ABSTRACT
During the fish reproductive cycle, testes undergo morphological changes related to germinal epithelium and remodeling of extracellular matrix components (ECM). ECM is degraded mainly by action of matrix metalloproteinases (MMPs). Due to the natural renewal of ECM in fish testes, we choose Pimelodus maculatus to study remodeling of ECM throughout reproductive cycle, using picrosirius (to identify type I, II, III collagen) and reticulin (type III collagen), and to immunolocalize MT1-MMP (membrane type 1-matrix metalloproteinase) and MMP-2 in testis cells. Testes were classified in four reproductive phases: regenerating, development, spawning capable and regressing. Picrosirius and reticulin demonstrated a differential distribution of total collagen fibers during the reproductive cycle. Immunohistochemistry showed MT1-MMP only in acidophilic granulocyte cells mainly inside blood vessels, in connective tissue of capsule close to the germinal compartment, and also infiltrated in interstitial connective tissue. MMP-2 was detected in fibroblast and endothelial cells of interstitial and capsule blood vessels, in epithelial cells of capsule, and in acidophilic granulocyte cells at same description for MT1-MMP. The fish testes ECM were remodeled throughout reproductive cycle in according to morphophysiological alterations. During reproductive season (spawning capable), the interstitium increased in total collagen fibers (type I, II, III). After spermiation period (regression and regenerating), the amount of collagen fibers decreased in response to action of MMPs on collagen degradation and other interstitial components (not assessed in this study). MMPs seem to be indispensable components for natural cyclic events of ECM remodeling of fish testes and for guarantee tissue homeostasis throughout reproductive cycle.
Subject(s)
Catfishes/physiology , Extracellular Matrix/physiology , Reproduction/physiology , Testis/physiology , Animals , Gene Expression Regulation/physiology , Male , Matrix Metalloproteinase 14/genetics , Matrix Metalloproteinase 14/metabolism , Matrix Metalloproteinase 2/genetics , Matrix Metalloproteinase 2/metabolism , SeasonsABSTRACT
This study evaluated the diet and reproductive aspects of the population of Pimelodus maculatus around net cage fish farming in order to assess the possible impacts of this activity. Monthly collections were performed from March 2008 to February 2009 on two populations: one close to the net cages (NC) and one from an area not influenced by these cages denominated the "reference site" (RS). Results of the Alimentary Index (AI), Gonadosomatic Index (GSI), reproductive potential and histological analysis were obtained for both NC and RS populations. The population from NC used leftover food (ration) that escapes from net cages as the main food item (99.3%). For the RS population, the detritus item was the more important food source (51.7%). The Detrended Correspondence Analysis (DCA) showed that the use of food resources was different between the two sites. The reproductive period of the species (indicated by the GSI) revealed that the population of the NC showed an extended reproductive period compared to RS. The histology of the ovaries indicated that the specimens in the NC were spawning capable. This study indicates that fish farming activities influence the species P. maculatus in the Chavantes reservoir by adding a new resource to the food web.
O objetivo deste estudo foi avaliar a dieta e os aspectos reprodutivos da população de Pimelodus maculatus residentes ao redor de tanques-rede. Os peixes foram coletados mensalmente, de março/2008 a fevereiro/2009, a partir de duas populações: uma próxima ao ambiente de tanques-rede (NC) e a outra em uma área não influenciada pelos tanques-rede, denominada área de referência (RS). As análises do Índice Alimentar (AI), Índice Gonadossomático (IG), Potencial Reprodutivo e Histologia das gônadas foram realizadas para as populações das duas áreas amostradas. As populações de NC utilizaram-se de restos de ração que escapam dos tanques-rede, como principal fonte alimentar (99,3%). Para a população do RS, os detritos foram a fonte mais importante (51,7%). A análise de Correspondência Destendenciada (DCA) mostrou diferenças na utilização dos recursos alimentares entre as duas populações. O período reprodutivo das espécies (indicado pelo IG) mostrou que a população do NC apresentou maior período reprodutivo em relação às populações do RS. A histologia dos ovários indicou que os espécimes de NC estavam aptos à desova. Este estudo adverte que as atividades de piscicultura influenciam a referida espécie na represa de Chavantes pela adição de um novo recurso para a cadeia alimentar.
