Warm water induces apoptosis, gonadal degeneration, and germ cell loss in subadult pejerrey Odontesthes bonariensis (Pisces, Atheriniformes).

Abstract Recent studies have shown that exposure to warm water can trigger gonadal degeneration and germ cell loss in fish of both sexes, but the mechanism behind this pathology is still not understood. This study was designed to characterize this process histologically and determine whether apoptosis plays any role during high temperature-induced gonadal cell degeneration in subadult pejerrey (Odontesthes bonariensis). For this purpose, fish were reared continuously at constant temperatures of 24 degrees C (control) and 29 degrees C (prolonged heat stress) or exposed for 36 h to 31 degrees C and then returned to 24 degrees C (short heat stress).

Thermal threshold and histological process of heat-induced sterility in adult pejerrey (Odontesthes bonariensis): a comparative analysis of laboratory and wild specimens.

Elevated water temperature has been found to cause gonadal degeneration in fish, including the partial or complete loss of germinal elements, and might impair fertility and reproductive performance. Germ cell-deficient and even completely sterile pejerrey Odontesthes bonariensis have been found in two lagoons in Argentina, and exposure to warm water is one of the possible causes of these abnormalities. This experiment was conducted (a) to compare the histological characteristics of the abnormal gonads from wild pejerrey with those of animals exposed to heat in the laboratory and (b) to examine whether short-term pulses of heat similar to diurnal temperature variations in natural environments during summer can trigger gonadal cell degeneration in adult pejerrey.

Where does gonadal sex differentiation begin? Gradient of histological sex differentiation in the gonads of pejerrey, Odontesthes bonariensis (Pisces, Atherinidae).

This study investigated the possibility that the histological process of gonadal sex differentiation in pejerrey (Odontesthes bonariensis), a fish with marked temperature-dependent sex determination (TSD), occurs through a predictable gradient of differentiation as opposed to simultaneous or random differentiation throughout the gonad. For this purpose, fish reared at 17 degrees, 24 degrees, and 29 degrees C from hatching were sampled weekly for 11 weeks, fixed, and prepared for histological observation of serial cross-sections of the gonads. The thermal manipulation and sampling procedure ensured the availability of males and females at various degrees of gonadal sex differentiation.

Dynamics and histological characteristics of gonadal sex differentiation in pejerrey (Odontesthes bonariensis) at feminizing and masculinizing temperatures.

This study evaluated the effects of different temperatures on the histological process of sex differentiation in the pejerrey Odontesthes bonariensis, a fish with marked temperature-dependent sex determination (TSD), at feminizing, neutral, and masculinizing temperatures. Fish reared at three temperatures (17 degrees C, 24 degrees C, and 29 degrees C) from hatching were sampled weekly until 11 weeks and their gonads were examined by histology. The percentages of females at 17 degrees C, 24 degrees C, and 29 degrees C were 100%, 73%, and 0%, respectively.

Histological process and dynamics of germ cell degeneration in pejerrey Odontesthes bonariensis larvae and juveniles during exposure to warm water.

Elevated temperature causes degeneration and disappearance of the germ cells in the males of scrotal mammals. It was recently shown that heat-induced germ cell degeneration occurs also in fish but, unlike in mammals, it occurs not only in males but also in females. The purpose of this study was to clarify the histological process and dynamics of heat-induced germ cell disappearance in pejerrey Odontesthes bonariensis larvae and juveniles.