MIXIS STRATEGIES AND RESTING EEG PRODUCTION OF ROTIFERS LIVING IN TEMPORALLY-VARYING HABITATS

A dynamic model based on six differential equations has been developed to explore the control of mixis of rotifers living in temporally-vary ing habitats. The equations give variation rates of amictic females, t hree stages of mictic females, males and resting eggs. The model takes into account some constraints on mixis (e.g., male-female encounter p robability and effort involved in resting egg production) and its pred ictions have been generated by computer simulation using parameter val ues from the literature. For simulation, a time-dependent birth rate f unction was assumed to account for changes in the environment, and sev eral mixis patterns (i.e., moment of mixis induction and mictic rate i f induced) were presumed, followed by computing resting egg production . The results were very insensitive to changes in those model paramete rs associated with mixis; however, several assumptions could quantitat ively affect the conclusions. When compared with the results reported in the literature, results from our simulations suggest that the optim al mixis strategy could be very dependent on the ecological features o f the habitat. Moreover, in temporal habitats high mictic rates should be expected when the mixis is induced, and the optimal moment of mixi s induction would be few days before the mortality rate overcompensate s the birth rate of amictic females. Furthermore, the optimal strategy could be affected by informational constraints, and some degree of va riability in the moment of mixis induction, whether or not genetically determined, could be maintained in the population.