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.
Highlights
The evolution of secondary sexual characteristics is usually the result of a disparity in the parental investment of males and females (Trivers, 1972; Andersson, 1994)
The fishes analysed were collected during expeditions to Sustainable Development Reserve of Iratapuru River and Montanhas do Tumucumaque National Park, which were state and federal conservation units, respectively
We observed the shape of the anal fins of all the captured fishes, which were dissected for sex confirmation
Summary
The evolution of secondary sexual characteristics is usually the result of a disparity in the parental investment of males and females (Trivers, 1972; Andersson, 1994). In some cases, this disparity can be exclusively attributed to size differences between males and females. Many teleost fishes do not exhibit any sexual dimorphism, even during the spawning season, and do not show sexual characteristics or permanent ornaments. Some fishes show permanently dimorphic traits that are not necessarily associated with internal fertilization Biol., 2014, vol 74, no. 3, p. 687-690
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