Caráter sexual secundário em Brycon orbignyanus (Characiformes: Bryconidae) e sua associação com o período reprodutivo

• Autor(a) principal: Bianchini, Bárbara Correa
• Data de Publicação: 2022
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/216444
• topic: Sexual dimorphism; Reproduction of fish; Spicules piracanjuba; Dimorfismo sexual; Espículas; Piracanjuba; Reprodução de peixes; Piracanjuba

Secondary sexual characteristics are differences between males and females, not related to reproductive organs, but morphological differences such as color, size or accessory structures associated with reproduction. In Brycon orbignyanus males can be distinguished from females by means of a roughness felt in the anal fins, which appear in the reproductive period and are called spicules. Although present in the reproductive period of the species, little is known about the synergy between testicular development and the appearance of spicules. Thus, the objective of this work was to analyze the secondary sexual characteristics in males of B. orbignyanus relating them to the phase of the testicular cycle, aiming at the identification of this characteristic for the selection of breeding males in captivity. To this end, 20 specimens of B. orbignyanus were collected at the ages of one to three years from the Experimentation greenhouse of the Neotropical Ichthyology Laboratory – LINEO (UNESP-FEIS), conditioned in water recirculation systems (4,500 L at 27 ± 0 .5°C). The specimens were euthanized in benzocaine solution and had the anal fin and testes removed. Anal fins were dehydrated in ethanol and processed for scanning electron microscopy. The testes were sectioned, fixed in 2% glutaraldehyde, 4% paraformaldehyde and Sorensen phosphate buffer - pH 7.2, embedded in glycolmethacrylate and processed for light microscopy. Both ages had 22-28 rays per anal fin. The fins had reddish and black coloration, with larger rays in the cranial region, decreasing as they approach the caudal region. The rays are bifurcated and segmented, so that the spicules are more concentrated in the cranial portion of the fin, being found from the second to the sixteenth ray, only one per segment. Microscopically, they are keel-shaped projections, with broad bases and hook-shaped terminal portions. Animals were found in two distinct phases: Immature and Able to Sperm, so that the appearance of spicules is associated with testicular development, being absent in Immature specimens and present in animals in the Apt to Sperm phase. In this phase, there is an increase in the number of rays with spicules with the advancement of spermatogenesis. Thus, the spicule is a secondary sexual characteristic to be used for the selection of breeding males in captivity.