Acinocheirodon melanogramma Malabarba & Weitzman 1999

Acinocheirodon melanogramma is distributed in the São Francisco and Jequitinhonha River basins, Brazil (Malabarba & Weitzman, 1999; Malabarba, 2003).

This species inhabits clear freshwater streams, in general with moderate current.

There is little information about the life history and behavior of Acinocheirodon melanograma. It is known that A. melanogramma is an inseminating species due to the observation of spermatozoa inside the ovary of females (Burns et al., 1997), however fertilized eggs and embryos were never observed. The males in a certain stage of maturation start to develop several sexually dimorphic features. Some of them are very common among the characids, like the presence of hooks in the pelvic- and anal-fin rays. Other differentiations are uniquely found in this species, like the presence of hooks on some of the caudal-fin rays associated with hypertrophied caudal tissue, in the shape of flaps (Malabarba & Weitzman, 1999).

Acinocheirodon melanogramma is diagnosed from all characids by the presence of one row of pedunculated teeth in the upper and lower jaws, presence of pseudotympanum, absent of humeral spot, lateral line completely perforated and the presence of hooks and hypertrophied tissue on the caudal fin.

Maximum size registered for a male with 38 mm of standard length, from the tip of the snout to the base of the caudal fin (Malabarba & Weitzman, 1999).

This species present the body slightly elongated, terminal to subterminal mouth. Likewise all members of the subfamily Cheirodontinae, it only presents one tooth row in the premaxilla and dentary. The teeth are pedunculated with several cusps. There is no humeral spot and a pseudotympanum instead is present on the humeral region. Acinocheirodon melanogramma presents a lateral line completely pored and no scales covering the caudal-fin lobes. The body does not present any conspicuous coloration, except a dark spot on the end of the caudal peduncle and a slightly yellowish caudal fin.