Revisão taxonômica da espécie Hoplias malabaricus (Characiformes: Erythrinidae) presentes na Restinga de Jurubatiba (Rio de Janeiro: Norte Fluminense)

Abstract

Teleost fishes of the order Characiformes, widely distributed in Africa and in Central and South America, form one of the largest and most diverse assemblages of freshwater fishes. In Central and South America, the family Erythrinidae includes the genera Erythrinus (Scopoli, 1777), Hoplerythrinus (Gill, 1896), and Hoplias (Gill, 1903). Among the species of this family, Hoplias malabaricus (Bloch, 1794) represents one of the greatest taxonomic challenges of the Neotropical ichthyofauna due to the complexity of its identification and the morphological variations it presents, currently being recognized as a taxonomic complex. Located on the northern coast of the state of Rio de Janeiro, the Restinga de Jurubatiba National Park comprises eighteen coastal lagoons with a wide variation in their environmental characteristics. These lagoons differ both in their geographic orientation, aligned either parallel or perpendicular to the coastline, and in salinity levels, ranging from freshwater to hypersaline conditions. In the present study, six of these lagoons were selected for the collection of Hoplias malabaricus specimens, with the aim of conducting anatomical and molecular analyses. Additionally, the variation in salinity parameters was investigated specifically in those lagoons where the specimens were found, in order to better understand the environmental conditions associated with the occurrence of the species. The anatomical analyses were compared with material from various hydrographic basins in South and Central America, as well as with data from the literature. For the molecular analyses, comparisons were made with information available in the BOLD and GENBANK databases. The results showed significant anatomical variations as well as considerable molecular divergences in relation to other species of the H. malabaricus complex. Among the exclusive anatomical characters, the following stand out: keyhole-shaped mandibular symphysis; lateral ethmoid with a sharp process projected ventrolaterally; large jugular depression on the lateral surface of the cranial box; and a circumorbital series in which the infraorbital bone 5 does not have pores for the sensory canal, and the infraorbital 6 has a rectangular shape. Other features include pectoral fins with 12–13 segmented and branched rays, dorsal fin with 14 rays, pelvic fin with 9 segmented and branched rays, and a caudal fin with 17 rays (10 in the upper lobe and 7 in the lower lobe). Genetic divergence between Hoplias malabaricus groups was approximately 7.7% compared to the Rio Doce (MG) group and about 8.3% compared to H. malabaricus sensu stricto from northern and northeastern Brazil. Although H. malabaricus is traditionally recognized as a freshwater species with low tolerance to salinity, the specimens analyzed were recorded in lagoons with a wide salinity range, from brackish environments, such as Lagoa do Paulista (3 ‰) and Lagoa de Carapebus (4 ‰), to hypersaline environments, such as Lagoa da Garça (47 ‰) and Lagoa do Visgueiro (45 ‰). The combined use of anatomical and molecular techniques proved to be fundamental for the study of this population present in the lagoons of the Restinga de Jurubatiba National Park, contributing not only to the resolution of taxonomic questions within the genus Hoplias, but also to the understanding of the evolutionary and biogeographic processes that have influenced the species in the region.