Responses of the life history strategies in bdelloid rotifer Rotaria rotatoria to changes in temperature and food density

Temperature and food density have always been important factors in the growth and reproduction of zooplankton, however few studies attempted to reveal the effects of the two factors on the life history strategies in bdelloid rotifers. In this study, the effects of temperature (24, 28 and 32℃) and food density (0.5×106, 1.0×106, 2.0×106 and 4.0×106 cells/ml) on the growth, survival and reproduction of the bdelloid rotifer Rotaria rotatoria were explored based on the life table. The results showed that temperature had a significant effect on all life history parameters of the rotifer, and the food density as well as interaction of food density and temperature significantly affected the duration of major developmental stages and life expectancy. Regardless of what level the food density was, with the rise of temperature, the development of rotifers was accelerated, accompanied by the shortened reproduction period, reduced life span, and the time when the age-specific survivorship begins to decline gradually moved forward, and the decreasing speed was accelerated, but the intrinsic rate of population growth was increased, which is supposedly attributed to the energy trade-off in the life history strategy of the rotifers under adverse conditions. At lower temperatures (24 and 28℃), the duration of major developmental stages of the rotifers decreased with increasing food density, but high food density was beneficial to rotifers at high temperatures (32℃), and increasing of algae density prolonged the reproduction period and life span in rotifers. Accordingly, it could be concluded that at the suitable culture temperature, the lower algae concentration is conducive to the growth and reproduction of the rotifer, while high food density is necessary to ensure sufficient nutrition and energy for rotifers at higher temperature. At lower food densities, the effects of temperature on the life history parameters of the rotifers were more pronounced, indicating that food density is an important limiting factor, and the limitation or deficiency in food quantity will increase the cost of physiological regulation in basal metabolism of rotifers, thus weaken its tolerance to other factors. © 2019 by Journal of Lake Sciences.