Biologia reprodutiva, expressão de IGF1 e IGF2, proliferação e morte celular durante a maturação testicular do cascudo Hypostomus garmani no alto Rio das Velhas

Abstract

The reproduction of many teleost fish species is an annual cyclic event where thousands to millions of gametes are produced. During the reproductive cycle, fish ovaries and testes undergo intense remodeling to support the production of gametes, being the gonadal morphological dynamics guided by the action of several endocrine, paracrine and autocrine factors. Among these, the influence of insulin-like growth factors (IGFs) on the proliferation and cell death dynamics during gametogenesis is poorly investigated. Studies about reproductive biology and molecular events cascade that occur during gametogenesis and gonadal maturation of fish provide important data, which can be applied to commercial breeding and biodiversity conservation. The present work had the goal of analyzing the reproductive biology, spermatogenesis and testicular maturation of Hypostomus garmani (Siluriformes: Loricariidae) in upper Rio das Velhas, using histology, carbohydrate histochemistry, morphometry and immunohistochemistry. The results demonstrated that the spawning period of H. garmani is concentrated from december to march, with partitioned spawning. The vitellogenic follicles presented large diameter, thick zona radiata, columnar follicular cells and the presence of neutral glycoprotein and mucopolysacharides in their enveloping layers. In the testis, IGF1 expression predominated in the stages of resting and maturation while both, IGF1 and IGF2, occurred in the mature and spawned stages. These results indicate that germ cell proliferation (Ki67-positive cells) was influenced mainly by the action of IGF1 in the early stages of testicular maturation while testicular remodeling was influenced by the combined action of IGF1 and IGF2. Apoptosis (TUNEL-positive cells) was more frequent in spermatocytes and spermatids when IGF1 and IGF2 expression was reduced. Our results suggest that H. garmani spawns in environments subject to abrasion, has adhesiveness eggs, exhibits parental care behavior and the expression of IGF1 and IGF2 modulates the dynamics of proliferation and cell death throughout testicular maturation.