Corydoras tukano

biology_ecology

Habitat and ecological notes. The rio Tiquié, type-locality of C. tukano, is a blackwater river. At the exact type locality the bottom is sandy, with a moderate amount of vegetal debris. Corydoras tukano also was collected at sites with predominantly clay substrates. James (2003 a, b) related that in captivity specimens of this species (identified by him as Corydoras sp. cf. reynoldsi) lay several scattered clutches of large eggs (2.2 mm in size). See also “ Discussion ”, below.

Corydoras tukano, a new species of corydoradine catfish from the rio Tiquié, upper rio Negro basin, Brazil (Ostariophysi: Siluriformes: Callichthyidae)

description

Description. Morphometric data presented in Table 1. Head compressed with slightly convex dorsal profile; roughly triangular in dorsal view (Fig. 4). Snout rounded. Head profile convex from upper lip to horizontal through the anterior nares; slightly convex from that point to tip of parieto-supraoccipital expansion. Dorsal profile of body slightly convex from tip of parieto-supraoccipital expansion to last dorsal-fin ray. Postdorsal-fin body profile slightly concave to adipose-fin spine; markedly concave from this point to caudal-fin base. Ventral profile of body slightly convex from isthmus to analfin origin. Profile markedly concave from first anal-fin ray to caudal-fin base. Body roughly cylindrical in cross section at pectoral girdle, gradually becoming more compressed toward caudal fin. Eye round, located dorso-laterally on head; orbit delimited dorsally by frontal and sphenotic, ventrally by infraorbitals. Anterior and posterior nares proximal, only separated by flap of skin. Anterior naris tubular. Posterior naris close to anterodorsal margin of orbit, separated from it by distance equal to naris diameter. Mouth small, subterminal, width nearly equal to bony orbit diameter.

Corydoras tukano, a new species of corydoradine catfish from the rio Tiquié, upper rio Negro basin, Brazil (Ostariophysi: Siluriformes: Callichthyidae)

diagnosis

Diagnosis. Corydoras tukano can be distinguished from all its congeners, except C. reynoldsi Myers & Weitzman and C. weitzmani Nijssen, by its color pattern consisting of a light ground coloration, with three dark, large, roughly rectangular blotches: the first one (“ mask ”) on the head, across the eye; the second one on the trunk at the level of dorsal fin; and the third one on the trunk at the level of the adipose fin. It can be distinguished from C. reynoldsi by the larger dark blotches, which in C. tukano are broad, with the trunk blotches extending across 5 - 6 series of lateral plates. In C. reynoldsi, the first trunk blotch (i. e., at the level of dorsal fin), is a discrete, verticallyelongated bar, and the second trunk blotch extends only across 2 - 3 series of lateral plates (see Myers & Weitzman, 1960: fig. 2; Nijssen & Isbrücker, 1983 a: fig. 10). See “ Discussion ” for additional evidence for the recognition of both as distinct species. Corydoras tukano may be distinguished from C. weitzmani by the presence of a dark blotch or saddle on the dorsal portion of dorsolateral plates, just posterior to last dorsal-fin ray, that extends from the 9 th to the 13 th plate (vs. a

Corydoras tukano, a new species of corydoradine catfish from the rio Tiquié, upper rio Negro basin, Brazil (Ostariophysi: Siluriformes: Callichthyidae)

distribution

Distribution. Known only from the rio Tiquié and its tributaries, as the igarapé Cabari. Rio Tiquié is a tributary of the rio Uaupés, in the upper rio Negro basin, Amazonas, Brazil, near the Brazilian / Colombian border (Fig. 6). Most of the specimens studied were collected in the upper rio Tiquié, in the area between Pari-Cachoeira (0 ° 15 ’ N, 69 ° 46 ’ W) and Caruru (0 ° 16 ’ N, 69 ° 54 ’ W). One sample (MZUSP 65689) was collected near Cunuri (0 ° 12 ’ N, 69 ° 22 ’ W), a downstream locality not intensively sampled by the second author or associates. According to Tukano and Tuyuka fishermen, Corydoras tukano occurs thorough the rio Tiquié basin, from its lower course upstream to Caruru, where a major waterfall about 8 m high, the Cachoeira do Caruru, effectively separates the downstream ichthyofauna from the upper section of this river. Again according to Tukano and Tuyuka fishermen, C. tukano is absent upstream of this waterfall. In fact, despite considerable time and effort spent in apparently suitable sites, the second author was unable to collect any C. tukano upstream of the Cachoeira do Caruru.

Corydoras tukano, a new species of corydoradine catfish from the rio Tiquié, upper rio Negro basin, Brazil (Ostariophysi: Siluriformes: Callichthyidae)