Microsternarchus javieri, a new species of weakly electric fish (Gymnotiformes: Hypopomidae, Microsternarchini) from the Negro River basin, Amazonas, Brazil

Abstract

Here we describe a new hypopomid species, Microsternarchus javieri n. sp., encountered in flooded savanna streams of the Branco River and in terra-firme streams in the mid-and lower portions of the Negro River basin. We compared this new species with M. bilineatus from the San Bartolo River, Venezuela, and M. brevis from the upper portion of the Negro River. We also compared this new species with two recently described species in the genus Microsternarchus, M. longicaudatus and M. schonmanni. We examined morphometrics, anatomical characters, DNA barcode distances for the COI (cytochrome C oxidase subunit I) gene, and electric organ discharge (EOD) parameters. We diagnosed M. javieri n.sp. based on variation in maximum body depth, eye diameter, caudal vertebral counts, number of anal fin rays, and the shape of the maxillae. The average intra-specific genetic distance (K2P) in M. javieri n.sp. was 0.83%, whereas the average inter-specific genetic distance to M. brevis was 12.45%, and to other hypopomids ranged from 17.21 to 21.54%. When comparing EOD waveforms of the new species with M. brevis, we found differences in repetition rate, the ratio between the first and second phase areas, and the polarity balance. The description of M. javieri n. sp. increases to five the number of species in the genus.