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Made available in DSpace on 2022-04-29T08:31:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Fish are affected by environmental variables that influence their survival and reproduction, showing physiological responses in an attempt to maintain internal homeostasis. Several Poeciliidae, native from brackish water body regions, can be acclimated to live in saltwater. The introduction of Xiphophorus maculatus in saline environments is possible, although it is not a brackish water species. Thus, to evaluate the effects of the salinity variation on the acclimatization of X. maculatus, the specimens were exposed to different salinities (from 15 to 30 ppt) for up to 40 days, acutely and gradually. After exposing, their gonads, gills, cortisol and glucose levels were analysed. When transferred to salt or brackish water, cortisol and glucose levels increased, peaking at 30 min. Immunohistochemistry showed increased expression of Na+/K+-ATPases in the mitochondria-rich cells (MRCs) of the gill, as salinity increased. The female and male germinal epithelium remained unchanged. Xiphophorus maculatus was able to acclimatize and reproduce in saltwater, and their offspring survived in this environment, when there was gradual acclimatization of the adults to different salinities. However, in an abrupt exposure, the salinity became a stressor agent and could cause its mortality. Department of Cell and Developmental Biology Institute of Biomedical Sciences Federal University of Alfenas (UNIFAL-MG) Department of Morphology Botucatu Biosciences Institute State University of São Paulo (UNESP) Department of Morphology Botucatu Biosciences Institute State University of São Paulo (UNESP)

Telocytes are a new defined type of interstitial cells, considered as a stem cell, with very long and thin cytoplasmic extensions. They are present in the vertebrates, and may participate in tissue remodeling. In fish, during gonadal development, the events that culminate with the germinal epithelium formation are well known. However, the interstitial compartment remains poorly explored, although it may have a great contribution to the morpho-functional changes that occur in the gonad. As in other organisms, in fish, the interstitium consists especially of connective tissue elements. However, until now, there are no reports of the presence and the action of the telocytes in the connective tissue of gonads of fish. Thus, this study aimed to detect the presence, localization and morphology of telocytes during the gonadal development of several species of fish. The gonads were analyzed by light microscopy, transmission electron microscopy and immunohistochemistry for localization of CD34, Vimentin, and metalloproteinases. The presence of two proteins characteristics of mesenchymal cell was detected in cells of the gonads of all species. In addition, they presented a typical morphology of telocytes, showing cellular extensions. Gonadal telocytes also presented positive response to metalloproteinases. In mammals, telocytes can undergo de-differentiation contributing to the reorganization of the extracellular matrix. This role may be performed by the metalloproteinases detected here. The detection of Vimentin and CD34 in the same cellular type, associated with its morphological characteristics, allows us to conclude that some interstitial cells in Teleostei are considered telocytes, identical to the ones already described in mammals and other vertebrates.