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

Abstract

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 (19 degrees C) and two experimental temperatures (23 degrees and 27 degrees C) 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 beta, luteinizing hormone beta (LH-beta), glycoprotein hormone alpha, 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-beta 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 1.74 degrees C in mean annual temperature. This increase, coupled with the mechanism 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.

Effects of climate change on fish reproduction and early life history stages

“…Similar effects are seen in non-salmonids, with wolffish, Anarhichas lupus, showing reduced plasma levels of T and E 2 , retarded ovulation, and reduced fertility and survival , red seabream, Pagrus major, showing inhibition of expression of genes coding for arom and 11b-hydroxylase (which mediates the conversion of T to 11KT) , and freshwater pejerrey, Odontesthes bonariensis, showing reduced plasma levels of E 2 in females and T in males (Soria et al 2008). At higher levels in the HPG axis, red seabream exposed to typical summer temperatures (that truncate normal spawning) showed reduced central expression of genes for GnRH and its pituitary receptor, and reduced pituitary expression of the b-subunit gene for LH (LHb) .…”

“…At higher levels in the HPG axis, red seabream exposed to typical summer temperatures (that truncate normal spawning) showed reduced central expression of genes for GnRH and its pituitary receptor, and reduced pituitary expression of the b-subunit gene for LH (LHb) . Similarly, pejerrey displayed reduced expression of LHb and the receptor for FSH in females exposed to moderate elevations in temperature (Soria et al 2008). There is also some evidence that high temperature may interfere with the transduction of photoperiod signals to the reproductive axis, although as noted earlier, the mechanism in fish is still not well understood.…”

Effects of Water Temperature on Gonad Development in the Cold-Water Fish, Kumgang Fat Minnow <i>Rhynchocypris kumgangensis</i>

“…trout (Pankhurst et al 1996). Spawning activity and the mRNA expression levels of gonadotropins were impaired by elevated water temperatures in both sexes of the pejerrey (Elisio et al 2012, Soria et al 2008. Water temperature elevation during the spawning season increased the proportion of unfertilized and abnormally dividing eggs in the whitefish, Coregonus lavaretus, leading to increased mortality of early-stage fish (Cingi et al 2010).…”

Underground water affects sexual behavior and gene expression of hormones related to reproduction in blue gourami males

“…The environmental effect on hormones that regulate reproduction and growth in fish has been studied extensively, focusing particularly on photoperiod [1,2], temperature [3][4][5][6][7][8][9][10], water quality [11], salinity [12,13] and diet [14].…”