Esteróides gonadais e metabolismo lipídico ao longo do ciclo reprodutivo de Arapaima gigas (SCHINZ, 1822) em ambiente natural / Gonad steroids and lipid metabolism along the reproductive cycle of Arapaima gigas (SCHINZ, 1822) in natural environmet

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The aim of the present study was to investigate the possible physiological alterations related with reproduction in males and females of Arapaima gigas (pirarucu) in their natural environment. Pirarucu is an obligatory aerial respiration species belonging to a very ancient group of teleosts and inhabits Amazonian river. The main goals of this study were to describe the plasmatic gonad steroids profile (17β-Estradiol, Testosterone, 11keto-Testosterone (11keto-T) and 17α- hidroxyprogesterone (17α-OHP)), lipids and proteins concentrations of the main storage tissues (gonads, white muscle, red muscle and ventrecha), and fatty acid profile along the reproductive cycle of males and females collected in their natural environment at Ilha Mexiana (Pará/ Brazil). The animals were caught from the wild in September/2007, January/2008, July/2008 and September/2008 and four stages of gonad development were determined: Rest, Maturation, Mature and Regression. Immature animals were also observed. Males were classified according to spermatozoid amount inside the seminiferous tubes, and the animals having a few spermatozoids were referred as group1 and those having many spermatozoids were referred as group 2. Microscopic analyses allowed concluding that pirarucu has gymno-ovary type with assynchronic oocyte development and testis has non-cystic structure. The metabolic analyses in females showed that the tissue presenting the highest lipids concentration was the ventrecha, followed by the red and white muscle, suggesting that ventrecha is the preferred lipids storage among different muscles. Lipids concentrations increased in ovaries and liver along the reproductive cycle, getting the highest value at mature stage. Liver and gonads protein did not show any difference among the reproductive stages. Lipids and proteins in males did not present any difference between the groups of any analyzed tissue. In polar lipids ovary fraction, PUFA (polyunsaturated fatty acids) n3 were higher at mature stage, compared with the other stages of the reproductive cycle and immature animals, and these high amounts reflect the importance of those fatty acids, that will be used in the larval development. In general, the immature animals showed the highest percentage of PUFA n6 (polar fraction) and PUFA n3 (neutral fraction) in the liver when compared with adults females. Monounsaturated fatty acids in males in group 2 were higher in white muscle and ventrecha, because those muscles have an intense energetic demand for reproductive behavior. 17β-Estradiol was higher in females, at initial stages of the reproductive cycle, decreasing at mature and regression stages, probably due to a negative feedback. Immature animals showed the highest concentrations of 17β-Estradiol and 17α-OHP, probably because these steroids stimulate sexual secondary features, neural development, growth and sexual maturity in those animals. 17α-OHP concentrations were higher in both male groups, suggesting its availability for 17α, 20β-DHP conversion, an important steroid on spermatozoid motility. Testosterone concentrations in males exceed 11ceto-T, suggesting that other androgens were more effective and not just 11ceto-T, for reproduction. On this environment, features like scales coloration as secondary feature were not suggested to distinguish the sex of those animals, but it is possible when using 11ceto-T and 17β- Estradiol plasma ratio.

ASSUNTO(S)

esteróides gonadais controle endócrino reprodutivo fish arapaima gigas gonad steroids reproduction lipid metabolism fatty acids metabolismo lipídico reprodutivo

ACESSO AO ARTIGO

Documentos Relacionados