Spontaneous gynandromorphs as source materials for an embryonic fate map in Aedes togoi (Diptera : Culicidae)

Abstract

Twenty-nine spontaneous gynandromorphs in the mosquito, Aedes togoi, were analyzed in order to construct an embryonic fate map. The estimated distances on the blastula between primordial discs for the abdomen, genitalia, antenna, palp, and wing showed sufficient consistency to form the map. In Aedes, sex is determined by the sex factors M and m, with males being heterogametic and females homogametic mm. The mechanism by which a gynandromorph is produced in this insect can be ascribed to double fertilization of a binucleate egg by spermatozoa carrying different sex factors. The two nuclei undergo nuclear division and resultant nuclei form two clusters of different sexes and cover the blastoderm surface. Primordial discs are then developed after cell division. Because this process is conceived to be equivalent to that a sexual boundary separates the cells on the blastoderm at random, distances between the primordial discs of structures can be estimated from their segregation ratios of sex in gynandromorphs. The results of the present study are expected to provide a better understanding of how the mosquito gynandromorph is produced.