A deepwater threadfin, Polydactylus longipes (Perciformes: Polynemidae),from Vanuatu: new record from the South PacificbyHiroyuki Motomura* (1), Patrice Pruvost (2) & Romain Causse (2)RÉSUMÉ. - Présence d’un barbure longs-doigts, Polydactylus longipes (Perciformes: Polynemidae), au Vanuatu : nouveau signalement pour l’océan Pacifique sud.
Un spécimen de Polydactylus longipes, précédemment connu
par trois exemplaires types en provenance des Philippines, a étécollecté aux îles Vanuatu à une profondeur de 300-360 m. Ce spécimen est le premier signalement de P. longiceps en dehors desPhilippines, élargissant la zone de répartition de 5000 km dans lesud-est par rapport à la localité type. La profondeur de cette capturede P. longiceps est la plus importante recensée pour la famille. Deschangements morphologiques en relation avec la croissance allométrique de l’espèce sont également observés.
Key words. - Polynemidae - Polydactylus longipes - Vanuatu - Distribution - First record.
The family Polynemidae comprises eight genera with 43 species
and subspecies worldwide (Motomura, 2004a, 2004b; Motomura
and Tsukawaki, 2006; Lim et al., 2010). The Indo-Pacific speciesof Polydactylus Lacepède, the most speciose genus in the family,
were revised by Motomura (2002) who recognized 14 species asvalid and synonymized 12 nominal species. Subsequently, Lim etal. (2010) described a new species of Polydactylus from Sarawak,
Borneo. The genus Polydactylus is characterized by the pectoral-fin
insertion well below the midline of the side of the body, eye diameter relatively large, lip present on the anterior part of the lower jaw,

anal-fin base length less than head length, pectoral-fin base (including pectoral-filament base) length less than upper-jaw length, andspace separating the premaxillary tooth bands less than the width ofeach band (Motomura, 2004b).
The rarest species, P. longipes, was originally described byMotomura et al. (2001b) on the basis of three specimens (134159 mm standard length) collected off Mindanao Island, the Philippines. Since then, neither additional specimens nor photographsof P. longipes have been reported. However, a single large specimen of Polydactylus collected from Vanuatu by a bottom trawl at
300-360 m depth, during the Boa 1 Survey of the Tropical Deep
Sea Benthos Program, from 9 to 18 September 2005, led by theMuséum National d’Histoire Naturelle, Paris, was recently examined and confirmed as P. longipes. The specimen, herein described,represents the first record of the species from outside the Philippines.
Counts and measurements follow Motomura et al. (2001b)and Motomura (2004b). Pectoral-fin ray counts include only therays interconnected by a membrane, the lower free rays are considered separately. Counts of pectoral-fin filaments begin with theanterior (ventralmost) element. Standard, total and fork lengths areexpressed as SL, TL and FL respectively. The length of the pectoralfin base was measured from the base of uppermost pectoral-fin ray
to the base of the lowermost pectoral filament. The present specimen of P. longipes is deposited at the Muséum National d’Histoire
Naturelle, Paris (MNHN).
Polydactylus longipes
Motomura, Okamoto & Iwatsuki, 2001
(Fig. 2)English name: Long-limb Threadfin; French name: Barbure
longs-doigts.
Material examined
MNHN 2009-1448, 214.8 mm SL (240.5 mm FL, 293.2 mmTL), Big Bay, northern Espiritu Santo Island, Vanuatu, 15°06’05”S,166°52’07”E, 300-360 m depth, bottom trawl, RV Alis, 10 Sept.
2005.

Figure 1. - Records of Polydactylus longipes in the South Pacific. Circle andstar indicate capture localities of type specimens and the present specimen,respectively.

Description
Dorsal-fin rays VIII-I, 12; anal-fin rays III, 11; pectoral-fin rays
13; pectoral filaments 6 on each side of body; pelvic-fin rays I, 5;
pored lateral-line scales 55; scales above lateral line 6; scales belowlateral line 11; upper limb gill rakers 13, lower limb 20, total 33.
Body oblong, moderately compressed. Orbit diameter greater(1)	The Kagoshima University Museum, 1-21-30 Korimoto, Kagoshima 890-0065, Japan.
(2)	UMR BOREA 7208, Département “Milieux et peuplements aquatiques”, Muséum national d’Histoire naturelle, 43 rue Cuvier,75231 Paris cedex 05, France. [pruvost@mnhn.fr] [causse@ mnhn.fr]* Corresponding author [motomura@kaum.kagoshima-u.ac.jp]
Cybium 2011, 35(2): 159-161.

Polydactylus longipes from Vanuatu

Motomura et al.

Figure 2. - Polydactylus longipes from Vanuatu (MNHN 2009-1448, 214.8 mm SL).

than both snout length and interorbital width. Maxilla covered withscales; posterior margin of maxilla extending slightly beyond a vertical through posterior margin of adipose eyelid; depth of posterior
portion of maxilla less than eye diameter; lower lip well-developed.
Villiform teeth on vomer, palatines and ectopterygoids; width ofpalatine plate much wider than that of ectopterygoid. All pectoral-fin rays unbranched; posterior tip of pectoral fin just short of avertical through posterior tip of depressed pelvic fin. First pectoral
filament shortest, first and second filament not reaching to posterior tip of depressed pelvic fin; third filament extending beyond
anus; fourth filament reaching to midpoint of anal-fin base; fifth
filament longest, extending well beyond midpoint of caudal peduncle; sixth pectoral filament extending slightly beyond midpoint ofcaudal peduncle. Thickness of second to fourth spine bases in firstdorsal fin similar. Length of second dorsal-fin base slightly longer
than that of anal-fin base. Distance between origins of pelvic andanal fins less than head length. Lateral line simple, extending fromupper end of gill opening to upper end of lower caudal-fin lobe.
Swimbladder simple, well developed.
Morphometrics
Head length 33.8% of SL; body depth at first dorsal fin origin
30.3; body depth at second dorsal fin origin 28.6; body width atpectoral fin base 13.8; snout length 6.1; eye diameter 8.1; orbit
diameter 10.4; interorbital width 8.8; postorbital length 19.1;
upper-jaw length 16.8; pre-first dorsal-fin length 37.7; pre-second
dorsal-fin length 65.2; pre-anal-fin length 69.3; pelvic-fin origin
to anal-fin origin 44.8; second dorsal-fin base length 14.6; anal-finbase length 12.9; longest pectoral-fin length 26.4; longest pectoralfilament length 72.4; pectoral-fin base including pectoral-filamentsbase 8.9; longest pelvic-fin ray length 18.2; longest first dorsal-fin
spine length 18.2; second dorsal-fin spine length 10.5; longest analfin spine length 10.5; caudal-peduncle length 22.0; caudal-peduncle
depth 12.1; upper caudal-fin lobe length 36.5; lower caudal-fin lobe
length 32.6.
Colour of preserved specimen
Head and body dark gray dorsally, brown ventrally; opercularregion distinctly black. First dorsal fin black anterodistally, whitish posteriorly. Pectoral-fin membranes semitransparent, melanophores scattered on rays; pectoral filaments gray. Posterior soft raysof second dorsal and anal fins whitish, remainder dark gray. Caudal
fin gray, black marginally.
160Remarks
Diagnostic characters of the Vanuatu specimen agreed withthose given for P. longipes by Motomura et al. (2001b); viz., 13
pectoral-fin rays, all rays unbranched; 6 pectoral filaments, upper 2filaments extending beyond midpoint of caudal peduncle; 55 pored
lateral-line scales; 6 scale rows above lateral line, 11 below; vomerine teeth present; and grayish-black body. However, the former
specimen differed slightly from the type series in having relatively
shorter fin lengths, including pectoral-fin length 26.4% of SL (vs27.8-29.1% in the latter), longest first dorsal-fin spine length 18.2%(vs 23.0-24.4%), upper caudal-fin lobe length 36.5% (vs 40.144.4%) and lower caudal-fin lobe length 32.6% (vs 35.0-40.2%). In
addition, the longest pectoral filament in the Vanuatu specimen was
the fifth (sixth in the type series). These minor morphometric differences appear to reflect changes related to allometric growth, thepresent specimen (214.8 mm SL) being much larger than the typeseries (134.1-158.9 mm SL).
Polydactylus longipes can be easily distinguished from othercongeners by having 6 pectoral filaments, the 2 uppermost extending beyond the middle of the caudal peduncle, but not reaching to
the caudal-fin base (Motomura, 2004b; Lim et al., 2010). Detailed
comparisons of P. longipes with other congeners were given by
Motomura et al. (2001b), Motomura (2004b) and Lim et al. (2010).
The Vanuatu specimen represents the first record of P. longipesfrom outside the Philippines (an approximately 5000 km southeastward range extension), suggesting that P. longipes is widely distributed in the tropical western Pacific.
Since the type specimens of P. longipes, purchased at a fish
market in Davao, Mindanao Island, lacked data for the depth ofcapture, the habitat of the species was unknown. However, thecapture depth of the Vanuatu specimen (300-360 m) indicates thatP. longipes is a deepwater species, being the deepest occurring
member of the family (usually less than 50 m, rarely 100-150 m;
Motomura, 2004b).
The pectoral fins of polynemids are their most distinctive
feature, being divided into an upper part with the rays joined bymembranes and a lower part with 3 to 16 separate rays (pectoralfilaments), which have been considered to operate as a sense organ(probably acting as a substitute for eyesight), enabling polynemids to search for food in muddy water (Motomura et al., 2002;
Motomura, 2004b). In particular, species of Parapolynemus Feltes
and Polynemus Linnaeus, generally occurring in freshwater rivers
and estuaries, have extremely long pectoral filaments (exceeding
their total length) and extremely small eyes (2-5% SL) (Motomura,2004b). However, some species of Polydactylus occurring in clear
Cybium 2011, 35(2)Motomura et al.

Polydactylus longipes from Vanuatu

open waters, like P. sexfilis Valenciennes, have short pectoral filaments (not reaching to the anal-fin origin in S. sexfilis) and largeeyes (8-11% of SL in S. sexfilis) (Motomura et al., 2001a). The
unique specialization of long pectoral filaments (reaching to themiddle of the caudal peduncle) and large eyes (8.1-9.2% SL) foundin P. longipes appear to have arisen as an adaptation to the deepwater habitat of the species.
Acknowledgments. - We thank Philippe Béarez, Claude Ferrara, Zora
Gabsi, Anne Previato, and all other staff of the Département “Milieux etpeuplements aquatiques” at the Muséum national d’Histoire naturelle for
their kind assistance. We greatly appreciated comments on the manuscript
by Graham S. Hardy (Ngunguru, New Zealand). The first author’s visit
to Paris for two months in 2010 was supported by the Muséum nationald’Histoire naturelle.

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Accepté pour publication le 17 novembre 2010.

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