Redescription of Moenkhausia melogramma (Characiformes: Characidae), a poorly known tetra from the western Amazon basin

Isabel M Soares,Rafaela P Ota,Ricardo C Benine,Flávio C T Lima

doi:10.1590/1982-0224-2020-0025

Abstract

ABSTRACT Moenkhausia melogramma is herein redescribed, based on the examination of the holotype plus additional specimens from the western Amazon basin in Brazil, Colombia, Peru, and Ecuador. Moenkhausia melogramma shares with M. collettii, M. conspicua, M. copei, M. venerei, and M. flava a broad dark longitudinal stripe across the eye, and a well-defined dark stripe on the anal-fin base. It can be promptly distinguished from these species by having two humeral blotches. Additionally, we provide comments on the putative relationships of Moenkhausia melogramma with the aforementioned congeners and the Hemigrammus lunatus species-group.

Highlights

Moenkhausia Eigenmann, 1903 is one of the most species-rich genus in Characidae with 93 valid species (Soares, Benine, 2019; Soares et al, 2019), behind only of Hyphessobrycon Durbin in Eigenmann, 1908 (158 spp.) and Astyanax Baird, Girard, 1854 (126 spp.) (Fricke et al, 2020; Terán et al, 2020), and widely distributed in the cis-Andean basins of South America
We have examined only two lots of M. melogramma from Ecuador in the present study, a cursory examination of the material identified as Hemigrammus lunatus from both the Napo and Putumayo basins in Ecuador, deposited at FMNH and MEPN, by one of the authors (FCTL), showed it to belong mostly to M. melogramma
Eigenmann (1908) mentioned that the color pattern of Moenkhausia melogramma consisted in the presence of a line along the anal-fin base, a faint longitudinal midlateral dark stripe, and absence of blotches

Summary

Introduction

Moenkhausia Eigenmann, 1903 is one of the most species-rich genus in Characidae with 93 valid species (Soares, Benine, 2019; Soares et al, 2019), behind only of Hyphessobrycon Durbin in Eigenmann, 1908 (158 spp.) and Astyanax Baird, Girard, 1854 (126 spp.) (Fricke et al, 2020; Terán et al, 2020), and widely distributed in the cis-Andean basins of South America. The genus remains diagnosed by a combination of characters that includes two series of teeth on premaxilla, five teeth in the inner tooth series of the premaxilla, a complete lateral line, and caudal fin partly covered by small scales (Eigenmann, 1917). The lateral line completeness has been confirmed as a highly homoplastic character (Mirande, 2010, 2019), a suspected condition that has prompted some authors to assign species having incompletely pored lateral line in Moenkhausia (i.e., M. pyrophthalma Costa, 1994; M. diktyota Lima, Toledo-Piza, 2001; M. cosmops Lima, Britski, Machado, 2007; M. forestii Benine, Mariguela, Oliveira, 2009, and M. uirapuru Ohara, Lima, 2015). Moenkhausia melogrammus was described by Eigenmann (1908) based on a single specimen from upper Amazon basin in Tabatinga, Amazonas State, Brazil (MCZ 20825), which was collected during the Thayer Expedition and was only described 43 years later (Fig. 1). The original description only mentioned the number of fin rays, the misalignment of the third premaxillary tooth of the outer row in relation to the other teeth, and general color pattern, characterized by the absence of blotches, presence of a faint stripe along mid-body, and presence of a dark stripe along the anal-fin base

Methods

Results

Conclusion