Female Remating in Drosophila ananassae
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The Continuous Confinement Design
In this experiment the following stocks were used: DP (wild type), ca
(claret eye), ct rb (cut wing, ruby eye color—recessive mutation on the X
chromosome), y ( yellow body color—recessive mutation on the X chromo-
some). Crosses 4-7 (Table I) were used in this design. In each cross 7-day-old
virgin females and males were pair-mated in individual food vials. Males were
aspirated out within 1 h of the completion of copulation. All mated females
were stored in a group of six females per vial. The next day the same density
conditions were set up as in the 2-h daily observation design. These density
treatment vials were left undisturbed at room temperature (approx. 24oC)
for 5 days. At the end of that time the flies in all vials were etherized, and the
females were put individually into fresh food vials. Males were discarded. The
females were subcultured once in fresh food vials, 3 days later. A female was
indentified as having remated by the presence of second male types among
her progeny.
To test whether there is a significant difference in the number of re-
mated females at different densities, the data were analyzed by calculating
the chi-square values from an R × C contingency table and the correlation
coefficient (r).
RESULTS
The results of the 2-h daily observation remating and continuous con-
finement remating experiments, conducted to test the effect of density on
female remating frequency in D. ananassae, are presented in Table II. In the
2-h daily observation design there are three crosses in total. In cross 1 there
are two replicates with wild-type females and males (Bhutan). The frequency
of female remating at all four densities in cross 1 shows little variation, which
is statistically not significant [correlation coefficient (r) between density and
remating frequency: Replicate I, r = -0.753, df = 2, P > 0.05; Replicate II,
r =-0.102,df=2,P> 0.05]. In crosses 2and 3, in which ca mutant females
were tested with wild-type and mutant males (DP and ca), there is a con-
siderable increase in the frequency of female remating at higher densities,
which is statistically significant (correlation coefficient between density and
remating frequency: cross 2, r = 0.978, df = 2, P < 0.05; cross 3, r = 0.952,
df = 2, P < 0.05).
In continuous confinement, there are four crosses in total (Table II). In
crosses 4 and 5 ca mutant females were tested with wild-type and mutant
males (DP and ca) at different densities. In these crosses also there is a
significant increase in the frequency of female remating at higher densities