Light Synchronization of the Daily Spawning Rhythms of Gilthead Sea bream (Sparus aurataL) Kept under Different Photoperiod and after Shifting the LD Cycle

Effects of Continuous Light on the Reproductive System of European Sea Bass Gauged by Alterations of Circadian Variations during Their First Reproductive Cycle

“…However, the 24 h rhythmicity did appear to be altered. 12 In the present experiment, pituitary sbGnRH levels under NP conditions did not vary over 13 the 24 h cycle, except in May, i.e., during the PSpm stage. Therefore, our results do not agree with 14 those of Bayarri et al (2004), who found significant daily variations near spermatogenesis 15 (December) in male sea bass kept in sea cages.…”

“…In our experiment, the 11 circadian variation in LH under LL was only significant during PSpg (September) and PSpm (May). 12 The highest values throughout the reproductive cycle were recorded during Spm (10-15 µg/mg prot) 13 under both light treatments. The lack of studies regarding daily and annual pituitary LH rhythms in 14 other species makes it difficult to undertake any further comparisons with our results.…”

“…Artificial photoperiods have been reported to be an 2 effective method for delaying sea bass puberty (Zanuy et al, 2001) and/or altering spawning time 3 (Carrillo et al, 1993). In later studies (Rodríguez et inhibiting early precocity (Beghtashi et al, 2004), and for dramatically reducing the levels of 13 several reproductive hormones (Rodríguez et al, 2005). However, and despite their importance, no 14 data are yet available concerning the daily rhythms of reproductive hormones in fish kept under LL.…”

“…The physiological functions of 8 living organisms have adapted to occur at those moments of the day, and also year, when the 9 probability of success is the highest (Foster & Kreitzman, 2004). Cyclic changes in environmental 10 factors are responsible for the generation of biological rhythms in organisms, with photoperiod 11 being the most important cue in entraining these rhythms as exemplified by a recent study involving 12 light synchronization of the circadian rhythm of spawning in gilthead sea bream (Mesequer et al, 13 2008). Therefore, the study of reproductive hormone circadian variations may provide interesting 14 information that could contribute to a better understanding of reproductive function of fish and 15 other species.…”

“…The fish were kept under a natural temperature regime throughout the experiment 25ºC), with the daily oscillation within a range of 0.5ºC. Light in each tank was supplied by 11 tungsten bulbs (PAR38Pro, Philips, Madrid, Spain) providing 650-700 lux at the water's surface, 12 and the simulated natural photoperiod was controlled by an electronic clock (ORBIS, Madrid, 13 Spain), programmed weekly according to local geographical coordinates. Experimental procedure 21 The objective of this experiment was to analyze the effects of LL on the daily variation of 22 reproductive hormones and precocity of male European sea bass during their first year of life.…”