Notes ichtyologiques / Ichthyological notes
Description of four small reef fishes from Ecuador: Oxycirrhites typus (Cirrhitidae), Acanthemblemaria balanorum (Chaenopsidae), Arcos decoris (Gobiesocidae) and Lythrypnus dalli (Gobiidae) by Philippe BÉAREZ (1), Jean-Thomas BUJARD (2) & Roberto CAMPOVERDE (2)
RÉSUMÉ. - Description de quatre petits poissons de récif de l’Équateur : Oxycirrhites typus (Cirrhitidae), Acanthemblemaria bala norum (Chaenopsidae), Arcos decoris (Gobiesocidae) et Lythryp nus dalli (Gobiidae). Oxycirrhites typus, Acanthemblemaria balanorum, Arcos deco ris et Lythrypnus dalli sont décrits suite à une prospection en plongée du récif bordant l’îlot El Pelado sur le littoral sud-équatorien. Leur capture dans l’extrême limite sud de la province panaméenne permet d’étendre notablement leur répartition géographique. Une description plus détaillée est fournie pour A. decoris en raison de son caractère atypique. Key words. - Chaenopsidae - Cirrhitidae - Gobiesocidae - Gobiidae - Oxycirrhites typus - Acanthemblemaria balanorum - Arcos decoris - Lythrypnus dalli - Ecuador - TEP - Reef fishes. The ichthyofauna of continental Ecuador is much better known now than it was twenty years ago (Massay, 1983; Béarez, 1996; Jiménez-Prado and Béarez, 2004), but much still remains to be done, especially concerning the small and cryptic shallow water fauna and the medium depth (150-300 m) benthic fauna. The use of diving equipment and ichthyocides for underwater prospection and collection provide new results (Collette et al., 2003) and allow the increase of our knowledge of the small cryptic ichthyofauna. The fish captures we report here include such small tropical reef species, previously unknown from Ecuador (Jimenez-Prado and Béarez, 2004) The families Gobiesocidae, Cirrhitidae, Chaenopsidae, and Gobiidae comprise mainly typical shallow water bottom-dwellers on rocky or coral reefs, including tide pools. While clingfishes and gobies are found worldwide in tropical to temperate seas, cirrhitids are dominantly an Indo-Pacific family, and tube blennies are largely restricted to the neotropics. In the tropical eastern Pacific, these families are represented by 46 (including brackish and freshwater species), 80 to 90, 3, and 33 species, respectively (Briggs, pers. com., 2004; Allen and Robertson, 1994; Hastings, 2000).
Figure 1. - Map of Ecuador showing the locality of capture: Islet El Pelado. [Carte de l’Équateur montrant la localité de capture : îlot El Pelado.]
the Muséum national d’Histoire naturelle (MNHN, Paris, France). The taxonomic classification follows Nelson (1994). The methodology used for counts and measurements follows Hubbs and Lagler (1947), and Briggs (1955). Meristic counts for A. decoris and Lythrypnus dalli were made from X-rays. Common measurements are abbreviated as follows: total length (TL); standard length (SL); head length (HL); head width (HW). The nomenclature of scientific names follows the Eschmeyer’s on-line Catalog of Fishes (2006). RESULTS
MATERIALS AND METHODS All specimens examined were captured close to San Pedro, Guayas, around the small island called “El Pelado” (Fig. 1) with Quinaldine and the help of hand nets during scuba dives at depths of 8 to 35 m. While trying to extract tube blennies (Acanthemble maria spp.) from their crevices in coral and barnacles, specimens of the clingfish came out (Arcos decoris) and were also trapped in the scoop net. The specimens are deposited in the fish collection of
Oxycirrhites typus Bleeker, 1857 Material examined. - MNHN 2004-0546, 86 mm SL (103.5 mm TL), collected on 21/09/2003, 8-12 m, Islet El Pelado, San Pedro, Guayas, Ecuador (1°56’S, 80°47’W). Distribution. - An Indo-Pacific cirrhitid known from Red Sea to eastern Pacific, north to southern Japan and Hawaii, south to New Caledonia (Myers, 1999). In the tropical eastern Pacific it is known from Baja California to Gorgona Island (southern Colombia), and Galápagos islands (Rubio et al., 1987; Bussing and Lavenberg,
(1) UMR 5197, Département “Écologie et gestion de la biodiversité”, Muséum national d’Histoire naturelle, 55 rue Buffon, 75231 Paris CEDEX 05, FRANCE. [
[email protected]] (2) Darwinvest Cia. Ltda., PO Box 09-06-6197, Guayaquil, ECUADOR. [
[email protected]] Cybium 2007, 31(4): 477-479.
Four small reef fishes from Ecuador 1995). Its range is now extended to southern Ecuador. Description. - Oxycirrhites is a monotypic genus. Our specimen is easily recognizable for its elongate snout, its length 2 in HL; a slender body, its depth 4.5 in SL. D X, 13; A III, 7; P 14 (the lower 5 unbranched and enlarged). Lateral line scales 52. The longnose hawkfish is usually found at depths greater than 30 m, and to at least 100 m (Morris and Morris, 1967; Myers, 1999), but has been collected at only 4-5 m in the Gulf of California (Thomson et al., 2000). Its habitat seems to be in tight association with gorgonians and black coral, as our observations in Ecuadorian waters confirm. Acanthemblemaria balanorum Brock, 1940 Material examined. - MNHN 2004-0540, 4 specimens 32-44.5 mm SL (37-51 mm TL), collected on 21/09/2003, 8-12 m, Islet El Pelado, San Pedro, Guayas, Ecuador (1°56’S, 80°47’W), (Fig. 2). Distribution. - Tropical eastern Pacific endemic chaenopsid species, known from the Gulf of California to southern Mexico, Panama, and Gorgona Island (Hastings and Robertson, 1999). Range is herein extended to southern Ecuador. Description. - The genus Acanthemblemaria is the most characteristic genus of chaenopsid family and its members are well known for their prominent cranial spination. The cranial spines and pore patterns of A. balanorum easily distinguished it from other members of the genus. The frontal bones of this species have conspicuous high and thick spines on head, often club-shaped in large individuals (Rosenblatt and McCosker, 1988: Fig. 2E). Arcos decoris Briggs, 1969 Material examined. - MNHN 2004-0542, 23 mm SL, collected on 21/09/2003, 8-12 m, Islet El Pelado, San Pedro, Guayas, Ecuador (1°56’S, 80°47’W). Morphometric and meristic data are given below (Fig. 3). Distribution. - Tropical eastern Pacific endemic gobiesocid species, known from Panama (Allen and Robertson, 1994) and Colombia, including Isla Malpelo (McCosker and Rosenblatt, 1975) and Isla Gorgona (Schoppe and Werding, 1996). Its range is herein extended to southern Ecuador. Description. - Dorsal rays 8, anal rays 8, pectoral rays 23, and caudal rays 10. Body well depressed, depth 5.2 in SL. Snout steep and slightly rounded in lateral outline, 3.2 in HL. Posterior nostril tubular and located just behind anterior edge of eye. Anterior nostril tubular with a large, bifid dermal flap extending from its posterior margin. Teeth in lower jaw in two rows; in the outer row, a pair of large incisors in front followed on each side by two small conical teeth and then a well-developed canine; inner row consists of small conical teeth. Teeth in upper jaw irregular, conical and forming a cluster toward the front with a small canine on each side. Eye 0.5 in bony interorbital space and 2.8 in HL. HL 2.4 and HW 2.8 in SL. Shallow lobes on chin but no papillae on head, none on upper lip margin, and none on snout above centre of premaxillary groove. Disc length 3.1 in SL. Disc regions A and B each with about 8 rows of flattened papillae across its width. Each part of disc region C bears 3-4 longitudinal rows of papillae. Upper attachment of gill membrane opposite dorsal origin of pectoral fin. Upper attachment of axial, dermal flap opposite 6th pectoral ray. Fleshy pad on lower pectoral base poorly developed and without a free posterior margin. Depressed tip of anal fin lies well anterior to caudal base. Anus closer to anal fin origin than to rear margin of disc. Caudal peduncle long, its depth 1.5 in its length. Coloration. - Life colour: body ground colour pale. Four yellowish bars are visible on the sides. Dorsal part of the head slightly pinkish. Gill cover translucent, with the red of the gills visible externally.
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BÉAREZ ET AL. Underside of body pale. All fins pale or slightly yellowish. Colour in alcohol: general coloration cream mixed with pink. Yellowish bars are replaced by pink. The head is mostly pink and the circumference of the eyes is mauve, wine coloured. Underside of body cream. The strange pattern of the papillae on the disc as well as the coloration of our odd clingfish made us hesitate on its generic status. However we recognized it as a specimen of A. decoris, although it is certainly anomalous. Lythrypnus dalli (Gilbert, 1890) Material examined. - MNHN 2006-1224, 2 specimens 22-26 mm SL, collected on 11/05/2005, 30-35 m, Islet El Pelado, San Pedro, Guayas, Ecuador (1°56’S, 80°47’W). Distribution. - Tropical eastern Pacific endemic gobiid species, known from central California to Panama (Eschmeyer and Herald, 1983; Bussing, 1990). Its range is herein extended to southern Ecuador.
Figure 2. - Acanthemblemaria balanorum, El Pelado Island, Guayas, Ecuador. Head detail showing the specific cranial spination. HL = 10.2 mm. [Détail de la tête montrant l’ornementation spécifique du crâne.]
Figure 3. - Arcos decoris, El Pelado Island, Guayas, Ecuador. Dorsal and ventral views. TL = 27 mm. [Vues dorsale et ventrale.]
Cybium 2007, 31(4)
BÉAREZ ET AL.
Four small reef fishes from Ecuador
Description. - Lythrypnus is a tropical eastern Pacific gobiid genus including few species. Our specimen clearly belongs to the species L. dalli. It is recognizable by its coloration, its low predorsal crest on head, and the following meristics: D VI+I, 16-17; A I, 13-14; P 18-20. These features agree with the ranges given by Bussing (1990). The bluebanded goby inhabits rocky reefs where it is usually found from intertidal pools to at least 75 m (Allen and Robertson, 1994). Its habitat seems to be in tight association with gorgonians and black coral, as our observations in Ecuadorian waters confirm. Coloration. - Bright red-orange with 2 narrow blue crossbars on head and 5 on body. DISCUSSION All the species were found over rocky reefs covered by gorgonians, coral, and barnacles. Tube blennies (Acanthemblemaria spp.) especially frequent this habitat and it seems that the clingfish A. decoris also may live in empty barnacle shells. It has already been observed that the latter sometimes hides underneath sea urchins, especially in Echinometra vanbrunti A. Agassiz, 1863 boreholes, but also in association with Diadema mexicanum A. Agassiz, 1863 (Schoppe & Werding, 1996). The bluebanded goby is also said to cohabit with the sea urchin E. vanbrunti (Allen and Robertson, 1994). Other benthic reef fish species captured along with the ones presented herein were Malacoctenus tetranemus (Cope, 1877), Acanthemblemaria hancocki Myers & Reid, 1936, and Elacatinus puncticulatus (Ginsburg, 1938). Acanthemblemaria hancocki is known to share its habitat with A. balanorum at Gorgona Island (Hastings and Robertson, 1999). Even if already mentioned for Ecuador (Jiménez Prado and Béarez, 2004), none of these species had been sighted or captured by us before. The range of the four species described above is extended to at least 5 degrees of latitude to the South. The fact that scuba diving collections have rarely been practised in Ecuador and the notable cryptic behaviour of these species could explain why they passed unperceived until now. The wide distribution of A. balanorum in the tropical eastern Pacific, despite several faunal gaps along the mainland, is surprising when we consider the reduced dispersal abilities of the chaenopsids (Hastings, 2000). This also suggests that A. balanorum is probably not a new migrant in Ecuadorian waters, but is rather an uncommon and unnoticed resident. Acknowledgements. - We are indebted to Jack Briggs for his help in identifying our odd clingfish and for his comments on our draft. Our thanks to Phil Hastings for confirming the identification of A. balanorum. Financial support: grant to PB from the PPF “Structure et évolution des ecosystems” of the MNHN and Darwinwest Cia. Ltda.
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