CHENG, Chia Wei*; HORNG, Shwu Bin; National Taiwan University: The mechanism and adaptation of Egg-dumping behavior of Callosobruchus maculatus

Egg-dumping is a behavior that a female lays eggs on unsuitable places under conditions of host deprivation. All these eggs will die at the very beginning of life. Furthermore, because the female does not feed as an adult, egg dumping may waste energy and thus the behavior, in the previous studies, was generally considered as a maladaptive behavior under physiological constrain. In this study, it was revealed that the numbers of dumping eggs in a population did not form a continuous distribution. Accordingly, the females could be divided into two groups�dumpers and non-dumpers. By dissecting their ovaries and comparing the life history traits of the two groups, we falsified the argument that different physiological conditions, i.e., egg maturation rate and female weight, result in the various dumping behavior of the females, and in turn influence their adaptation to the stock environment. Because the results of the above tests are discordant to previous physiological explanations, our attention was turned to what caused a female to accept an unsuitable place as a host for laying eggs. We treated the females with different host abundances, and then deprived them of host. The result showed that the egg-dumping response was relatively retarded, but not accelerated, by host-abundant experience. In addition to the retardant effect from the experience of abundant host, the observations of searching patterns were also reported in this study to support a new hypothesis that explains the egg-dumping behavior in decision-making aspect. In the decision-making hypothesis, the adaptation of egg-dumping behavior will be redefined, and therefore it can be further tested by selection-and-response experiments.