Morphological characterization of the GnRH system and pituitary gland in the Neon Cardinal Parancheirodon axelrodi

LAURA RINCÓN CAMACHO; ANDREA POZZI; MATIAS PANDOLFI

Manaus

Simposio; 11th International Symposium on Reproductive Physiology of Fish; 2018

IntroductionParancheirodon axelrodi (Characiforms, Characidae) is a Neotropical fish distributed in Black and Orinoco rivers of South America. In many countries, P. axelrodi is widely commercialized as an ornamental species (ie: 34% of imports in Argentine), although there are no successful studies or standardized protocols for its culture. Considering that it is an overexploited species from Amazonian rivers, it is important to deepen the knowledge regarding its reproductive physiology from different approaches. The purpose of this study was to perform the first morphological characterization of the GnRH neuronal system and pituitary gland in this species.MethodsAdult male and female heads were fixed in a Bouin?s solution, dehydrated and embedded in paraplast. For histochemical studies of the pituitary, sagittal and transverse sections were stained with periodic acid-Schiff (PAS) and Masson trichrome. For immunohistochemical analysis, brain, pituitary and gonadal sections were immunostained according to SABC complex (streptavidin-biotin-peroxidase complex) with several heterologous antisera which specificity was corroborated by Western blot and preabsortion tests in several species. Results and Discussion Three principal populations of GnRH cell bodies were detected by IHQ: GnRH I (ir-salmon GnRH) in the anterior preoptic area, GnRH II (ir-chicken II GnRH) in the midbrain tegmentum and GnRH III (ir-salmon GnRH) in the caudal olfactory bulbs. Regarding the pituitary gland, in the rostral pars distalis ir-ACTH and ir-PRL cells were found forming compact clusters. Fusiform ir-βFSH cells were also found. Within the proximal pars distalis, ir-GH cells, and round ir-βFSH and ir-βLH cells were abundant in its dorsoventral portion. We were not able to detect ir-TSH cells with the antisera used. In the pars intermedia, ir-MSH and ir-SL cells were found surrounding the neurohypophyseal branches. Ir-salmon GnRH fibers reached the pituitary gland. Finally, ir-PRL, βFSH and βLH cells were detected in previtelogenic oocytes. Conclusion This is the first morphological study of the brain GnRH system and pituitary components of the Cardenal Neon, P. axelrodi. The results showed the presence of three populations of GnRH cells, and a distribution pattern of pituitary cells similar to other teleost species, only with slight differences in βFSH distribution.