High Water Temperatures Impair the Reproductive Ability of the Pejerrey Fish Odontesthes bonariensis: Effects on the Hypophyseal-Gonadal Axis.

SORIA FN; STRUSSMANN CA; MIRANDA LA

PHYSIOLOGICAL AND BIOCHEMICAL ZOOLOGY

University of Chicago Press

Lugar: Chicago 81(6):898–905.; Año: 2008 vol. 81 p. 898 - 905

1522-2152

The aim of this research was to study how high water temperatures impair the reproductive activity of pejerrey Odontesthes bonariensis, an inland-water atherinopsid fish species from the pampasic region of Argentina. Adult pejerrey of both sexes were kept under a control-temperature regime (19C) and two experimental temperatures (23 and 27C) for 8 d. The effect of elevated temperature on the pituitary-gonad axis was analyzed in terms of the expression of gonadotropin (GtH) subunits: follicle-stimulating hormone b, luteinizing hormone b (LH-b), glycoprotein hormone a, and GtH receptors FSH-R and LH-R by semiquantitative reverse transcriptase polymerase chain reaction, plasma levels of sexual steroids by radioimmunoassay, and reproductive status by gonadal histology. The results of this work clearly indicate that short periods of exposure to high water temperatures disrupt pejerrey reproduction. This effect was observed in spawning activity, at the histological level, and in the reduction of plasma estradiol in females and testosterone in males. The mRNA levels of GtH subunits and GtH receptors generally decreased in proportion to the increase in temperature for both sexes. However, the differences between groups were statistically significant only for LH-b and for FSH-R expression in pejerrey females. Thus, the gonads of pejerrey appear to be the primary target of high water temperature. Analysis of the air temperature in this region over the past 40 yr indicated an increase of 1.74C in mean annual temperature. This increase, coupled with themechanism of high-temperature sensitivity shown in this study, may be one of the reasons for the decline in pejerrey populations observed in this region over recent decades.