Aberrant octanol dehydrogenase isozyme patterns in interspecific Drosophila hybrids

A maternal octanol dehydrogenase (ODH) isozyme pattern is observed in embryos of reciprocal crosses of A and B variants both in intraspecific hybrids of D. pellewae and of D. metzii, respectively, and in interspecific hybrids of D. metzii crossed with either D. pellewae or D. leticiae. In addition, slowly migrating ODH isozymes not detectable in unfertilized eggs or single adult females can be seen in both intra‐ and interspecific hybrid embryos. In reciprocal intraspecific hybrids of D. pellewae, the slowly migrating embryonic isozymes appear as early as two and one half hours after fertilization, before the gastrula stage. They are presumably synthesized by pregastrula embryos. The present work supports the idea that in intraspecific hybrids of D. pellewae, maternally and paternally derived ODH genes become active at about the same time, producing a triplet isozyme pattern at positions 3, 4, 5 in late first instar larvae. The 3, 4, 5 pattern is maintained through second and third instar larvae and pupae. In adults isozymes at positions 6 and 7 often appear. The sequence of developmental changes normally observed in ODH isozyme patterns is retarded in interspecific hybrids, and aberrant patterns occur in some individuals. Sometimes early embryonic patterns persist in both B ♀/A ♂ and A ♀/B ♂ interspecific hybrids as late as the pupal stage. Either a paternally or maternally introduced ODH structural gene expected to contribute subunits to the 4 and 5 isozymes may fail to do so to a detectable degree. Other abnormalities seen in interspecific third instar larvae or pupae include a 3, 4 or 4, 5 pattern where a 3, 4, 5 triplet is expected. Gene action leading to the abnormal isozyme patterns is discussed on the basis of the tetramer hypothesis of ODH (Pipkin, '69).