Revisão taxonômica de astyanax eigenmanniorum (cope, 1894) com base em caracteres morfológicos (ostariophysi : characiformes : characidae)

Abstract

Taxonomic review of Astyanax eigenmanniorum (Cope, 1894) based in morphological characters (Ostariophysi: Characiformes: Characidae) Astyanax eigenmanniorum (Cope, 1894) was originally described from Rio Grande do Sul State without a precise type locality. Later, the species was restricted to the Laguna dos Patos system, however no further study on the diagnosis was published since the original description. The aim of this study was to analyze the variation between different populations of Astyanax eigenmanniorum considering its geographical distribution, based on f morphological characters through morphometric and meristic analyses and color pattern of individuals seeking to detect possible distinct lineages. For this purpose, three areas in southern Brazil and Uruguay were selected, because of its endemism level of fish fauna. They are: Tramandaí river system (A1), Laguna dos Patos system (A2), and middle/lower Uruguay river system (A3). Morphometric analyses comprised the traditional measurements and counts, and geometric morphometry. The analyses included 705 specimens examined, deposited in the fish collections of the Museu de Ciências e Tecnologia da Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre (MCP), Museu de Ciências Naturais, Porto Alegre (MCN), Universidad de la Republica, Montevideo (ZVCP), Universidade Estadual de Maringá, Maringá (UEM), Universidade Estadual Paulista, São José do Rio Preto (UNESP), Universidade Federal do Rio Grande do Sul, Porto Alegre (UFRGS) e Universidade São Paulo, Ribeirão Preto, (LIRP). Nineteen measurements of body and head were taken using digital calliper, 14 counts under a stereomicroscope with incident light and 40 cleared and stained individuals were used for the 18 counts, particularly those regarding the number of teeth and cusps, vertebrae and supraneurals. For the geometric morphometry analysis, the specimens were photographed and 11 homologous points on the body were defined to verify possible variations in centroid size and shape. The populations were firstly examined separately considering the presence or absence of hooks on the anal and ventral fins, and the 2nd humeral spot. By confirming the uniformity of results within each area, the data and analyses were conducted between the different areas. Measurement and counts were analyzed with DATAX for Windows software version 1.01, and PAST program (Paleontological Statistics, version 3.12) was used for Principal Components Analysis and the Discriminant Function, aiming to graphically represent the groups formed. The geometric morphometry analyses and graphs were performed in MorphoJ version 1.06 and R version 3.6.1. The results showed some morphological variation between the areas more distant geographically, but without sufficient support to confirm them as a distinct species. The variation range of meristic and morphometric data, and color pattern for the species in relation to what is currently known is expanded. As a result, Astyanax eigenmanniorum is herein redescribed. It is noticeable, by the results achieved, the capacity of adaptation of A. eigenmanniorum to different environments, as well as its phenotypic plasticity.