بومشناسی آبزیان (Oct 2017)
Integrated effects of photoperiod and light intensity on some reproductive parameters of Artemia parthenogenetica during consecutive weeks in semi-intensive culture system
Abstract
This study investigated the integrated effects of two photoperiods (16:08 and 08:16 h) along with three light intensities (3000, 15000 and 50000 lux) on some reproductive parameters and broodstock survival rates of Artemia parthenogenetica in six treatments in a completely randomized factorial design in culture system until death. Two-way ANOVA analysis revealed significant differences in total offspring production, percentage of pregnant females, offspring per broodstock and encysted-embryos percentage during different weeks between treatments. In each photoperiodic levels, increasing of illumination caused a decreasing trend in weekly offspring production. The highest offspring production was obtained in the females cultured in 3000 lux (at two photoperiods) in the first seven weeks (800-1400 offspring). In both photoperiods, increasing illumination causedirregular decreasing trend in the weekly average pregnant females. The interaction effects showed significant differences in the encysted-embryos percentage until the ninth weeks of culture. = The encystment percentage was higher in short photoperiod compared to longer period. In both photoperiods, the mean survival rates of females were the highest in 3000 lux (60-80%) compared to 15000 lux (28-55%) and 50000 lux (8-20%) at the first 45 days of culture. Accordingly, the treatment of 3000 lux-16:08 h was the ideal light level in the current experiments due to the highest offspring production and females’ survival rate as well as the increasing percentage of pregnant females (until six weeks), while the illumination of 50000 lux showed the lowest reproduction characteristics.
