Activation in Vitro of Unfertilized Egg Development in Honeybee Queens

Mechanical Egg Activation and Rearing of First Instar Larvae of Sirex noctilio (Hymenoptera: Siricidae)

Egg activation is a cellular transition of an arrested mature oocyte into a developing embryo through a coordinated series of events. Previous studies in Hymenoptera have indicated that mechanical pressure can induce egg activation. In this study, we developed the first egg activation protocol for the haplodiploid insect pest, Sirex noctilio (Hymenoptera: Siricidae), from two climatically different regions in South Africa to demonstrate the broad applicability of the method. In addition, activated eggs were exposed to three treatments involving water, pine sawdust, and the fungal symbiont of S. noctilio, Amylostereum areolatum (Russulales: Amylostereaceae), to determine if the symbiotic fungus is a requirement for egg development in an artificial laboratory environment, as the symbiotic fungus has been hypothesised to be necessary for egg and early larval development in a natural environment. A rearing protocol was developed for the first instar larvae using a modified Anoplophora glabripennis (Coleoptera: Cerambycidae) artificial diet. A significant difference between the mean survival rates of activated eggs from the two different regions was observed. Amylostereum areolatum was shown to be unnecessary for egg survival and adversely affected egg eclosion in an artificial laboratory environment. The maximum larval survival duration on the artificial diet was 92 days. The egg activation and rearing protocol developed in this study enables opportunities for research on the physiology, ecology, symbioses, and genetics of S. noctilio, which can be exploited for new genetic pest management strategies.

Reorganization of the Central Nervous Systems in Response to Changes in Social Environment Among Insects

Caste is a polyphenism for efficiently accomplishing various tasks in a group for social insects, and morphological differentiation is based on nutritional conditions in larval development. Adult worker insects can plastically convert part of their internal organs and behaviors to those of a queen while maintaining external morphology as is. Behavioral change together with caste transition is caused by physiological change in the brain, and behavioral change affects even the brain morphologically, eventually creating an “adaptive” brain specialized in caste. This phenomenon, a typical example of “mobiligence,” is a model case in which physiological and morphological transitions in the brain are detected.