Effect of starvation and accumulation of generations on mixis induction in offspring of the monogonont rotifer Brachionus manjavacas hatched from resting eggs

Abstract

The effect of starvation on sexual reproduction in cyclic parthenogenetic rotifers has been studied using life history experiment. Short-time starvation of rotifers that experienced starvation immediately after hatching from resting eggs can cause high induction of sexual reproduction up to the 10th generation. However, it is not clear whether the induction of sexual reproduction can occur beyond the 10th generation. To investigate this phenomenon, we conducted a sex induction study using the monogonont rotifer Brachionus manjavacas. Newborn stem females were starved for 12 h, while controls were supplied with 7.0 × 106 cells ml−1 of Nannochloropsis oculata. In a life history experiment, the rotifers were individually cultured in 96-well microplates containing 0.2 ml of seawater (22 ppt) in each well at 25 °C with daily feeding thereafter. Mixis induction in offspring from starved stem females was significantly higher than in those from non-starved stem females up to the 40th generation. The effect of accumulative generations increased mixis induction up to the 20th generation. Effect on future generations of the rise in mixis ratio by the starvation to stem females may facilitate colonization by favoring population growth via female parthenogenesis and by decreasing food requirements for survival and reproduction.