Apteronotus eschmeyeri

distribution

Distribution: Magdalena River basin and Cauca River, Colombia (de Santana et al., 2004; Maldonado-Ocampo, de Santana, 2005).

Checklist of Gymnotiformes (Osteichthyes: Ostariophysi) and catalogue of primary types

biology_ecology

Dahl (1971) reports that A. eschmeyeri is eaten by native people. However, in a recent survey to the Magdalena Basin, JAM talked with local fishermen in Honda, and they did not report any commercial use for this species. It is accidentally captured with gills nets used for commercial fishes (e. g., Prochilodus magdalenae), but then is returned to the water. Size and sexual dimorphism. We examined specimens of A. eschmeyeri up to a maximum size of 303.7 mm (male). Dahl (1971) reported a maximum size of 400.0 mm for this species. It is possible that this species shows secondary sexual dimorphism with relation to head morphology. Sexual dimorphism in head morphology has been reported in several apteronotid species (Cox-Fernandes, 1998; Cox-Fernandes et al., 2002; de Santana, 2003). However, the small number of specimens of A. eschmeyeri does not allow a more detailed analysis of sexual dimorphism.

Apteronotus eschmeyeri, a new species of ghost knifefish from the Magdalena Basin, Colombia (Gymnotiformes: Apteronotidae).

description

Description. Morphometrics for holotype and paratypes are presented in Table 1. Body proportions and pigmentation are illustrated in Figs. 1 and 2. Body laterally compressed, with greatest body depth at abdominal cavity or just posterior to this region. Dorsal profile straight. Lateral line extending to tail, absent on caudal fin. First perforated scale above pectoral-fin origin. Head laterally compressed, widest at opercular region and deepest at dorsal region; bones of cranium not reticulated. Head profile straight in males and slightly convex in females. Snout straight and long in males, slightly convex in females. Mesethmoid short and narrow, its anterior tip reduced, flexed ventrally, and concave. Lateral ethmoid present, ossified, small and slender, shaped as a tube. Eyes small, laterally situated on head, completely covered by thin membrane. Premaxilla of moderate size, bearing two irregular rows of teeth, with 10 to 11 conical teeth. Maxilla crescent-shaped, with ossified anterodorsal head and anteroventral shelf; ventral margin of its descending blade curved. Dentary longer than deep, with three to four irregular rows of teeth. Anguloarticular elongated. Mouth large, termi

Apteronotus eschmeyeri, a new species of ghost knifefish from the Magdalena Basin, Colombia (Gymnotiformes: Apteronotidae).

diagnosis

Diagnosis. Apteronotus eschmeyeri is included in Apteronotidae by the presence of a dorsal mid-saggital electroreceptororgan (dorsal thong of Mago-Leccia, 1994; dorsal organ of Albert, 2001) and a caudal fin (Mago-Leccia, 1994; Albert & Campos-da-Paz, 1998; Albert, 2001). The new species shares the following diagnostic features within the subfamily Apteronotinae (Albert & Campos-da-Paz, 1998; Albert, 2001): gape of mouth large, extending to edge of eyes; maxilla rhomboid in lateral view; anterior surface of mesethmoid concave and lateral process of ventral ethmoid robust (Albert, 2001). Apteronotus eschmeyeri was included in Apteronotus by the presence of two of five synapomorphies proposed by Albert (2001): body surface deep brown or black with a white middorsal stripe and white mental and caudal patches, and elongate posterior limb of anguloarticular. The new species can not be included in any previous species-group proposed by Albert (2001). Apteronotus eschmeyeri can be distinguished from congeners by the following combination of features: 1, blotchy coloration on body (vs. even brown or black coloration in most Apteronotus, except A. cuchillo and A. magdalenensis, which have b

Apteronotus eschmeyeri, a new species of ghost knifefish from the Magdalena Basin, Colombia (Gymnotiformes: Apteronotidae).