ICEBOX, A RECESSIVE X-LINKED MUTATION IN DROSOPHILA CAUSING LOW SEXUAL RECEPTIVITY

The X-linked recessive mutation icebox (ibx; 1-23, 7F1) of Drosophila melanogaster lowers the sexual receptivity of females. The probability of mating with mature wild-type males is reduced in ibx homozygotes, and the frequency of rejection behavior (rate per minute) towards cour ting males is increased. ibx fails to complement In(1)RA35, which is a lethal allele of Neuroglian (Nrg, which encodes a transmembrane prote in found in embryonic tissues including the nervous system) due to a b reakpoint in that gene; however, both l(1)B4 and l(1)VA142, other leth al mutations of Nrg, do complement ibx. 12-h ibx embryos exhibit a nor mal pattern of staining for the Neuroglian-specific antibody, Mab BP10 4. Males and females mutant for ibx have normal egg-to-adult survival and appear normal in several ''general'' behavioral traits including o lfaction, phototaxis, locomotor activity, and heartbeat. ibx males cou rt normally, and are successful in mating. These characteristics sugge st that ibx does not cause sensory or motor defects. Ovarian growth an d sperm storage are wild-type in ibx/ibx females. Treatment with the J H analog methoprene increases the receptivity of ibx/ibx females.