In contrast to wild type flies, prosV1 mutant flies do not exhibit any courtship defects in the presence of (S,Z,Z)-CH503 (a more potent stereoisomer of the gustatory sex pheromone CH503).
Heterozygous males initiate a robust heterosexual courtship of mature wild-type CantonS females as early as 11 hours old (wild-type CantonS males start courting mature females at 17 hours old). The mutant males also mate earlier than control males: when 21 hours old, 14% of mutant heterozygous males mate during the first 10 minutes and 45% mate during the first 60 minutes (wild-type CantonS males initiate copulation only when 28 hours old).
The median lifespan for prosV1 animals (the age after egg laying at which 50% of homozygotes have died) is days at 25oC. Mutant animals show an extended duration of preimaginal development, with the period between the beginning of the second larval instar and the beginning of pupariation lasting 170.4 +/- 15.2 hours in the mutant animals (compared to 103.2 +/- 1.0 hours for CantonS).
Homozygous third instar larvae show reduced locomotor activity compared to controls.
Homozygous second instar larvae are indifferent to 0.1M sucrose and to 0.3M NaCl in a taste response assay, in contrast to wild-type larvae which are significantly attracted by sucrose and significantly repulsed by NaCl.
The neuromuscular junction of muscles 6 and 7 of the second abdominal segment of mutant larvae shows a very poorly arborised pattern compared to that of wild type; although the main branch of the motor axon has roughly the same length in both mutant and wild type, it has significantly fewer secondary ramifications in the mutant larvae, and the few secondary ramifications that are present are very short compared to wild type.
The courtship index of heterozygous males towards decapitated Canton-S males is significantly higher than that of wild-type males towards decapitated Canton-S males.
Homozygous larvae and pupae are smaller than heterozygotes or wild-type larvae. Mutant larvae do not show any obvious abnormal movements, digging or feeding behaviours. Homozygotes die between the second larval instar and late pupal stages. The lethality is affected by temperature and feeding conditions. At 25oC, approximately 83% of homozygotes die before reaching puparium formation, 5-12% die during pupal life and 5-12% of adult escapers die during the first 2 days of adult life. The surviving escapers have difficulties standing up and therefore show no visible locomotor activity. At 20o or 29oC, no homozygous adults eclose and 95-98% of homozygotes die as larvae. Larvae that are transferred to fresh food medium during the first instar stage show an increased probability of reaching puparium formation (43%) compared to siblings that are kept on the same medium throughout larval development (17%). Homozygous larvae have gustatory defects; they are unable to choose between neutral agar and agar mixed with NaCl (at 0.1, 0.3 or 0.5M), in contrast to wild-type larvae which are clearly repelled by 0.3 or 0.5M NaCl. Heterozygous larvae appear to be more sensitive to 0.5M NaCl than control larvae. Few significant differences are seen between homozygous and control larvae in response to sucrose in a gustatory response assay after 30 minutes of test. Heterozygous larvae show very contrasted responses depending on the dose of sucrose; they are repelled by 0.5M sucrose (showing a significant difference to control larvae) and are indifferent at 0.3M sucrose (their response index is significantly lower than that of control larvae). After 15 minutes of test, significant differences are seen between homozygous and control larvae in response to sucrose.
Heterozygous males show abnormal courtship behaviour; they actively court both virgin females and mature males, courting both intact and decapitated flies. The courtship index and attempts at copulation are higher towards females than males. Heterozygous females do not differ for sexual receptivity or locomotor activity when compared to control flies.
The homozygous lethality and homosexual male courtship of prosV1 heterozygotes can be rescued by mobilisation of the P{GawB} element. Rescue of the two phenotypes does not necessarily occur in the same excision line, indicating that the two characters have different genetic bases. Neither phenotype is rescued in an "all-or-none" manner.