Heterozygosity in inbred strains of the tree-hole mosquito Aedes triseriatus

Inbred stocks of the tree-hole mosquito Aedes triseriatus from four localities were developed using full-sib mating. The progress of inbreeding was followed electrophoretically at eight variable and six less variable enzyme loci. Rates of fixation of several of these loci were substantially lower than expected. Discrepancies between observed and expected fixation values were evident in the early stages of inbreeding and became larger as inbreeding progressed. Odh, Hbd, Pgm, and Hk-4 were usually not fixed. By the F12 and F14 generations of brother-sister mating, most individuals in the two lines were heterozygotes (Odh and Hbd in the TK lines and Odh, Hbd, Pgm, and Hk-4 in the TV lines). The probability of maintaining heterozygosity at several selectively neutral and unlinked loci simultaneously is very low. Odh, Hbd, Pgm, and Hbd loci are linked to lethal recessives on chromosome 2, creating a balanced lethal system which in turn accounts for the heterozygosity in these inbred mosquitoes.