Physiological
and behavioral phenomena of many animals are restricted to
certain times of the day. Many organisms show daily rhythms
in their mating. The daily fluctuation in mating activity
of a few insects is controlled by an endogenous clock. The
fruitfly, Drosophila, is the most suitable material
to characterize the genetic basis of circadian rhythms of
mating because some mutants with defective core oscillator
mechanism, feedback loops, have been isolated. D. melanogaster
wild-type display a robust circadian rhythm in the mating
activity, and the rhythms are abolished in period or timeless
null mutant flies (per01 and
tim01), the rhythms are generated
by females but not males. Disconnected (disco) mutants which
have a severe defect in the optic lobe and are missing lateral
neurons show arrhythmicity in mating activities. Thus, the
lateral neurons seem to be essential for the circadian rhythm
in mating activity of Drosophila. Furthermore, an anti-phasic
relation in circadian rhythms of the mating activity was detected
between D. melanogaster and their sibling species D.
simulans. The Queensland fruit flies or wild gypsy moth
also show species-specific mating rhythm, suggesting that
species-specific circadian rhythms in mating activity of insect
appear to cause a reproductive isolation.
