Patterns of genetic mosaicism in the antennae and legs of Habrobracon juglandis

Abstract

Habrobracon females which are homozygous for the mutant ebony produce a high frequency of mosaics in their progeny. This is probably due to a delay in the migration of pronuclei, which may result in a prefertilization cleavage of one or both of them. The mosaics are zygogenetic-androgenetic, zygogenetic-gynogenetic, or gynogenetic-androgenetic in origin. The distribution of phenotypes in the adult mosaics is nonrandom, probably corresponding to the original relative positions of the pronuclei. Mosaicism patterns were studied in the legs and antennae, both of which show longitudinal clonal patterns presumably resulting from oriented cell divisions during development. Mosaicism frequencies for the appendages are similar to those found in Drosophila, indicating that the imaginal discs are initiated as similar-sized groups of cells in the two insects. The Habrobracon antenna shows sexual dimorphism, containing 19 flagellar segments in the male and 12 in the female. Gynandromorphic antennae contain male, female and mixed segments, but female segments are never found distal to the twelfth segment. The gynandromorphic antennae show a high frequency of incomplete or helical segments, occurring most frequently in segments 10–13. The data are discussed in relation to the problem of appendage segmentation.