Confirmation of sexual dimorphism in Hoplias aimara (Valenciennes, 1847) (Erythrinidae: Characiformes) proposed by local expertise in Amapá, Brazil

Abstract

Fishes may show sexual dimorphism according to their reproductive strategies. In some species, this differentiation is already well known. However, with the findings obtained from recent studies, the number of species for which sex can be determined without dissection has increased. Thus far, the presence of external secondary sexual characteristics in Hoplias aimara, a very well-studied species, has not been reported. Traditional knowledge evidenced through riparian people observations indicated the possibility of sexual dimorphism in this species, which was studied in 2 conservation units, Sustainable Development Reserve of Iratapuru River and Tumucumaque Mountains National Park, in the state of Amapá, Brazil. Fishes were captured, and their anal fins were examined when they were still fresh; the sex of the fishes was confirmed by dissection. The same procedure was used for formalin-fixed fishes. By assessing the shape of the anal fin in fresh or fixed fishes, it was possible to determine the sex of the fish, which was then confirmed by dissection. H. aimara shows sexual dimorphism expressed in the morphology of their anal fin. Thus, the sex of fishes deposited in collections can be identified without any dissection, thereby providing important biological information about the specimens.Keywords: local knowledge, ethnoichthyology, Tumucumaque, Iratapuru. Confirmação do dimorfismo sexual em Hoplias aimara (Valenciennes, 1847) (Erythrinidae: Characiformes) proposto por ribeirinhos no Amapá, Brasil ResumoOs peixes podem exibir dimorfismo sexual conforme suas estratégias reprodutivas. Em algumas espécies essa diferenciação já é bem conhecida, no entanto, novos estudos têm aumentado o número de espécies que não precisam de dissecção dos indivíduos para o reconhecimento do seu sexo. A espécie Hoplias aimara, apesar de muito bem estudada ainda não apresentava registro da presença de caracteres sexuais secundários externos. O conhecimento tradicional de ribeirinhos indicou a possibilidade da existência de dimorfismo sexual para esta espécie que foi estudada em duas unidades de conservação no Estado do Amapá, a Reserva de Desenvolvimento Sustentável do rio Iratapuru e o Parque Nacional Montanhas do Tumucumaque. Os indivíduos capturados, ainda frescos, tiveram sua nadadeira anal examinada e seu sexo confirmado através de sua dissecção. Indivíduos fixados também passaram pelo mesmo procedimento. Através do formato da nadadeira anal, seja em indivíduos frescos ou fixados, foi possível inferir o sexo de cada indivíduo, que foi confirmado através de sua dissecção. A espécie Hoplias aimara apresenta dimorfismo sexual manifestado na morfologia de sua nadadeira anal. Indivíduos depositados em coleções podem ter seu sexo observado sem sua dissecção, acrescentado informações importantes à biologia dos espécimes.Palavras-chave: conhecimento local, etnoictiologia, Tumucumaque, Iratapuru.

Current situation and future perspectives of ethnoichthyology in Brazil

“…Studies on morphological aspects have aided researchers in identifying signs of sexual dimorphism in species in which sex cannot be precisely determined. For example, this approach have been used to Pirarucu Arapaima gigas Schinz, 1822 in the Amazon (Lopes and Queiroz 2009) and for Hoplias aimara Valenciennes, 1847, as noted by Gama (2014) in his study carried out in the state of Amapá, which reported evidence of external sexual characteristics in this species for the first time based on the personal observations of local fishermen during scientific expeditions in the region.…”

New remarkable sexually dimorphic miniature species of Hyphessobrycon (Characiformes: Characidae) from the upper Rio Tapajós basin

“…According to Rapp Py‐Daniel & Fernandes (), fishes are particularly interesting and informative organisms in studies of sexual dimorphism due to many specializations found between the sexes. Characiformes is one of the largest components of the freshwater fish fauna world‐wide, spanning numerous examples of sexual dimorphism (Weitzman & Cobb, ; Vari, ; Weitzman & Palmer, ; Zanata & Vari, ; Menezes & Weitzman, ; Gama, ; Malabarba & Jerep, ; Zanata & Camelier, ; Ota et al, ). Such cases are particularly profuse in Characidae, the most diverse family of the order (Mirande, ; Oliveira et al, ).…”