Abstract
Teleostei present great plasticity regarding sex change. During sex reversal, the whole gonad including the germinal epithelium undergoes significant changes, remodeling, and neoformation. However, there is no information on the changes that occur within the interstitial compartment. Considering the lack of information, especially on the role played by metalloproteinases (MMPs) in fish gonadal remodeling, the aim of this study was to evaluate the action of MMPs on gonads of sex reversed females of Synbranchus marmoratus, a fresh water protogynic diandric fish. Gonads were processed for light microscopy and blood samples were used for the determination of plasma sex steroid levels. During sex reversal, degeneration of the ovaries occurred and were gradually replaced by the germinal tissue of the male. The action of the MMPs induces significant changes in the interstitial compartment, allowing the reorganization of germinal epithelium. Leydig cells also showed an important role in female to male reversion. The gonadal transition coincides with changes in circulating sex steroid levels throughout sex reversion. The action of the MMPs, in the gonadal remodeling, especially on the basement membrane, is essential for the establishment of a new functional germinal epithelium.
Highlights
Sex change, one of the most controversial and remarkable expressions of plasticity in sexual development, can be observed in a number of teleost orders and families
The extracellular matrix components of the interstitial tissue of the gonads of the Synbranchus marmoratus are remodeled through the metalloproteinases (MMPs) according to morphophysiological alterations that occur during sex reversal
The breakdown of the basement membrane is the trigger to initiate the remodeling in both compartments and this is due to the action of matrix metalloproteinases (MMPs), produced by different cell types
Summary
One of the most controversial and remarkable expressions of plasticity in sexual development, can be observed in a number of teleost orders and families. A species or population is considered to exhibit functional hermaphroditism if a proportion of individuals function as both sexes at some time in an individual’s life history. This natural sex reversal process basically consists of the expression of both male and female reproductive functions in a single individual; the proliferation of secondary-sex gonadal tissue and the simultaneous degeneration of the primary-sex gonadal tissue [1,2,3,4]. In cases of protogynous hermaphroditism, most frequently observed in teleosts, individuals first develop into females and later, have their functional ovaries gradually replaced by male tissue. A decrease in female gametogenesis and an increase in the male tissue activity are observed during sex reversal; protogynous species may show monandry, in which all males are secondary males arising from the sex reversed females, or diandry, in which there are two types of males: those that develop as primary males and those that are secondary males [1,5,6]
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