EXTENDED REPRODUCTIVE ROLES OF THE FRUITLESS GENE IN DROSOPHILA-MELANOGASTER REVEALED BY BEHAVIORAL-ANALYSIS OF NEW FRU MUTANTS

The fruitless mutants fru(3) and fru(4) were assessed for sex-specific reproductive-behavioral phenotypes and compared to die previously rep orted fru mutants. Among the several behavioral anomalies exhibited by males expressing these relatively new mutations, some are unique. fru (3) and fru(4) males are less stimulated to court females than fru(1) and fru(2). No courtship pulse song is generated by either fru(3) or f ru(4) males, even though they perform brief wing extensions. fru(3) an d fru(4) males display significantly less chaining behavior than do fr u(1) males. The hierarchy of courtship responses by fru males directed toward females vs. males, when presented with both sexes simultaneous ly, is that fru(1) males perform vigorous and indiscriminant courtship directed at either sex; fru(4) males are similarly indiscriminant, bu t courtship levels were lower than fru(1); fru(2) males prefer females ; fru(3) males show a courtship bias toward males. fru(3) and fru(4) m ales essentially lack the Muscle of Lawrence (MOL). On several reprodu ctive criteria, there was no difference between fru-variant females an d fru(+). The increases in phenotypic severity measured for the new mu tants are discussed in the context of the emerging molecular genetics of fru and with regard to the gene's position within the sex-determina tion pathway.