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Stiphodon mele n. sp., a new species of freshwater goby from Vanuatu and New Caledonia (Teleostei, Gobiidae, Sicydiinae), and comments about amphidromy and regional dispersion Philippe KEITH Muséum national

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Stiphodon mele n. sp., a new species of freshwater goby from Vanuatu and New Caledonia (Teleostei, Gobiidae, Sicydiinae), and comments about amphidromy and regional dispersion Philippe KEITH Muséum national d Histoire naturelle, Département Milieux et Peuplements aquatiques, Ichtyologie, case postale 26, 57 rue Cuvier, F Paris cedex 05 (France) Gérard MARQUET 96 rue de Richelieu, F Paris (France) Marc POUILLY Antenne IRD, UR 131, Universidad Mayor de San Simón, Unidad de Limnología y Recursos Acuáticos, Casilla postale 2352, Cochabamba (Bolivia) Keith P., Marquet G. & Pouilly M Stiphodon mele n. sp., a new species of freshwater goby from Vanuatu and New Caledonia (Teleostei, Gobiidae, Sicydiinae), and comments about amphidromy and regional dispersion. Zoosystema 31 (3) : KEY WORDS Teleostei, Gobiidae, Stiphodon mele n. sp., Vanuatu, New Caledonia, freshwater, amphidromy, new species. ABSTRACT Stiphodon mele n. sp. is described on the basis of material collected from Vanuatu and New Caledonia. It is distinguished from all other congeners in having 9 segmented rays in the second dorsal fin, usually 13 pectoral rays, fine tricuspid premaxillary teeth, 2 small symphyseal teeth in female vs. 2-4 stout teeth in males, predorsal scales absent, and low number of scales in transverse back (3-7) and lateral series (14-21). This new species spawns in freshwater, the free embryos drift downstream to the sea where they undergo a planktonic phase, before returning to the rivers to grow and reproduce: it is an amphidromous species. As many other Sicydiinae, Stiphodon mele n. sp., is endemic to Vanuatu and New Caledonia. Numerous factors occur to control the dispersion of the amphidromous species. It is necessary to consider all of these factors to explain the existence of many endemic species and the broad or small distribution of the species in the Indo-Pacific area. The management and the conservation of Stiphodon mele n. sp. have to be necessarily regional. Publications Scientifiques du Muséum national d Histoire naturelle, Paris. 471 Keith P. et al. MOTS CLÉS Teleostei, Gobiidae, Stiphodon mele n. sp., Vanuatu, Nouvelle-Calédonie, eau douce, amphidromie, nouvelle espèce. RÉSUMÉ Stiphodon mele n. sp. une espèce nouvelle de gobie d eau douce du Vanuatu et de Nouvelle-Calédonie (Teleostei, Gobiidae, Sicydiinae) et commentaires sur l amphidromie et la dispersion régionale. Stiphodon mele n. sp. est décrit à partir de matériel récolté au Vanuatu et en Nouvelle-Calédonie. Il se distingue des autres espèces du genre par la présence de 9 rayons segmentés dans la seconde nageoire dorsale, 13 rayons aux nageoires pectorales, 36 à 41 dents prémaxillaires tricuspides, 2 petites dents symphyséales chez les femelles et 2 à 4 chez les mâles, aucune écaille dans la région prédorsale et moins d écailles en série transverse postérieure (3-7) et en série latérale (14-21). Cette espèce nouvelle pond en eau douce, les embryons libres sont entraînés vers la mer où ils vont mener une vie planctonique avant de revenir vers les rivières pour les coloniser, grossir et s y reproduire : c est une espèce amphidrome. Comme beaucoup d autres Sicydiinae, Stiphodon mele n. sp., est endémique du Vanuatu et de la Nouvelle-Calédonie. De nombreux facteurs contrôlent la dispersion des espèces amphidromes. Il est nécessaire de considérer tout ces facteurs dans la région Indo-Pacifique pour expliquer l existence des endémiques et leur répartition large ou réduite. La gestion et la conservation de Stiphodon mele n. sp. doivent être nécessairement régionales. INTRODUCTION The freshwater ichthyofauna of Vanuatu is both rich and varied but remained poorly sampled until 1998 and, as a result, little has been published on these animals over the centuries (see Keith et al. 2004a). In 1998, the Environment Unit of Vanuatu sponsored a survey of freshwater environments throughout the islands of Vanuatu (Gerbeaux et al. 1998; Keith et al. 2002, 2004a, b, 2007a, b). Between 2002 and 2008, the Muséum national d Histoire naturelle, Paris (MNHN) conducted numerous surveys of fishes occurring in freshwater streams and rivers on the islands of Maewo, Santo, Tanna, Ambae, Efate, Malekula and Gaua, and in 2006, an extensive effort was made in Santo rivers with the SANTO 2006 Expedition (for a narrative of the expedition, see Bouchet et al. 2008, and for a review of the geography and natural history of Santo, we refer to Bouchet et al. in press). The freshwater ichthyofauna of New Caledonia is also both rich and varied but remained poorly known until the end of the 20th century. Between 1998 and 2003, the MNHN conducted, with the provincial and territorial authorities, an exhaustive inventory of freshwater fishes. Inventories were undertaken on the major hydrosystems of Grande-Terre and Loyalty Islands (Marquet et al. 2003). These inventories were completed between 2004 and 2008 by further specific studies, particularly in Panié Mountain, Forgotten Coast and Belep Islands. These recent surveys in Vanuatu and New Caledonia have permitted to add new records and to discover new species (Watson et al. 2001, 2002, 2005; Keith et al. 2004a, b, 2007a; Lord & Keith 2008). The purpose of this paper is to provide a description of Stiphodon mele n. sp., a freshwater goby known from Vanuatu and New Caledonia and to discuss about its larval dispersion. The genus Stiphodon Weber, 1895 has three haemal spines prior to the first anal pterygiophore, a narrow based pelvic disk and pelvic fin adherent to belly between fifth rays only, the tongue fused to the floor of the mouth and the dorsal tip of ascending process on premaxilla narrower than the process below. MATERIAL AND METHODS Methods follow those in Watson et al. (2005) and Keith et al. (2007a). All lengths of specimens are 472 A new species of goby (Teleostei, Gobiidae) from Vanuatu and New Caledonia expressed with a dial caliper in standard length (SL) to the nearest tenth of a millimetre (mm). Jaw length is measured from anterior tip of upper jaw to posterior edge of maxilla. Scales in a lateral series are counted from upper pectoral base and along the middle of the body laterally to the central hypural base. Body depth is measured from anterior base of second dorsal fin to belly, this measurement is taken only from males as females vary considerably from gravid to non gravid state. Transverse series back, refers to scales counted from the first scale anterior to second dorsal fin, in a diagonal manner, posteriorly and ventrally to the anal fin base or ventralmost scale. Transverse series forward, refers to scales counted from the first scale anterior to second dorsal fin, in a diagonal manner, anteriorly and ventrally to the centre of belly or ventralmost scale. Zigzag series, refers to scales on the narrowest region of the caudal peduncle counted from the dorsalmost scale to the ventralmost scale in a zigzag (alternating) manner. Abbreviations used to represent the cephalic sensory pore system follow Akihito (1986). The material cited in the present paper is deposited in the Muséum national d Histoire naturelle, Paris (MNHN). Diagrammatic illustrations of the head and the urogenital papilla are not provided in this work because there is no great morphological variation among the species so far described from streams flowing into the Pacific Ocean (Watson et al. 2005). Counts and morphometrics are summarized in the Appendix. SYSTEMATICS Family GOBIIDAE Linnaeus, 1758 Subfamily SICYDIINAE Gill, 1860 Genus Stiphodon Weber, 1895 Stiphodon mele n. sp. (Fig. 1) TYPE MATERIAL. Holotype: Vanuatu. Efate, Mele waterfall, 22.VII.2002, Keith and Keith coll., 27.2 mm SL (MNHN ). Paratypes: Vanuatu. Gaua, Solomul river, 21.VII.2005, Keith, Marquet and Keith coll., mm SL (MNHN ) Santo, Patunar s Doline, 14.IX.2006, Pouilly coll., 2, mm SL (MNHN ). Santo, Patunar resurgence, 15.IX.2006, Pouilly coll., mm SL (MNHN ). New Caledonia. North Province, Panie tributary, Keith et al. coll., mm SL (MNHN ). Remarks: seven specimens were collected from Vanuatu and New Caledonia totaling five males and two females with a size range of mm SL, largest male 27.2 mm SL. All specimens caught were adults and not juveniles. The metamorphosis was finished, the males were mature (urogenital papilla well differentiated and colourful specimens parading when caught) and the female gravid. COMPARATIVE MATERIAL. The new species is compared in text and tables with species of nearby areas in particular Stiphodon rubromaculatus Keith & Marquet, 2007, S. kalfatak Keith, Marquet & Watson, 2007, S. birdsong Watson, 1996, S. hydoreibatus Watson, 1999, S. surrufus Watson & Kottelat, 1995, S. tuivi Watson, 1995, S. astilbos Ryan, 1982 and S. sapphirinus Watson, Keith & Marquet, 2005 because these have pectoral rays and 9 segmented rays in the second dorsal fin. Material for S. rubromaculatus, S. birdsong, S. surrufus, S. hydoreibatus, S. tuivi and S. sapphirinus is that listed in Keith & Marquet (2007), and for S. kalfatak and S. astilbos in Keith et al. (2007a). ETYMOLOGY. The species is named mele to honour Mele waterfall in Efate where the first specimen was found (noun in apposition). DIAGNOSIS. A combination of characters distinguishes Stiphodon mele n. sp. The species has 13 pectoral rays, 9 segmented rays in the second dorsal fin and premaxillary teeth. There are no scales in predorsal midline. The most anterior scale along midline is below anterior part of second dorsal fin. Males have more and larger symphyseal teeth than females (2-4 vs. 2). The species has 3-7 scales in transverse backward series. The typical colouration of males is orange; the female is greyish to brownish. DESCRIPTION Number of premaxillary teeth, scale counts, and morphometrics in Stiphodon mele n. sp. and related species are given in Appendix (Tables 1; 2-5 and 6-15 respectively). Below, the holotype counts are given first followed in brackets, if different, by the paratypes counts. Dorsal fins VI-I,9, first dorsal fin separate from and of same height as second dorsal fin; spines not 473 Keith P. et al. elongate or filamentous. Anal fin I,10 and directly opposite to second dorsal fin. Pectoral fin counts 13 rays, uppermost rays extending beyond membrane but not appearing feathery or silky, lowermost 1 or 2 rays simple; fin oblong with posterior margin rounded. Caudal fin with 13 (13-14) branched rays, posterior margin rounded. Pelvic disc always with 1 spine and 5 stout and heavily branched segmented rays. Fifth rays joined together in their entire length forming a strong adhesive disc; disc adherent to belly between fifth rays only; between spines a strong fleshy frenum. Scales in lateral series 14 (14-21), those on caudal peduncle are ctenoid and they become cycloid below the second dorsal fin. Most anterior scale along midline below anterior part of second dorsal fin. Scales in transverse backward series 3 (3-7). Scales in transverse forward series 0 (0-7) with scales well developed at origin of second dorsal fin when present. Scales in zigzag series 6 (5-6). No scales in predorsal midline in males (0-1 in female). Females have a few small cycloid scales close to urogenital papilla and anus. Usually no scales on belly of males. Head, breast and pectoral base are without scales. Premaxillary teeth 36-41, fine and tricuspid, trident I-shaped with central cusp longer than lateral cusps. Dentary symphyseal teeth in males 3 (2-4) (females, 2), conical to canine I-shaped, stronger and larger. Cephalic sensory pore system always A, B, C, D, F, H, K, L, N and O; pore D is singular, all others are paired. Oculoscapular canal separated into anterior and posterior canals between pores H and K. Cutaneous sensory papillae developed over lateral and dorsal surfaces of head. Sexual dimorphism well developed with adult males always having bright orange or greyish coloration, presence of dots on dorsal fins and longer second dorsal and anal fins than female. Urogenital papilla in males somewhat rectangular with a rounded distal tip, while in female rectangular with tiny distal fimbriate projections. Colour in preservation Males. Background of body pale orange or yellowish; many scales along and above midline below second dorsal fin with ctenii generally blackish; belly with few brownish pigment. Background of head orange, greyish or yellowish; occipital region with brownish pigment; preoperculum behind eye with a small yellowish patch. First dorsal fin spines with 2 to 5 blackish dots evenly spaced; second dorsal fin spines and rays with 2 or 3 blackish dots evenly spaced. Caudal fin with slightly dusky brown crescent-shaped margin posteriorly; anal fin with a thin clear distal margin, below distal margin a band of brownish pigment; pelvic disk with few brownish pigment along distal margin. Females. Background of body yellowish; light dusky black band extending midlaterally from posterior to pectoral base ending as a spot posterior to hypural base. Another light dusky brown band extends from posterior to eye ending at upper caudal rays; belly and abdomen brownish. Background of head greyish; blackish brown band from snout and upper lip to central pectoral base. First dorsal fin clear except for fine brownish pigment along anterior and posterior edges of each spine; second dorsal fin clear, spine and rays with dusky brown pigment; caudal fin clear, rays without pigment; anal fin mostly clear; pelvic disk free of pigment; pectoral fin clear. Colour in life Males. Two different patterns. First one (Fig. 1), generally bright orange on side of head and body. Cheeks and nose orange or yellow. Caudal fi n hyaline with a reddish part at its base. The second pattern is more greyish on entire body. Posterior margin of scales blackish. All fins hyalines, some with dark dots: 2 to 5 black dots on each rays of first dorsal fin; 2 or 3 black dots on each rays of second dorsal fin. Females. Body generally hyaline or greyish; dusky markings as in preservation. Belly whitish to yellowish. COMPARISON Stiphodon mele n. sp. differs from S. rubromaculatus and S. surrufus because it has more premaxillary teeth (36-41 vs /25-36), lower scale counts in transverse back series (3-7 vs. 7-9/10-14) and in 474 A new species of goby (Teleostei, Gobiidae) from Vanuatu and New Caledonia FIG. 1. Stiphodon mele n. sp., holotype 27.2 mm SL (MNHN ), Efate, Mele waterfall, 22.VII.2002, Vanuatu, Keith and Keith coll. Photo: É. Vigneux. transverse forward series in males (0-1 vs. 1-4/0-12). It differs from S. sapphirinus, S. tuivi, S. hydoreibatus, S. kalfatak and S. astilbos, because it has lower scale counts (14-21 in lateral scales vs /23-39/23-35/30-34/24-29; 3-7 in transverse back series vs /10-14/9-10/8-9/9; 0-7 in transverse forward series vs. 7-15/12-19/10-14/7-8/12-16). Stiphodon mele n. sp. differs from S. birdsong in having less scales in transverse back series (3-7 vs. 8-15), more premaxillary teeth (36-41 vs. generally 28-37) and a shorter caudal peduncle in length (10-16 vs ). DISTRIBUTION Known from rivers of Gaua, Efate and Santo in Vanuatu, Mont Panié tributaries and Bélep Islands in New Caledonia. ECOLOGY Like other Sicydiinae, Stiphodon mele n. sp. is found in clear, high gradient streams with rocky bottom. It lives mainly on the riverbed, on top of rocks but it is also seen swimming in open water in the current between rocks or in large pools. This species was observed from 10 to 100 m high in altitude. KEY TO VANUATUAN AND NEW CALEDONIAN SPECIES OF STIPHODON WEBER, or 14 pectoral rays. Size 3.5 cm pectoral rays. Size 3.5 cm... Stiphodon atratus 2. Second dorsal fins with 10 branched rays... Stiphodon rutilaureus Second dorsal fins with 9 branched rays First and second dorsal fins with longitudinal black stripes... Stiphodon mele n. sp. First and second dorsal fins without longitudinal black stripes First dorsal fin of male non filamentous; less than 9 scales (or 9 scales) in transverse back series... 5 First dorsal fin of male filamentous; more than 9 scales in transverse back series Stiphodon sapphirinus 5. Less than 35 premaxillary teeth; scales in transverse forward series... Stiphodon astilbos More than 35 premaxillary teeth; 7 or 8 scales in transverse forward series Stiphodon kalfatak 475 Keith P. et al. COMMENTS ABOUT AMPHIDROMY AND REGIONAL DISPERSION In the Indo-Pacific region, insular river systems are colonised by Gobiidae, in particular Sicydiinae, with a life cycle adapted to the conditions in these distinctive habitats, which are young oligotrophic rivers subject to extreme climatic and hydrological seasonal variation. These species spawn in freshwater, the free embryos drift downstream to the sea where they undergo a planktonic phase, before returning to the rivers to grow and reproduce (Keith 2003; Keith et al. 2008), hence they are qualified as amphidromous (McDowall 2007). The practical details of their biological cycle and the parameters leading to such extreme evolution in amphidromous gobies are poorly known, despite the fact that these gobies contribute most to the diversity of fi sh communities in the Indo-Pacific insular systems, and have the highest levels of endemism (Keith et al. 2006; Lord & Keith 2008). The amphidromous life cycle is, for these species, the major way for dispersal and it allows them to colonise new rivers and new islands. But amphidromy also highlights the fact that there are factors which can limit or favour the dispersion of species and enabling them to be either endemic or cosmopolit. Among amphidromous gobies, the Sicydiinae Bleeker, 1874 subfamily comprises eight genera (Stiphodon [30 species]; Sicyopus Gill, 1863 [15]; Lentipes Günther, 1861 [12]; Cotylopus Guichenot, 1864 [2]; Sicyopterus Gill, 1860 [30]; Sicydium Valenciennes, 1837 [16]; Akihito Watson, Keith & Marquet, 2007 [2] and Parasicydium Risch, 1980 [1]), and is the most diversified of the group with nearly 110 species distributed in Indo-Pacific, West Africa, Central America and Caribbean areas (Keith 2003). All these genera have specific distribution and reflect a specific evolution in the areas concerned. Indeed, Sicydium is distributed throughout Caribbean, Central America and West Africa (Pezold et al. 2006), Sicyopterus is distributed in Indo-Pacific area from West Indian Ocean to East Pacific one (Keith et al. 2005a), Stiphodon, Sicyopus, Lentipes are distributed from East Indian Ocean to East Pacific (Watson et al. 2001, 2002; Keith & Marquet 2007), Cotylopus is restricted to West Indian Ocean (Keith et al. 2005b); Parasicydium is restricted to West Africa (Pezold et al. 2006) and Akihito, a recently described genus (Watson et al. 2007; Keith et al. 2007b) seems to be restricted to the West of Pacific Ocean. Within these genera we observe different distribution patterns (Keith et al. 2009). Among them, we can clearly distinguish a specific one sharing endemic species between New Caledonia and Vanuatu. The discovery of a new species of Stiphodon endemic to this region is very interesting from both biogeographical and conservation points of view. We assume that there are dispersion and exchange of larvae between New Caledonia and Vanuatu, owing to their amphidromous life cycle, depending on the species and the duration of the larval stage. Indeed, the only possibility for the dispersion of the species and the colonisation of islands is the marine planktonic larval phase. The duration of this planctonic stage varies from 91 to 265 days for several species of Sicydiinae of the Pacific and Caribbean region (Keith 2003; Murphy & Cowan 2007). The strength and direction of marine currents as well as the duration of the planktonic phase could influence the dispersion ability, the species distribution area, and the evolution of the group. In a recent study Keith et al. (2005a) have shown that an amphidromous species (Sicyopterus lagocephalus (Pallas, 1767)), prese
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