Astyanax ajuricaba

biology_ecology

Ecological notes. The type-locality of Astyanax ajuricaba is a black-water, terra-firme forest stream about 4 - 5 meters wide and 0.5 - 1.0 meters deep, with a predominantly sandy bottom. Specimens MZUSP 92252 were collected in a large oxbow lake of the rio Tiquié. According to field notes by P. Vanzolini, specimens from the igarapé Centrinho, in the rio Tapajós basin (MZUSP 18280), were collected in a small terra-firme stream, a habitat apparently similar to the type-locality.

Astyanax ajuricaba: a new species from the Amazon basin in Brazil (Characiformes: Characidae)

description

Description. Morphometric data for Astyanax ajuricaba is summarized in Table 1. Body elongated, compressed laterally. Largest specimen examined 95.2 mm SL. Greatest body depth immediately anterior to dorsal-fin origin. Dorsal profile of head slightly convex from snout tip to vertical through anterior nostril, and straight from that point to tip of supraoccipital spine. Predorsal profile of body slightly convex, posteroventrally slanted and straight from dorsal-fin origin to adipose-fin origin, slightly concave between latter point and origin of anteriormost dorsal procurrent caudal-fin ray. Ventral profile of head and body convex from lower lip to anal-fin origin; body profile along anal-fin base straight, posteroventrally inclined, and slightly concave between analfin terminus to anteriormost ventral procurrent caudal-fin ray. Jaws equal, mouth terminal; posterior terminus of maxilla reaching vertical through anterior third of orbit. Premaxillary teeth in two rows, with midcentral cusp more developed than remaining cusps; outer teeth row with 4 (6), 5 * (44), or 6 (1) tricuspid teeth; inner tooth row with 4 (5), 5 * (41) or 6 (5) tri- to pentacuspid teeth. Maxillary with 1 (5) or

Astyanax ajuricaba: a new species from the Amazon basin in Brazil (Characiformes: Characidae)

diagnosis

Diagnosis. Astyanax ajuricaba can be diagnosed from all congeners, and in fact from all remaining characids by its unique color pattern consisting of the combination of presence of a conspicuous, narrow dark midlateral stripe, a single elongated humeral spot, and upper caudal-fin lobe and middle caudal-fin rays dark, with a clear, rounded ocellated spot present dorsally at anterior third of caudal-fin lobe. See the Discussion for further details.

Astyanax ajuricaba: a new species from the Amazon basin in Brazil (Characiformes: Characidae)

distribution

Distribution. Astyanax ajuricaba is known from the upper rio Negro basin at the rio Tiquié, a large tributary from the rio Uaupés, the middle and lower rio Negro areas at Santa Isabel do Rio Negro and Anavilhanas archipelago, respectively, and the lower rio Tapajós basin, Brazil. Géry (1992) recorded Astyanax ajuricaba (as Astyanax sp.) from the lago do Castanho (c. 3 ° 23 ’ S 60 ° 13 ’ W), a large lake connected to the better-known lago Janauacá, both of which are situated at the floodplains of the rio Solimões, in the central Amazon basin (Fig. 3).

Astyanax ajuricaba: a new species from the Amazon basin in Brazil (Characiformes: Characidae)