IBBEA   24401
INSTITUTO DE BIODIVERSIDAD Y BIOLOGIA EXPERIMENTAL Y APLICADA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Brain in the endangered neotropical catfish species Steindachneridion parahybae (Siluriformes: Pimelodidae): main nucleus related to reproduction during ontogeny
Autor/es:
MEDRADO, A. T.; MOREIRA, R. G.; CANEPPELE, D.; HONJI, R. M.
Lugar:
Olhão
Reunión:
Simposio; 10th International Symposium on Reproductive Physiology of Fish; 2014
Resumen:
Introduction The studies on reproductive endocrinology in fish have contributed to understanding the main factors that can influence the entire reproductive process either in both, captive and/or in wild environments. However, baseline studies enabling the basic morphological knowledge of the species are required for further investigations. In this sense, the present work aims to present a cytoarchitectonic study in the brain of the endangered Neotropical catfish species, Steindachneridion parahybae, describing the main nuclei related to the reproductive process. Methods Fertilized eggs of S. parahybae were obtained from artificially induced spawning at CESP (Companhia Energética do Estado de São Paulo) fish farm, and transferred to aquaria in a biotherium at USP (Universidade de São Paulo). During the first ten days after hatching (DAH), five animals were sampled; thereafter, five animals were sampled every three DAH, until the one hundreth DAH. The animals were anaesthetized with benzocaine and then fixed in Bouin?s solution for 20 hours. Samples were dehydrated and embedded in Paraplast®. For the analyses of the main encephalic nucleus, serial transverse sections (10!m) were stained with cresyl-violet. Different cell groups were identified, following some criteria: density of cell bodies, staining intensity and pattern of distribution of cell bodies. For the analyses of the slices and documentation of the images, a computer system was used. The identification of the main nuclei was made based on studies related to the identification and localization of the GnRH (gonadotropin-releasing hormone) neurons in catfish. Results and Discussion The main encephalic nuclei in S. parahybae, which are directly related to reproduction, can be easily distinguished on the 40th DAH. These nuclei were predominant in: forebrain (telencephalon, olfactory bulbs, and diencephalon) and mesencephalon (midbrain tegument). The telencephalic nuclei were divided into dorsal and ventral, which may be still subdivided in: dorsal, ventral, lateral and central part of the dorsal and ventral telencephalon. The diencephalic nucleus was mainly divided into: gigantocellular part of the magnocellular preoptic nucleus (PMgc), anterior periventricular nucleus (NAPv), suprachiasmatic nucleus (NSC) and ventromedial thalamic nucleus (VM) (which are located in the periventricular region); and the inferior lobe of the hypothalamus (IL). Previous studies in S. parahybae, as well as in Clarias gariepinus, showed the presence of GnRH neurons in this region, which were identified in the midbrain tegument, preoptic area and in areas of the hypothalamus and inferior lobe of the hypothalamus. These last two regions are reported as the main regions related to reproduction in teleosts. The development of the pituitary occurred on the 40th DAH. Additionally, S. parahybae showed a well developed cerebellum compared to other teleosts, and a long medium olfactory tract. Conclusion The cytoarchitectonic pattern in S. parahybae is similar to that observed in other teleosts, except for a larger cerebellum and a longer medium olfactory tract, compared to some teleosts. Thus, this study is most important to understand the basic physiology of this endangered species.