STRAINS OF DROSOPHILA-MELANOGASTER DIFFER IN ALCOHOL TOLERANCE

The influence of environmental ethanol on different fitness components and the larval activities of some enzymes were studied in three strai ns of Drosophila melanogaster. All three strains carried the Adh(S)-al pha Gpdh(F) allele combination on their second chromosomes while they had unique allele combinations at the Odh and Aldox loci on their thir d chromosomes (strain 1: Odh(S)-Aldox(F); strain 2: Odh(F)-Aldox(S); s train 3: Odh(S)-Aldox(S). Normal lines and exposure lines, kept on 5% ethanol supplemented medium for at least 20 generations, were establi shed from each strain and the responses of the two lines to different ethanol concentrations were compared. Two survival components were est imated in the juvenile life history stages. In addition, the weights o f the emerging adult males were measured at various concentrations of ethanol. The changes in the activities of two enzymes (ADH and alpha G PDH) were also surveyed in the larvae after the different ethanol trea tments. Strain-specific differences were observed in the responses of all investigated traits to ethanol. Odh(S)-Aldox(F) larvae seemed to b e more tolerant to ethanol than the larvae of the other two strains wh ile the utilisation of ethanol as energy source appeared to be the lea st effective in this strain. Larvae of the exposure lines had signific antly higher tolerance to ethanol, and the adult males were heavier th an the ones from the normal lines. The enzymatic responses of the two lines to the ethanol treatments were also different. ADH activity, fre sh male weight, and pupa-to-adult survival seemed only to be associate d under short-term exposure to ethanol. Ethanol tolerance appeared to be independent of the utilisation of ethanol in the larva-to-pupa stag e.