TABLE 1

Male courtship behavior affected by the frusat mutation

Behavior
Mutant or control male courtingGroup intermale courtship (ChI)
GenotypeIndicesAnother maleA female
frusat/frusatCI5 ± 23 ± 117 ± 2
WEI1 ± 10 ± 0(8)
(15)(13)
frusat/ChaM5CI6 ± 28 ± 427 ± 4
WEI0 ± 01 ± 1(10)
(15)(12)
frusat/P14CI16 ± 66 ± 47 ± 3
WEI4 ± 32 ± 1(9)
(14)(12)
frusat/fruw24CI8 ± 51 ± 136 ± 7
WEI1 ± 10 ± 0(10)
(12)(12)
fru+ (wild type)CI3 ± 174 ± 50 ± 0
WEI0 ± 037 ± 5(5)
(10)(10)
frusat/+CI2 ± 183 ± 20 ± 0
WEI0 ± 046 ± 3(5)
(12)(12)
  • CIs (courtship indices) ± SEM, mean percentage of time that the test males spent courting another male or a female in 5- to 10-min observation periods (see materials and methods); WEIs (wing-extension indices), mean percentage of time the males displayed wing extensions toward the other male or a female (wild type, Canton-S) during such an observation period. For male-male courtships, only the first fly to initiate courtship had his actions quantified (the other male in an observation of this kind was of the same genotype as the recorded courter). The numbers of fly pairs observed are in parentheses (first two data columns). ChI (chaining index, last data column), mean percentage (± SEM) of time at least three males of the eight (per tested group) showed courtship toward each other in a 10-min observation period; the numbers of the eight-male groups observed are in parentheses. The fru+ control values are from observations of Canton-S males and the frusat/+ control males resulting from a cross of mutation-bearing to Canton-S flies. Statistical comparisons (see materials and methods) revealed thatfrusat males courted others at the same levels as did frusat/P14, frusat/ChaM5, and frusat/fruw24 (P > 0.05 in all cases); the same kind of comparison with respect to male-with-female behavior−between the effects of frusat homozygosity and uncoverage of its effects by the Dfs–revealed no differences (P > 0.05 in all cases). Comparing the behavior of frusat/frusat and frusat/Df types (together) in terms of courting other males vs. females, there were no differences (P> 0.05 in all cases). In the male-with-male tests, these mutant types courted other males at the same levels as did wild-type or frusat/ + males (P> 0.05 in all cases). During a total of ca. 9 min, during which time frusat/frusat and frusat/Df males extended their wings toward females or males (given the WEI values in the first two data columns), no song pulses were recorded, whereas fru+ -bearing males generated 200-400 pulses per minute (Villella et al. 1997). From the current recordings of male-male pairs, only four homozygous frusat males displayed wing extensions toward another male (out of 15 mutant individuals tested). Two of these four males generated only brief low-amplitude sine-song bouts; such humming sounds were within the normal frequency range (cf. Villella et al., 1997). Although homozygous frusat males showed little interest in wild-type females, in 2 of the 13 cases, the male followed, oriented, and displayed wing extensions toward the female, but produced no sounds. Statistical comparisons of ChIs revealed that homozygous frusat males chained as much as frusat/ChaM5 and frusat/fruw24 did (P = 0.09 and 0.07, respectively); frusat/P14 males chained significantly less than homozygous frusat males (P = 0.02). Additional observations, made at high magnification to determine whether steps in the courtship sequence occurred in addition to those tabulated, showed that 7 of 20 frusat/frusat males tested with females initiated courtship by tapping the latter with their foreleg. Two of these seven executed a late step in the sequence by attempting to lick her abdomen with proboscis extension; one mutant male licked with genital contact. None of the 20 frusat males attempted copulation. All wild-type males (n = 10) tested with females tapped, licked (7 of 10 with contact), and attempted copulation. The high-magnification observations of frusat male pairs (n = 15) showed that 14 of the test individuals (the “courters,” defined as above) exhibited tapping behavior; 7 of 14 proceeded to licking (1 of 7 with contact), and no attempted copulation was observed.