MIRANDA Leandro Andres
Effects of daily water temperature fluctuations on brain-pituitray-gonad axis of pejerrey (Odontesthes bonariesnis) during its reproductive season
Indian Journal of Science and Technology
Indian Society for Education and Environment
Lugar: Thrisur; Año: 2011 vol. 4 p. 38 - 38
The increases noted in the temperature of many water bodies which are considered to be consequences of global warming have already started to affect fish reproduction. Pejerrey is a multiple spawner and its reproductive activity begins when water temperatures reach around 13 to15° C and peaks at temperatures between 18 to 20° C with a major spawning period during spring. Recently, it has been demonstrated that constant temperature regimes higher than 23° C impair pejerrey reproduction. In the last years, in shallow lakes from pampasic region of Argentina (the natural habitat of O. bonariensis), were reordered daily temperature fluctuations from 19° C to 27° C during some days in spring. The aim of this study was to examine the effects of short-term pulses of warm water on brain-pituitary-gonad axis of pejerrey during spawning season. Three groups of 10 fish of both sexes with external signs of active reproductive status were kept in tanks and subjected to constant 19° C (reproductive control), daily temperature fluctuation from 19 to 25° C and from 19 to 27° C. After 8 days, all fish were sacrificed and gene expression of brain GnRH variants, pituitary GtH subunits (FSH-β, LH-β, GPH-α) and gonad GtH receptors (FSH-R and LH-R) were analyzed by real-time quantitative PCR. Also, a portion of the gonad of each fish was processed by routine histological methods. Fish exposed to pulses of warm water stop to spawn and the histological analysis of their testis and ovaries showed clear signs of regression. In general, in those experimental fish it was observed that GnRHs, GtH subunits, and GtH-Rs mRNA levels decreased when compared with fish from control group. However, only pjGnRH (GnRH-I) and FSH-β in both sexes, LH-β and GPH-α in males and FSH-R in females showed statistically significant differences. The results obtained demonstrated that daily high water temperature fluctuations during spawning season suppressed the gene expression of different genes in the brain-pituitary-gonad axis blocking pejerrey reproduction.Global warming may increase the frequency of exposure to harmful temperatures causing shortening or overall disruption of spawning activity affecting pejerrey wild populations.