Bryconops melanurus

Bryconops melanurus reaches a maximum total length of about 13.2 cm (5.2 in), which puts it on the larger side of the genus Bryconops. The head is slender, with a pointed snout, and B. melanurus lacks a humeral spot of the kind frequently seen in congeners (such as B. humeralis and B. inpai). B. melanurus shares aspects of its jaw structure, which is rather lengthened, with B. inpai, B. affinis, and B. giacopinii. (This was used to place giacopinii in the genus Bryconops instead of its originally described Autanichthys.) Bryconops melanurus is a silvery, slender fish with a darker back. The caudal fin has distinctive markings, but lacks a well-formed ocellus (eyespot). There is a dark stripe about the width of the pupil that veers from the center of this fin up towards the dorsal lobe, and the caudal-fin margins are dusky. The rest of the fin is either light in pigment (usually yellowish) or entirely clear. Bryconops melanurus has noted morphological similarities with congeners B. transitoria and B. gracilis, but can be differentiated based on morphometric specifics and differences in fin structure; for instance, B. transitoria has 23-27 anal-fin rays, whereas B. melanurus has 28–29. B. melanurus is also known to be similar to B. …

The type locality of B. melanurus is Suriname, but no specific river was given in the original description. Specimens have been cited from the Caraipé, Curuá, Madeira, and Moju rivers in modern accounts, as well as the Tapajós. Within this range, it seems to demonstrate no preference for any one biotope in particular, but does prefer living in groups.

Diet. Bryconops melanurus feeds primarily on insects. This is in line with the rest of the genus, members of which are largely invertivores, with a few noted herbivores on the list. Specific dietary habits are unclear, but may be similar to habits of congeners B. inpai and B. magoi, which feed on terrestrial insects that are either washed into the river or that fall from trees hanging above.