly hooked with two cusps (Fig. 8A).The outer lateral teeth are rectangular plates, from 5 to 8, which lack cusps or dentition and become smaller near the margin.There is a blood gland located above the genitalia, usually closer to the buccal mass than to the digestive gland.
The reproductive system is triaulic (Fig. 4C).The hermaphroditic duct is elongate and wide.It expands into a very long and highly convoluted ampulla.The prostatic portion of the vas deferens is very large.The distal end of the prostatic mass connects to an elongate, highly convoluted vas deferens that opens into a common atrium with the vagina but without a strongly differentiated muscular ejaculatory portion.The penis is armed with rows of curved, chitinous hooks except at the base (Figs.8C,D).The chitinous penial spines are numerous and similar in size and shape (Figs.8C,D).The vagina is very wide, long and convoluted.At its proximal end, the vagina connects to the rounded, thin-walled bursa copulatrix.In situ, the bursa copulatrix is entirely surrounded by the prostate.remarks.Nembrotha lineolata was described by Bergh (1905) from Indonesia based on three living specimens with a drawing of the largest specimen (60 mm in total length).The specimens described in that paper were yellowish white with many short brown longitudinal lines.The arrangement of the lines of those specimens appears to be nearly in agreement with the specimens described by Baba (1976) from Japan, with one exception.The lines in Baba's specimens are not as numerous on the upper surface of the body and they are longer and not as frequently interrupted in their length as in the type specimens.The colour of the rhinophores, gill and the edge of the foot were also similar.The radular formula of the specimen described by Bergh (1905) is 32-36 x 7.1.1.1.7,with 4-5 denticles on the upper edge of the rachidian teeth.The radular formula of Baba's specimens (30 to 50 mm in length) is 27 x 5-6.1.1.1.5-6with four denticles; the second denticle on the right side was bifid at the tip, which is also in agreement with the Indian Ocean specimen described by Eales (1938) and also with our specimens.The reproductive system of N. lineolata was not described by either Bergh (1905) or Baba (1976) but the anatomy was drawn by Eales (1938).
The dorsum continues to the side of the body without a line of demarcation or pallial edge.Externally the animals are characterised by the presence of a broad longitudinal band on the notum (Fig. 9).A thinner line passes round the front, anterior to the rhinophores, and back on each side of the notum.Behind the gill, these two lines converge and meet, about halfway between the gill and the posterior end, to form one line in the middle, which runs back to the end of the tail.Another line runs parallel to the edge of foot on each side.There is a pair of large conical, perfoliate rhinophores.The rhinophores, bearing 35-45 lamellae, are completely retractile into their elongate rhinophoral sheaths.The oral tentacles are thick, and elongate with a depression at the centre of each.There are from three to five large multipinnate, non-retractile branchial leaves.The anus is mid-dorsal, located in the centre of the branchial circle on an elevated elongate papilla.The genital pore opens on the right side, midway between the rhinophores and the anterior portion of the gill.
The ground colour of the body is yellowish white or cream white with a broad brown or black band on the notum and lines of the same colour on each side of the body (Fig. 9).The margin of the foot is delineated by a blue to purple band, usually with an internal submarginal yellow band.The oral tentacles are also blue or purple followed by a yellow band.The rhinophoral lamellae are red or vermillion with blue or purple tips.The base is pink.The rhinophoral sheaths are blue or purple above and yellow below.There are two, variable sized, translucent spots posterior to the rhinophores, through which the dermal eyes are visible.The branchial leaves are red or vermilion above, blue or purple below and yellow at the base.
The two inner denticles on one side are joined at the base, so both denticles might be described as having a single bifid denticle.The arrangement and length of these joined denticles is variable even between specimens with exactly the same external pattern (Figs.10C-F).The inner laterals are well developed; they are large and strongly hooked with two cusps.The outer lateral teeth are rectangular plates, from 7 to 10, which lack cusps or dentition and become smaller near the margin (Figs.10C,E).There is a blood gland located above the genitalia, usually closer to the buccal mass than to the digestive gland.
The reproductive system is triaulic (Fig. 4D).The hermaphroditic duct is elongate and wide.It expands into a very long and highly convoluted ampulla.The prostatic portion of the vas deferens is very large.The distal end of the prostatic mass connects to an elongate, thin and highly convoluted vas deferens.The vas deferens opens into a common atrium with the vagina but without a strongly differentiated muscular ejaculatory portion.The penis is armed with rows of curved, chitinous hooks except at the base (Figs.10G,H).The chitinous penial spines are numerous and they are similar in size and shape (Figs.10G-H).The vagina is wider than the vas deferens, long and convoluted.At its proximal end, the vagina connects to the rounded, thin-walled bursa copulatrix.
remarks.O'Donoghue (1924) described N. purpureolineata from a single preserved specimen 35 mm long collected from the Abrolhos Islands (Western Australia).He described the general colour as a dirty yellowish grey marked with pale brown lines and showed a drawing of the radula.Both the external pattern of lines and colours and the description of the radula from the type specimen perfectly match our recently collected material from the Abrolhos Islands (see also Wells and Bryce, 1993), which might have three or five gill leaves.The reproductive system of N. purpureolineata is described for the first time in this study.
In 1976, Baba described two additional specimens from Japan.The material examined in that paper had fewer lines than the type specimen of N. lineolata and they were rather thick, more similar to those of N. purpureolineata O'Donoghue (1924).The number of gill leaves (3) and the colouration were also very similar to the above descriptions but a large patch of orange was present in the middle of the back.This feature was used by Cervera et al. (1996) and Gosliner (pers. comm.) to conclude that the specimens depicted by Baba (1976) and Gosliner (1987) probably represent one or more undescribed species.However, Baba (1976) suggested that N. lineolata and N. purpureolineata could be synonyms.We are in agreement with Cervera et al. (1996) and consider that those specimens with a large orange patch in the middle of the back from Japan (Baba, 1976;Suzuki, 2000;Nakano, 2004), Indonesia (Debelius, 1996;Tonozuka, 2003), Western Australia (Coleman, 2001;Debelius and Kuiter, 2007), the Philippines and East Timor (Debelius and Kuiter, 2007) and South Africa (Gosliner, 1987;Fraser, 1999;King and Fraser, 2002) represent one or more undescribed species.
Nembrotha rutilans [Kentiella] was described from the Great Barrier Reef in 1931 by Pruvot-Fol from a painting done in 1892 (Fig. 9D) by an artist named William Saville-Kent.Pruvot-Fol did not describe the internal anatomy, and there are no type specimens to examine.The colouration as described by Pruvot-Fol is chocolate brown and pale yellow alternating with longitudinal stripes, and the pattern colour is identical to O'Donoghue's description (1924).In the present study we examined several specimens from Eastern and Western Australia with the same colour pattern as described above.Cervera et al. (1996) showed a comparative table of the features of the three colour forms discussed above.The synonymisation of N. rutilans with N. purpureolineata based on the lack of description of the internal anatomy is therefore justified.
Geographic range.This species, originally described from Western Australia (O'Donoghue, 1924;Willan and Coleman, 1984 as Nembrotha sp.; Coleman, 1989 as Nembrotha rutilans; Wells and Bryce, 1993;Coleman, 2001;present study), is also known from Eastern Australia (Pruvot-Fol, 1931; Rudman, 1999 (July 2)).Nembrotha livingstonei Allan, 1933 (Fig. 11A-D, 4E, 12) Nembrotha livingstonei Allan, 1933: 450, pl. 56, Fig. 15.external morphology.The body is elongate and limaciform, reaching up to 55 mm in length in living adults.The posterior end of the foot is long and pointed.The head is rounded.The entire body surface has a pattern of longitudinal wrinkles with small irregular spots scattered over the notum and both sides of the body (Figs.11A-D).In some specimens the spots are strongly marked, becoming pustules, while in other specimens the spots appear as irregular patches between the wrinkles.Externally, the animals are characterised by the presence of a cross-like mark between the rhinophores (Figs.11A-D).There is a pair of large conical, perfoliate rhinophores.The rhinophores, bearing 20-25 lamellae, are completely retractile into their elongate rhinophoral sheaths.The oral tentacles are thick and elongate with a depression at the centre of each.There are five strong multipinnate, non-retractile branchial leaves.The two posterior leaves of each side share a common base.The anus is mid-dorsal, located in the centre of the branchial circle.The genital pore opens on the right side, midway between the rhinophores and the anterior portion of the gill.
The general colour of the living animals is dark reddish brown with orange, reddish brown, green or white spots (Figs.11A-D).The rhinophores are orange-reddish with bluish-white pigmentation at their base.The rhinophorical sheaths are tipped in orange and their base is also white and blue.The conspicuous characteristic cross-like mark between the rhinophores is white to pale yellow in colour.The edge of the foot has a bright orange stripe, as do as the oral tentacles.The gill branches are reddish brown with orange-reddish tips.The base is white or pale yellow with electric blue above.The spots located at the end of the tail and those on the front edge are bright orange.
anatomy.Nembrotha livingstonei shares the same general internal anatomy as other Nembrotha species (Fig. 2).The anterior digestive tract begins with a muscular oral tube that continues into the buccal mass.The buccal mass is smaller than the oral tube.There is a pair of large, wide salivary glands on the buccal mass, flanking the oesophagus.The labial cuticle forms a brown corrugated chitinous disk, usually devoid of rodlets but with a central and two lateral areas (Fig. 12A).The radular formulae are: 52 mm specimen, 27 x 8-9.1.1.1.8-9(MNCN 15.05/46716), 42 mm specimen, 25 x 8.1.1.1.8(WAM S11555), and 20 mm specimen (preserved), 23 x 9.1.1.1.9((MNCN 15.05/46717) (Figs.12B-D).The shape of the rachidian teeth is shown in Figures 12B-D.There are five asymmetrically arranged triangular denticles along the upper margin.Two of the inner denticles might share a common base but their arrangement is variable.The innermost laterals are well developed; they are larger and longer than the outer ones with a rectangular base and two cusps, an elongate terminal cusp and a shorter more basal one (Figs.12B-D).The outer lateral teeth are rectangular plates, 8 to 9 in number, becoming smaller near the margin.The inner one bears an upper cusp while the remaining teeth lack cusps or dentition.There is a large blood gland located above the intestine.
The reproductive system is triaulic (Fig. 4E).The hermaphroditic duct is long.It expands into an elongate and convoluted ampulla.The prostatic portion of the vas deferens is very large.The distal end of the prostatic mass connects to an elongate, convoluted vas deferens.The vas deferens opens into a common atrium with the vagina but without a strongly differentiated muscular ejaculatory portion.The penis is armed with chitinous penial spines that can be distinguished into two different kinds of spines based on their size and shape (Figs.12E,F).The basal spines are short and curved, all of them supported by the same rachis, and they constitute approximately the first twenty rows of spines (Fig. 12G).The remaining spines are longer and hooked, but it is not clear whether they are supported by the same rachis (Figs.12E,F).In one of the dissected specimen from the Philippines (MNCN 15.05/46716) there appear to be three different types of penial spines, since at the base of the penis there are a few rows of large, curved spines followed by the two other types described above (Fig. 12H).The vagina is wide, long and straight in the specimens from the Philippines but it is convoluted in the specimen examined from Japan.At its proximal end, the vagina connects to the rounded bursa copulatrix, which, in situ, is entirely surrounded by the prostate.remarks.Nembrotha livingstonei was introduced by Allan (1933) based on the external colouration without any internal description.These features, as originally described, are consistent with the present material.The reproductive system is described in this paper for the first time.Nembrotha livingstonei is easily distinguishable from the remaining species of Nembrotha by the possession of the white crosslike mark between the rhinophores.However, some of the colour forms of N. livingstonei strongly resemble those of N. nigerrima (Fig. 11D).Externally, N. livingstonei shares the orange colouration of the rhinophoral sheaths, the oral tentacles, the spots of the frontal edge and the posterior end of the tail and the line bordering the foot with N. nigerrima.In some cases, the colouration of the gill circle is also similar.The pattern of wrinkles, lines and spots is also very similar in many specimens since the variability of both species is very high.With respect to the internal anatomy, N. livingstonei and N. nigerrima are the only two described species of the genus with two different types of penial spines.Moreover, in both species, the muscular ejaculatory portion of the vas deferens is not strongly developed and the vagina is not as wide as in the re-  maining species of the "spotted group" of Nembrotha.
The radular formulae and the teeth of N. livingstonei and N. nigerrima are also very similar.Figure 11D shows a specimen identified as N. livingstonei mating with a specimen of N. nigerrima.Rudman's seaslugforum (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) and several field guides (Coleman, 2001;Ono, 2004; and web pages (http://slugsite.us/bow/nudwk274.htm;http://www.philippine-sea-slugs.com/DORIDI-NA/Nembrotha_livingstonei.htm;http://rfbolland.com/okislugs/nemblivi.html)show different specimens that are variable in colour, but all of them are characterised by the presence of the conspicuous star-shaped patch between the rhinophores.N. livingstonei from Australia appears to have spots rather than lines.Slight differences in the reproductive system between different specimens do not show any consistent pattern and do not allow us to distinguish between specimens from the Philippines and Japan.All the specimens have an identical radular morphology.Debelius (1996) and Köhler (2001) show photographs of specimens from Tanzania and the Philippines, respectively, that they identified as N. livingstonei.However, we believe that they do not represent N. livingstonei.Debelius and Kuiter (2007) show a picture from South Africa identified as Nembrotha sp.4, which we believe is N. livingstonei.

Nembrotha megalocera
remarks.Nembrotha megalocera was originally described by Yonow (1990) from four specimens collected from the Red Sea.In that paper the author presented a description of the external morphology and colouration and provided a radular formula and a photo of one specimen.More recently, Cervera et al. (1996) provided a more detailed description of both the external and internal anatomy of this species based on one specimen (Fig. 11F) from Egypt (Red Sea) and compared N. megalocera with the closely related species N. lineolata, N. purpureolineata and N. rutilans.The specimens examined for the present study are in agreement with the description of both Yonow (1990) and Cervera et al. (1996).
Nembrotha megalocera looks very similar to N. purpureolineata and N. chamberlaini but differences in the external morphology such as the extremely long rhinophores and the constant number of gill leaves (3), as well as differences in colouration (black ground colour and orange sides with black markings) and subtle differences in the internal morphology such as a constantly square rachidian tooth, also allow us to distinguish it from the remaining species of the genera.Moreover, to date, N. megalocera has only been reported from the Red Sea, while the remainder of the several similarly coloured forms of N. lineolata are co-distributed throughout the tropical Indo-Pacific.Beautiful photographs of N. megalocera are shown in Debelius, 1996;Coleman, 2001; www.seaslugforum.net/factsheet.cfm?base=nembmega; www.medslugs.de/E/Ind-NW/Nembrotha_megalocera.htm;www.scuba-equipment-usa.com/marine/NOV04/Great_ Nembrotha(Nembrotha_megalocera).html; www.meerwasser-lexikon.de/de/71/1288/Nembrotha/megalocera.htm).
Geographic range.Thus far this beautiful species is only known from warm tropical waters of the Red Sea off northern Africa (Yonow, 1990;Debelius, 1996;Coleman, 2001;Debelius and Kuiter, 2007).Goethel and Debelius, 1992 (Figs. 14A-D, 15, 16A) Nembrotha yonowae Goethel and Debelius, 1992: 517, Fig. 20 external morphology.The body is elongate and limaciform but robust and widest at the gill.The posterior end of the foot is long and pointed (Figs.14A-C).The head is rounded.The mantle is small and indistinct.The adult living animals may grow up to 55 mm in total length with the body surface covered with randomly scattered pustules.The pustules around the frontal edge rise to form a ridge.There is a pair of perfoliate rhinophores that bear 25 lamellae and are completely retractile into their rhinophoral sheaths.The oral tentacles are short and circular in shape with a depression at the centre of each one.There are five non-retractile multipinnate gill branches.The two posterior gill branches of each side share a common base.The anus is situated between the gill branches on elevated papillae just behind the kidney opening.The genital pore opens on the right side, midway between the rhinophores and the anterior portion of the gill.

Nembrotha yonowae
The ground body colour is black or dark brown with scattered orange-red pustules all over.The pustules have greenish borders (Figs.14A-C).The rhinophores are black, sometimes tipped with orange.The edge of the foot, the rhinophoral sheaths and the oral tentacles may vary from orange to greenish.The gill leaves are green.
anatomy.Nembrotha yonowae shares the same general internal anatomy as other Nembrotha species (Fig. 2).The anterior digestive tract begins with a long but thin oral tube that continues into the buccal mass.Two long, wide salivary glands connect to the buccal bulb at both sides of the oesophageal junction.The thin chitinous labial cuticle is corrugated with a central and two lateral areas devoid of denticles (Fig. 15A).The radular formulae are: 31 mm specimen, 21 x 9.1.1.1.9(WAM S11556), 13 mm specimen (preserved), 20 x 9.1.1.1.9(CASIZ 106531) and 5 mm specimens, 18 x 6.1.1.1.6(CASIZ 082920) (Figs.15B,C).The rachidian teeth are broad and rec-tangular with five asymmetrically arranged triangular denticles almost similar in size (Figs.15B,C).The two inner denticles of the right half of the rachidian teeth are joined at the base.The inner laterals are well developed; they are larger and longer than the outer ones with a rectangular base and two cusps, an elongate terminal cusp and a shorter more basal one.
The outer lateral teeth are rectangular plates, be- coming smaller near the margin.The innermost one bears an upper cusp while the remaining ones lack cusps or dentition (Figs.15B,C).There is a blood gland located above the intestine.
The reproductive system is triaulic (Fig. 16A).The hermaphroditic duct is short and narrow, expanding into an elongate, wide and convoluted ampulla.The postampullary duct divides into a short oviduct and a wide prostatic portion of the vas deferens.The oviduct enters the massive female gland mass.The prostatic segment of the vas deferens is very large.The distal end of the prostatic mass branches into a narrow elongate and highly convoluted vas deferens.The distal end of the vas deferens widens into a muscular ejaculatory portion.The chitinous penial spines are numerous and they seem to be arranged in longitudinal lines.They can be distinguished into three different kinds of spines based on their size and shape (Figs.15E-H).The basal spines are large, elongate and curved.They constitute the first three or four rows of spines (Figs.15E,H).The spines immediately after these are much smaller and hooked (Figs.15F,H).The remaining spines are also hooked and slightly more elongate than the second group but shorter than the basal spines (Figs.15G,H).The vagina is wide, long and slightly convoluted.
remarks.Almost sixty years after Allan's study, Goethel and Debelius (1992) described a new species of Nembrotha from the Maldives, N. yonowae.This species strongly resembles N. nigerrima, N. cristata and N. livingstonei but the authors introduced it based on the presence of orange pustules bordered with green and on its distribution.No anatomical description was given and no available type specimen exists.One year later, Yonow (1993) introduced N. guttata, also from the Maldives.The specimen described by Yonow is identical to N. yonowae but this author stated that as the type specimen of N. yonowae was not available, the illustrations depicted additional material not collected (Fig. 14A), and there are many difficulties in distinguishing the different species within the genus Nembrotha, the specimen described by Goethel and Debelius (1992) could not represent the same species as the one she was describing.We considered that since there are no specimens of N. yonowae to examine, the type locality of both species is the same and the external description is identical, so N. guttata and N. yonowae are synonyms.
Moreover, according to the International Code of Zoological Nomenclature (ICZN 2000), since before 1999 depositing of type material was not required when a new species was described, N. yonowae was described in a publication sensu Article 8.1, and the external description permits the recognition of the species, we consider that N. guttata Yonow (1993) is a junior synonym of N. yonowae Goethel and Debelius (1992).
There are problems of colour variation surrounding the taxonomy of this species.Additional specimens (with a different colour pattern) from the Philippines (Figs. 14D,15D) have also been examined.But since the internal anatomy of the species complex nigerrima-cristata-yonowae is very similar, we are not going to refer those specimens as any of them.Further morphological and molecular studies need to be done to fully resolve these issues.

Nembrotha chamberlaini
remarks.N. chamberlaini Gosliner and Behrens, 1997 is another very similar colour form of N. purpureolineata, N. lineolata and N. megalocera, originally described from the Philippines and Okinawa but also present in Indonesia.The authors provided a complete description of this species based on three specimens but with a single specimen examined and also figured the variation in distribution of colour pattern.In the remarks section for N. chamberlaini a comparison is made with N. lineolata, N. purpureolineata, N. rutilans and N. megalocera and the only consistent difference noted by the authors is the rhinophores and gill leaves having uniform red pigment throughout.The authors also stated that the rachidian teeth of N. chamberlaini and N. purpureolineata are broader near the middle, while in N. lineolata and N. megalocera the rachidian teeth are broadest basally.However, since the number of specimens examined in the present study is higher than in all original descriptions, we can confirm that most of the specimens of N. lineolata and N. megalocera examined also have rachidian teeth broader near the middle and thus it is not an informative character.Regarding the reproductive system, there are no significant differences between N. megalocera, N. lineolata, N. purpureolineata and N. chamberlaini.All these species have a penis without penial spines at the base followed by numerous rows of hooked penial spines.The number of rows is very difficult to determine since it is necessary for the penis to be completely extruded.Our specimens perfectly match those described by Gosliner and Behrens (1997).N. chamberlaini is common at shallow depths, and Gosliner and Behrens (1997) reported it feeding on the tunicates rhopalaea sp., Clavelina moluccensis and oxycorynia fascicularis.Nice pictures of this beautiful species are shown in (http://www.seaslugforum.net/factsheet.cfm?base=nembcham; http://www.medslugs.de/Opi/Nembrotha_chamberlaini.htm).
Figure 14F shows a photograph of one specimen (not collected) from the Philippines, which is very similar to N. chamberlaini and N. purpureolineata but with a different colour pattern.Nembrotha chamberlaini, N. purpureolineata, N. lineolata and N. megalocera are members of the so-called "lined" species of Nembrotha according to the phylogenetic analysis conducted by Pola et al. (2007).Thus, the relationships in this clade based on morphological characters are not resolved.However, molecular data clearly distinguished between these different species.For this reason, we cannot assign the uncollected specimen of Figure 14F to any of the species of the "lined" Nembrotha clade since it was not examined for molecular study.
Geographic range.Thus far this species is known from the Philippines (Gosliner and Behrens, 1997;Debelius, 1996;Debelius and Kuiter, 2007; present study), Okinawa (Okutani, 1994;Gosliner and Behrens, 1997) and Indonesia (Tonozuka, 2003;Debelius and Kuiter, 2007).Other pictures of this species are available from http://www.seaslugforum.net/factsheet.cfm?base=nembcham.Gosliner and Behrens, 1997 (Figs. 14G, 16C, 18) Nembrotha milleri Gosliner and Behrens, 1997: 296,  external morphology.Gosliner and Behrens (1997) provided a complete description of the external anatomy of this species.The specimens examined for the present study matched their descriptions and there is no additional information presented.See Figure 14G for a photo of a living animal from the Philippines.

Nembrotha milleri
anatomy.Nembrotha milleri shares the same general digestive anatomy as other Nembrotha species (Fig. 2).The anterior digestive tract begins with a large and long oral tube that continues into the buccal mass.Both are almost similar in size.There is a pair of large and wide salivary glands on the buccal mass, flanking the oesophagus.The labial cuticle forms a brown corrugated chitinous disk, but without any armature or rodlets.The radular formulae are: 55 mm specimen, 30 x 10.1.1.1.10(CASIZ 096302), 78 mm specimen, 26 x 10.1.1.1.10(MNCN 15.05/46720), 85 mm specimen, 30 x 10.1.1.1.10(MNCN 15.05/46721), 112 mm specimen, 30 x 10.1.1.1.10(AM C205319), 30 mm specimen (preserved), 27 x 11.1.1.1.11(AM C205320), and 120 mm specimen, 35 x 14.1.1.1.11(WAM S11559) (Figs. 18A-D).The rachidian teeth are broad, variable in shape, usually with five asymmetrically arranged triangular denticles.The two outermost denticles are a bit smaller than the inner ones.Usually, two of the inner denticles are joined at the base but the arrangement of these denticles may vary from the right to the left side (Figs.18A-D).In one of the dissected specimens (MNCN 15.05/46720), there are only four symmetrical denticles (Fig. 18B).The inner laterals are larger than the outer ones with a rectangular base and two cusps, an elongate terminal cusp and a shorter more basal one.The three inner outer laterals bear large cusps of decreasing size, while the remaining laterals are rectangular without cusps (Fig. 18A).There is a large blood gland located in between the intestinal loop.A cup-shaped renal syrinx is present under the pericardium, close to the anal papilla.An elongate and muscularised ventriculum is present but not visible under the thick pericardium.
The reproductive system is triaulic (Fig. 16C).The hermaphroditic duct is relatively long and narrow.It expands into an elongate and slightly convoluted ampulla.The prostatic portion of the vas deferens is very large.The distal end of the prostatic mass connects to an elongate and highly convoluted vas deferens.The distal end of the vas deferens widens into a muscular ejaculatory portion.The penis is armed with numerous penial spines.They can be distinguished into three different kinds of spines arranged in longitudinal lines (Figs. 18E,F).The short uterine duct emerges from the female gland and joins the pyriform seminal receptacle via a short and curved duct and continues proximally until it widens, joining with the vagina.Together they enter the rounded, thin-walled bursa copulatrix, which, in situ, is entirely surrounded by the prostate.The elongate, wide and straight vagina also emerges from the base of the bursa and shares a common base with the uterine duct.
remarks.The specimens we examined of N. milleri closely match the description of Gosliner and Behrens (1997).However, the rachidian teeth and the penial spines of the animals we examined differed slightly from Gosliner and Behrens's description.Gosliner and Behrens (1997) described four denticles on the rachidian teeth but this is probably an aberration rather than a diagnostic feature, since within the specimens examined in this study only one specimen had four denticles instead of the typical five (Fig. 18B).In their study, the penial spines also differ from those of our specimens.It appears that in the single specimen dissected by the authors the pe- nis was not completely extended, so they described only two types of penial spines.However, the penis of our specimens is armed with three different types of spine: the basal ones elongated and curved; the ones immediately distal to them short and curved; and the distal ones medium-sized and about twice the length of the shortest ones.Nembrotha milleri is clearly distinguishable from the other species of the genus by its robust, wrinkled green body.N. kubaryana and N. cristata also have green pigmentation on the body but it is found on large rounded tubercles, which are absent in N. milleri.
Geographic range.Originally described from the Philippines and Indonesia (Gosliner and Behrens, 1997), this species is also known from Norfolk Island (Coleman, 2001), Western Australia (Coleman, 2001; present study), Kerama and the Ryukyu Islands (Ono, 1999;2004;present study) and Tanzania (Debelius and Kuiter, 2007).Gosliner and Behrens, 1997 (Figs. 14H, 16D, 19) Nembrotha mullineri Gosliner and Behrens, 1997: 300,  external morphology.Gosliner and Behrens (1997) provided a complete description of the external anatomy of this species.The specimens examined for the present study matched their descriptions and thus there is no additional information to present.See Fig. 14H for photo of living animal from the Philippines.

Nembrotha mullineri
anatomy.Nembrotha mullineri shares the same general digestive anatomy as other Nembrotha species (Fig. 2).The anterior digestive tract begins with a large and muscular oral tube that continues into the buccal mass.The buccal mass is larger than the oral tube.There is a pair of large and wide salivary glands on the buccal mass, flanking the oesophagus.The labial cuticle forms a brown corrugated chitinous disk, but without any armature or rodlets.The radular formulae are: 38 and 60 mm specimen (preserved), 27-29 x 11-10.1.1.1.10-11 (CASIZ 103724;CASIZ 106508), 85 mm specimen (preserved), 32 x 11.1.1.1.11 (CASIZ 158269), 98 mm specimen, 25 x 11-10.1.1.1.10-11 (MNCN 15.05/46723) and 113 mm specimen, 29 x 11-10.1.1.1.10-11(AM C205321) (Fig. 19A).The rachidian teeth are broad and variable in shape, with five asymmetrically arranged triangular denticles.The two outermost denticles might be a bit smaller than the inner ones.Usually, the two inner denticles of the right side are joined at the base (Figs.19A-D).The inner lateral teeth are elongate and larger than the outer ones with a rectangular base and two cusps, an elongate terminal cusp and a shorter more basal one.The three inner outer laterals bear large cusps of decreasing size, while the remaining laterals are rectangular without cusps (Fig. 19A).There is a large blood gland located in between the intestinal loop.A cup-shaped renal syrinx is present under the pericardium, close to the anal papilla.An elongate and muscularised ventriculum is present but not visible under the thick pericardium.
The reproductive system is triaulic (Fig. 16D).The hermaphroditic duct is relatively long and narrow.It expands into an elongate and highly convoluted ampulla.The prostatic portion of the vas deferens is very large.The distal end of the prostatic mass connects to an elongate and highly convoluted vas deferens.The distal end of the vas deferens widens into a muscular ejaculatory portion.The penis is armed with numerous penial spines, which can be distinguished into three different kinds of spines arranged in longitudinal lines (Figs. 19E,F).The uterine duct emerges from the female gland and joins the pyriform seminal receptacle via a short, curved duct and continues proximally until it widens, joining with the vagina.Together they enter the rounded, thin-walled bursa copulatrix, which, in situ, is entirely surrounded by the prostate.The elongate, wide and straight vagina also emerges from the base of the bursa and shares a common base with the uterine duct.
remarks.Nembrotha mullineri is distinctive as it is the only member of the genus with a creamcoloured body with brown spots and blotches.The extent of brown colouration is quite variable from specimen to specimen: from a simple series of spots and lines to dense patches of brown.The specimens of N. mullineri we examined closely match the description of Gosliner and Behrens (1997).However, Gosliner and Behrens (1997) described N. mullineri as "unique among described members of the genus in having an arched masticatory margin without distinctly separated denticles", while our specimens have the rachidian teeth very similar to the remaining species of the genus, with five asymmetrically denticles on the masticatory margin.Since Gosliner and Behrens only dissected one specimen from their type material, and we have dissected more specimens including two paratypes, we conclude that the rachidian teeth described by these authors were just an aberration of that specimen.Regarding the penial spines, they are very similar to that of N. cristata, N. guttata and N. milleri but the number and distribution of the penial spines is difficult to determine with precision because they are dependent on the degree of extension of the penis when they were preserved.
Geographic range.Originally described from the Philippines (Gosliner and Behrens, 1997), this species is also known from Indonesia (Tonozuka, 2003), Vietnam (Debelius and Kuiter, 2007), Eastern Australia (Ellis, 1999)  etymology.The specific name refers to the large pink rings.external morphology.The body is elongate and limaciform but robust and widest at the level of the gill circle (Figs.20A-D).The posterior end of the foot is long and pointed.The head is rounded.The preserved animals are 55-60 mm long.The living animals are large, reaching up to 120 mm.The body wall is highly muscularised.The entire body surface is textured with a pattern of longitudinal wrinkles and with large disconnected blunt tubercles arranged on the notum and on both sides of the body.The tubercles extending around the head suggest a wide mantle margin.The margin may continue as a broken series of tubercles along the edge of the mantle until the end of the foot.Dorsally, from the anterior margin to the base of the gill branches, there are usually three large tubercles.On both sides of the body there are a variable number of similar scattered tubercles.The number and the arrangement of these protruding structures vary in different individuals (Figs.20A-D).There is a pair of large and conical, perfoliate rhinophores, bearing around 35 lamellae.The rhinophores are completely retractile into their elongate rhinophoral sheaths.The oral tentacles are circular in shape with a depression at the centre of each.The two posterior gill branches on each side have a common base.The genital aperture is located on the right side, midway between the gill and the rhinophores.
The ground colour is olive green (Figs.20A-D).The tubercles are black bordered with wide circular rings of pink colour.The anterior edge of the notum is pink with some black spots.The outer rachis of each gill branch (except the base), the subapical area of the rhinophoral sheaths and the base of the oral tentacles are also pink.The rhinophores and the pinnae are black, the same colour as the centre of the tubercles, the tip of the rhinophoral sheaths and the tip of the oral tentacles.The foot is blue or purple.The rings on the larger adults are generally fluorescent bright pink, while the rings on the juveniles tend to be bright orange in colour (Harasti, pers.comm., Fig. 20D).
anatomy.Nembrotha rosannulata shares the same general digestive anatomy as other Nembrotha species (Fig. 2).The anterior digestive tract begins with a long muscular oral tube that continues into the buccal mass.The buccal mass is nearly the same size as the oral tube.A pair of elongate, wide granular salivary glands connects to the buccal bulb at both sides of the oesophageal junction.The chitinous labial cuticle is corrugated but without any armature or rodlets.The radular formula of the 55 mm specimen (preserved) is 30 x 9.1.1.1.9(Fig. 21A).The rachidian teeth are broad and quadrangular with five triangular denticles of the same size (Fig. 21B).The inner laterals are larger and longer than the outer ones with a rectangular base and two cusps, an elongate terminal cusp and a slightly shorter more basal one.The second and third laterals bear large cusps of decreasing size, while the remaining laterals are rectangular without cusps (Fig. 21A).There is a very large blood gland located above the dorsal surface on the oesophagus.A cup-shaped renal syrinx is present under the pericardium, close to the anal papilla.An elongate and muscularised ventriculum is present but not visible under the pericardium.
The reproductive system is triaulic (Fig. 16E).The hermaphroditic duct is short and wide.The ampulla is large and convoluted.It branches into a short oviduct and the prostate.The oviduct enters the massive female glands, which in the specimen dissected is very well developed.The prostatic segment of the vas deferens consists of a large, wide portion, which has a dense network of interconnecting tubules over its surface.It connects to an elongate straight section followed by a long, narrow and highly convoluted ejaculatory segment, which opens into a common atrium with the vagina and the female gland.The penis is located in the latter portion.The chitinous penial spines are numerous and arranged in longitudinal lines (Figs. 16C-F).It appears that there are at least two kinds of penial spines.The spines at the base of the penis are smaller and more hooked than the distal ones (Fig. 16C-F), increasing their size gradually along the penis.The vagina is long, wide and straight.At its proximal end, the vagina connects to the large and rounded bursa copulatrix.From the bursa copulatrix leads another duct connecting to the seminal receptacle and the uterine duct.This duct is initially of the same diameter as the vagina but it narrows about half way to the uterine duct.The seminal receptacle is pyriform and smaller in size than the bursa copulatrix.There is no accessory gland.In situ, the bursa is totally surrounded by the prostate.
remarks.In a recent publication (Delbelius and Kuiter, 2007, p. 59) a species is identified by the name Nembrotha rosannulata Pola, 2006.That name was inadvertently used because the authors did not follow the advice of reviewers that this was a species manuscript name that was still unpublished.Thus, Debelius and Kuiter introduced a nomen nudum and the name is not available in accordance with the International Code of Zoological Nomenclature (ICZN art.16.1 and 16.4).The formal name should be Nembrotha rosannulata Pola, Cervera and Gosliner, 2008.Prior to the publication of Debelius and Kuiter's book (2007), this species has been commonly referred to as "Donut Nembrotha" because of the large pink rings that look like donuts on their body.This feature makes it distinctly different from any other species of the genus and it is actually considered "naturally rare" in New South Wales (Harasti, pers. comm.).Nembrotha rosannulata and N. milleri are both robust species, which have green ground colour.However, N. milleri lacks the large pink rings and its penis has three different types of penial spines, while in N. rosannulata there appear to be only two kinds.Nembrotha kubaryana and N. livingstonei also have only two different kinds of penial spines but they are easily distinguishable from N. rosannulata by the external colouration.
Geographic range.Thus far this species is known only from New South Wales, Australia (present study, Coleman, 2001)  etymology.The specific name refers to the beautiful golden colour ornamenting the dorsal surface of the animal.From latin: "aureus" = golden (having the colour of gold; highly ornamented).external morphology.The body is elongate and limaciform, reaching up to 55 mm in length in living adults (Figs.20E-F).The posterior end of the foot is long and pointed.The head is rounded.The body surface is corrugated.The dorsum continues to the side of the body without a line of demarcation or pallial edge.Externally the animals are characterised by the presence of longitudinal stripes and large patches of bright colouration.Usually, the stripes are arranged as follows: one strong stripe on the middorsal line between the rhinophores and the gill and two shorter ones of the same width on each side of the middle stripe; a thinner stripe round at the margin of the mantle, and back on each side of the notum.
Behind the gill, these two lines converge and meet to form a single line, about halfway between the gill and the posterior end, which runs back to the end of the foot.Thus, there are three to seven longitudinal lines on each side of the body (Figs.20E-F).There is a pair of large conical, perfoliate rhinophores that bear around 30 lamellae and are completely retractile into their elongate rhinophoral sheaths.The oral tentacles are thick and elongate with a depression at the centre of each one.There are three large multipinnate, non-retractile branchial leaves.The anus is mid-dorsal, located in the centre of the branchial circle on an elevated, elongate papilla.The genital pore opens on the right side, midway between the rhinophores and the anterior portion of the gill.
The ground colour of the body is white.The stripes are brown in colour.A large orange yellow patch is present in the middle on the back and in the midlength of the posterior end of the foot (Figs.20E-F).The oral tentacles and the margin of the foot are delineated by a blue to purple band.The rhinophores are red.The rhinophoral sheaths are white bordered with light blue to purple according to specimens.The branchial leaves are red.The rachis of each gill and the base of the gill are also light blue or purple.It is also possible to find specimens without a trace of blue or purple colour on the rhinophoral sheaths or the gill.The sole is colourless.
anatomy.Nembrotha aurea shares the same general internal anatomy as other Nembrotha species (Fig. 2).The anterior digestive tract begins with a long, thin muscular oral tube that continues into the buccal mass.The buccal mass is smaller than the oral tube.There is a pair of large, wide salivary glands on the buccal mass, flanking the oesophagus.The labial cuticle forms a brown corrugated chitinous disk, devoid of rodlets but with a central and two lateral areas.The radular formulae of the paratypes are: 20 mm specimens, 21 x 6.1.1.1.6and 23 x 7-6.1.1.1.6-7(MNHN-Paris), 25 mm specimen, 21 x 6.1.1.1.6((MNHN-Paris).The rachidian teeth are variable in shape (Figs.22A-C).Usually, they are broad and hexagonal with the upper side narrower than the basal one.The masticatory margin has five triangular denticles, the two outer ones much smaller than the inner ones.The two inner denticles of the right side are distally joined.In one specimen, the two joined denticles were those of the left side and they were joined at the base.The inner laterals are well developed; they are large and strongly hooked with two cusps.The outer lateral teeth are rectangular plates, from 6 to 7, which lack cusps or dentition and become smaller near the margin (Fig. 22A-C).
The reproductive system is triaulic (Fig. 16F).The hermaphroditic duct is elongate and wide.It expands into a very long and highly convoluted ampulla.The long straight postampullary duct branches into the prostatic portion of the vas deferens and the short oviduct that connects to the female glands.The prostatic portion of the vas deferens is very large and consists of a spherical mass, which appears as a dense network of interconnecting tubules entirely surrounding the bursa copulatrix.The distal end of the prostatic mass connects to an elongate, highly convoluted vas deferens.The vas deferens opens into a common atrium with the vagina but without a strongly differentiated muscular ejaculatory portion.The penis is armed with rows of curved, chitinous hooks except at the base.The chitinous penial spines are numerous and they are similar in size and shape (Fig. 22D).The vagina is very wide, long and convoluted.At its proximal end, the vagina connects to the rounded, thin-walled bursa copulatrix.In situ, the bursa copulatrix is entirely surrounded by the pros-tate.In Figure 16F, the prostate is shown positioned to the side.From the bursa copulatrix leads another convoluted duct that connects to the pyriform seminal receptacle and the female glands via the uterine duct.The vagina is separated from the vas deferens along its entire length.There is no vaginal gland.
remarks.Nembrotha aurea is described from South Africa, Tanzania, Mozambique and the Comoros Islands.This species is easily distinguishable from N. lineolata and N. purpureolineata by the large orange yellow patch over the middle of the back and the tail.The pattern of lines is also different from the latter species.The longitudinal stripes in N. lineolata are rather narrow and more numerous than in N. aurea while in N. purpureolineata there is only one broad stripe on the notum.The rachidian teeth of N. purpureolineata are broader than those of N. aurea, while the shape of the rachidian teeth of N. lineolata appears to vary from both extremes.There are no significant differences in the reproductive anatomy of these three species.The external and internal anatomy of our specimens is very similar to those of the specimens described by Baba (1976) from Japan as Nembrotha purpureolineata O'Donoghue, 1924 (for a picture of a similar living animal see Nakano, 2004).The major difference between Baba's specimens and our examined material is the presence of only one strong stripe on the mid-dorsal line.Nevertheless, photographs of additional specimens from Japan (Suzuki, 2000), Indonesia (Debelius, 1996;Tonozuka, 2003) and Western Australia (Coleman, 2001) (Figs. 20G-H) show the same three strong stripes on the notum as N. aurea, but those specimens have fewer longitudinal lines on both sides of the body.Since we have not been able to examine any of those specimens and the geographical range is far away from the type of N. aurea, we cannot confirm that both Baba's (1976) specimens and the specimens in the above field guides are variant colour forms of N. aurea.

DISCUSSION
The genus Nembrotha is distributed throughout the tropical Indo-Pacific, from South Africa to Eastern Australia, but it is absent from other tropical areas in the Atlantic and the Eastern Pacific.Recently, Pola et al. (2005Pola et al. ( , 2006a,b) ,b) proposed several phylogenies of the genera roboastra and tambja based on both morphological and molecular data.These studies demonstrate that the genus roboastra is monophyletic, based on morphological characters, while the genus tambja appears to be paraphyletic no matter which traditional classification is chosen.In these studies only a few species of Nembrotha were included in the analysis, so a hypothesis about the relationships of Nembrotha and its origin was not proposed.Nevertheless, Pola et al. (2007) analysed the Phylogenetic relationships of Nembrothinae based on both morphological and molecular markers.In this case, the monophyly of the genus Nembrotha was recognised in all the analyses.Moreover, within Nembrotha two well-supported major clades were recovered.
There are several synapomorphies of Nembrotha, including the fact that they feed on tunicates, that the labial cuticle forms a brown corrugated weak chiti-nous disk usually devoid of rodlets but with a central and two lateral areas, and that they have a very well differentiated prostate that completely surrounds the bursa copulatrix.Within Nembrotha, there appear to be two different groups of species that are easily distinguishable based on their external pattern.One group includes N. nigerrima, N. cristata, N. yonowae, N. livingstonei, N. milleri, N. mullineri and N. rosannulata, characterised by having large pustules or spots scattered on the body; and the other group includes N. lineolata, N. purpureolineata, N. chamberlaini, N. megalocera and N. aurea, characterised by having longitudinal lines or bands on the notum.Regarding the internal anatomy, the radular teeth and the reproductive system are very similar in all Nembrotha species.However, the "lined" group have a penis with only one type of penial spines, none of them at the base, while within the "spotted" group N. cristata, N. yonowae, N. milleri and N. mullineri appear to have two or three different types of penial spines.Nembrotha nigerrima, N. livingstonei and N. rosannulata only have two different types of penial spines, in all cases starting at the base of the penis.Other differences in the reproductive system between both groups of species are a convoluted ampulla and a straight vagina present in N. nigerrima, N. cristata, N. yonowae, N. livingstonei, N. milleri, N. mullineri and N. rosannulata, whereas N. lineolata, N. purpureolineata, N. chamberlaini, N. megalocera and N. aurea have a highly convoluted ampulla and a convoluted vagina.
Steps towards the synonymisation of some species of Nembrotha have been suggested by different authors (Eliot, 1904(Eliot, , 1906;;Baba, 1976;Yonow, 1990;Yonow and Hayward, 1991).Rudman (1998Rudman ( -2005) ) shows that the colour pattern of Nembrotha species is extremely variable and also suggests that most of the species may be varieties of the same species, but insufficient anatomical evidence has been provided to demonstrate this proposal.The other interesting aspect is that some members of these complexes are sympatric, thus reducing the possibility that they are just geographical variants of a single species.Since the external variability within Nembrotha is very high and we have not been able to examine all different colour forms and intermediate states of each species, in this paper we have preferred to adopt a conservative point of view and thus to maintain most of the nominal species of the genus.Further anatomical and molecular studies, as well as studies of populations, need to be done in order to determine
and Western Australia (present study).