Two unknown species of Mollusca Gastropoda from the Archipelago Fernando de Noronha ( Brazil ) , with description of a new species belonging to the genus Phidiana Gray , 1850 and a new record of Dendrodoris senegalensis Bouchet , 1975 *

The Brazilian Archipelago of Fernando de Noronha lies off Cape Sao Roque, State of Rio Grande do Norte, about 195 nautical miles offshore. Only a few faunistic lists of this tropical archipelago have been published, and only four species of Gastropoda Opisthobranchia were cited. In this paper two species of Opisthobranchia Nudibranchia are recorded from this Archipelago. Dendrodoris senegalensis Bouchet 1975, known from Cape Verde and Senegal, amplifies its extension range toward the Western Atlantic. The brazilian specimens differ from the African specimens, in the presence of a completely white branchial tuft. Phidiana riosi sp nov clearly differs from other co-generic species in its colour pattern, having a red ground colour, with numerous white spots scattered on the dorsum. The rhinophores are orange and the cerata white with the cnidosac orange. Internally, this species has jaws with a single row of denticles, and the radular teeth have a central cusp with 7-8 denticles each side. The penis is armed with a black spine and the seminal receptacle connects with two independent ducts, the oviduct and the vaginal duct. Both species are compared with other similar taxa.


INTRODUCTION
The Brazilian Archipelago of Fernando de Noronha lies off Cape Sao Roque, State of Rio Grande do Norte, about 195 nautical miles offshore (Fig. 1). It is composed of several islands of volcanic origin, lying in the north branch of the South Equatorial Current. This Archipelago was used as a Brazilian prison, but is preserved as a National Park. The islands are composed mostly of hard substrate with only a few sandy beaches, dominated by Sargassum and calcareous algae bottoms. The marine fauna of the archipelago is poorly known. Only a few taxonomic lists have been published (Laborel, 1969;Matthews and Kempf, 1970;Fausto Filho, 1974;Eston et al., 1986). In 1970, Matthews and Kempf revised the mollusc fauna from Atol das Rocas and Fernando de Noronha, and listed 77 and 168 species of molluscs respectively. However, only four species of gastropod opisthobranchs were cited: Micromelo undata (Bruguière, 1792), Hydatina vesicaria (Solander, 1786), Retusa canaliculata (Say, 1827) and Cylichna noronhensis Watson, 1883.
Two previously unrecorded species of nudibranchs were collected during the accomplishment of the project "Moluscos do Parque Nacional Marinho de Fernando de Noronha" (reference IBAMA licença 070/99), organised by Prof. Ricardo S. Absalão, from the Department of Zoology of the Federal University of Rio de Janeiro (Brazil). One of them was identified as Dendrodoris senegalensis Bouchet, 1975  External anatomy (Figs. 2A,B;3,4A): The body is elongated; length between 11 and 18 mm. The oral tentacles are long (3.2-5 mm) and cylindrical. The rhinophores are slightly shorter than the oral tentacles, having 6-7 large annulations and 6-7 shorter annulations intercalated between them. The eyes lie behind the base of the rhinophores.
The cerata are cylindrical and the cnidosac is pointed. The precardiac cerata are arranged in five oblique rows and the postcardiac ceratal clusters are arranged in seven oblique rows, having one ceratal row per branch of the posterior liver duct. The outer cerata of the rows are shorter than the inner ones. The number of cerata per cluster in the 17 mm specimen is: precardiac rows with 3, 5, 7, 8 and 7 cerata respectively on the right side and 5, 4, 7, 7 and 7 cerata respectively on the left side. The postcardiac rows with 3, 6, 5, 3, 3, 2 and 2 cerata respectively on the right side and 7, 5, 6, 3, 4, 2 and 2 cerata respectively on the left side. The genital papilla is situated on the right side of the body, below the fourth precardiac ceratal row. The anus opens between the last precardiac ceratal row and the first postcardiac row. The foot is narrow and the propodial tentacles are absent. ON  When the animals are disturbed, the rhinophores are directed forward, the body is slightly curved and the cerata are straight, showing a symmetrical disposition along the animal. The innermost cera of some ceratal rows become erect, while the others stand out horizontally (Fig. 2B).
The ground colour is reddish with numerous white spots on the dorsal and lateral surfaces of the body. The basal third of the oral tentacles is reddish with white spots, the middle third is orange and the apical third is hyaline white. The foot is reddish. The rhinophores are orange with a white tip. The cerata have the surface of cnidosac area orange; the subapical area of the cerata are white with a translucent basal third. Dark brown digestive gland branches are visible through the translucent tissue.
Internal anatomy: The jaws are colourless, ovate and convex on the outer surface. The masticatory border has a single row with 17 rounded denticles in a specimen of 17 mm in length (Figs. 4B, 5A). The radular formula of the same specimen is 13 x 0.1.0. The teeth have a median cusp and 7-8 hooked denticles on either side. Outer denticles are bigger than median denticles (Figs. 4C, 5B,C).
Reproductive system (Fig. 6). The hermaphroditic duct widens into a convoluted ampulla, which divides into an oviduct and a short deferent duct. The oviduct connects separately with an ovoid seminal receptacle. The distal end of the vaginal duct connects with the seminal receptacle next to the oviduct. The deferent duct lacks a morphological differentiated prostate. The penis is cylindrical and armed with a pointed apical black spine. 1/4 the body 1/3 the body 1/3-1/6 the body 1/6 the body longer than similar than length length length length rhinophores rhinophores Rhinophores 6-7 complete lamellae with low smooth, sometimes smooth, distinctly 3-5 large complete flanges smooth and 6-7 intercalated pustules with wrinkled inflated in the small lamellae bases central region Anus below the 1st between 2nd and between the lower base of the anterior base of 3 row of between two central postcardiac ceratal 3rd ceras in cerata of 4 row in the rows of the 2nd the 2nd ceratal rows of 2nd row ninth row 1st post-pericardial cluster cluster cluster cluster Cerata arranged in 12 single arranged in 6 single, arranged in 6-9 cluster 6 precardial oblique 3-4 clusters widely 9 cluster of 2 oblique oblique rows parallel, oblique with oblique rows; 5 postcardial clusters spaced of rows, 1st cluster rows rows. 1st cluster with 6,4,3,4,4 oblique rows with 5 rows with 6-9 rows oblique rows Remarks: This species belongs to the genus Phidiana because it has long oral tentacles, the rhinophores are lamellate, the foot is anteriorly rounded, all the ceratal clusters are disposed in oblique rows, the jaws have a masticatory border with a row of denticles, the radular teeth are provided with lateral denticles on a central cusp and the penis is armed with a spine. A comparative table of Phidiana species is presented in Table 1. Only one species of Phidiana has been described from Brazilian coasts, P. lynceus Bergh, 1867, which differs clearly from our specimens in the colour pattern; P. lynceus has a white line running mid-dorsally which branches up the basal parts of the oral tentacles, and orange bands on the rhinophores and oral tentacles. Furthermore, there are several ceratal rows from each branch of the posterior liver duct, while there is only one row per branch in P. riosi. Finally, in the reproductive sys- cusp and 8-10 cusp and 8-10 cusp. 4-5 lateral cusp, 4-5 lateral 6 lateral lower margin of lateral denticles lateral denticles denticles denticles denticles the teeth, central cusp with 3-4 smaller denticles Masticatory 25-30 irregular with 18 denticles 2 rows of a row with 15 -22 -a row of large a row of border of jaws blunt denticles denticles hooked denticles denticles denticles and oviduct to  single  single  -single  --seminal receptacle Penial stylet present present present present -absent present tem of P. riosi the seminal receptacle is serial with two independent ducts (oviduct and vaginal duct), while there is only one duct in P. lynceus.

Connection of vagina
Other species of Phidiana with reddish or orange colour are P. lottini (Lesson, 1831), P. lascrucensis Bertsch andFerreira 1974 andP. mariadelmarae García andTroncoso 1999, all of them from Pacific Ocean. P. lottini is grey whitish, some times reddish, having two white spots lying anterior and posteriorly to the rhinophores; the cerata are organized in 20-26 rows and the radular teeth only have 6 lateral denticles (Engel, 1925;Marcus, 1959, cited as P. inca). P. lascrucensis is orangish to orange-yellow with numerous white specks scattered randomly along the dorsum, and the jaws are characterised by the presence of a masticatory border with two rows of denticles (Bertsch and Ferreira, 1974). P. mariadelmarae is orange having a middorsal longitudinal white line that bifurcates at the base of the rhinophores, and only one duct joining the seminal receptacle in the reproductive system (García and Troncoso, 1999).
In warm western Atlantic waters, fourteen facelinid species have been described. Among them, only Facelina coenda Marcus, 1958 has the cerata in rows (Marcus, 1958). However this species differs from P. riosi in the coloration and in the spines of the penis (Marcus, 1958). Bouchet 1975 (Figs. 2 C, D, E, F, 7, 8) Material examined: Two specimens 9 and 14 mm in length, collected at 14 m depth at Rata Island (19/06/2000). One specimen, 21 mm in length, collected at the intertidal zone at Fernando de Noronha Island (07/07/1999).

Dendrodoris senegalensis
External anatomy (Figs. 2 C-F): The body is soft and smooth, lacking spicules. The notal margin is delicate and slightly striated. The rhinophores have a cylindrical stalk and the club is lamellate. The branchial tuft has five moderately long tripinnate gills arranged in a circle. The anal papilla lies at the centre of the branchial circle. The oral tentacles are absent.
Coloration (Figs. 2 C, D, E, F): The dorsal surface and notal margin are uniformly red except in the 21 mm long specimen, which is red-brown with irregular white areas (Fig. 2E). The rhinophores are red with the tip white. The gills are uniformly white. The anal papilla is uniformly white too. Ventrally, the notal margin and foot are white with small red spots (Fig. 2F).
Internal anatomy: An impair ptyaline gland is connected to the buccal bulb. The oesophagus is long, with two small oesophageal glands near to the buccal bulb. The intestine has a small pyloric gland. The heart is connected through the aorta to the blood gland (Fig. 7).
The reproductive system has an ovotestis lying interdigitating on the anterior portion of the digestive gland (Figs. 7, 8). The hermaphroditic duct connects with a short and enlarged ampulla. The deferent duct has a proximal prostatic portion and a narrow and folded distal region. The male eversible cirrus has numerous hooks with slightly elongate bases. The gametolytic gland is spherical. A separate duct connects with the smaller, long stalked seminal receptacle just before it enters the female gland mass.

Remarks:
On Brazilian coasts only one species of Dendrodoris has been described, D. krebsii (Mörch, 1863) (Marcus, 1977;Rios, 1994 al., 1996), which differs from our specimens in the coloration; besides this, the notal margin is clearly wider in D. krebsii, the blood gland is larger and the reproductive system of D. krebsii has the ampulla with a fold, and the length of it and the prostate are greater than those of our specimens. Finally, the male cirrus of our specimens has hooks with very short bases, whereas they are large in D. krebsii (Valdés et al., 1996). D. senegalensis is known from Cape Verde and Senegal, on the east coast of Africa (Bouchet, 1975;Valdés et al, 1996). The real geographic range of this species is unknown, owning to the lack of sam-pling effort in this part of the World. Our specimens differ from those from Africa in the coloration of the gills. Bouchet (1975) and Valdés et al (1996) stated that the gills of D. senegalensis have the same coloration as the dorsum, having the external border white; however in the Brazilian specimens the gills and anal papilla are uniformly white, clearly different from the dorsum, which is red or red brown with white irregular spots. Internally, our specimens coincide with the descriptions of D. senegalensis by Bouchet (1975) and Valdés et al. (1996).
As stated above, the Fernando de Noronha Archipelago lies in the north branch of the South Equatorial Current. It is possible that larvae are able to cross the Atlantic Ocean in this area, which is the narrowest point, following the ocean currents. As the only consistent difference of our specimens is the presence of a white gill, and coloration is extremely variable in species of Dendrodoris, we consider that our specimen belongs to the species D. senegalensis, providing a considerable range extension for this taxon.