Larva-induced egg hatch inhibition
Eggs within the genera Ochlerotatus and
Aedes are capable of refraining from hatching when
their environment is crowded with large larvae. We have
shown this in laboratory situations (below, Livdahl et al.
1984) and field experiments (below, Livdahl and Edgerly
1987) with O. triseriatus. We also have laboratory
evidence that this phenomenon occurs in A.
albopictus and A. aeqypti, and that larvae
inhibit eggs interspecifically with differential
intensities and egg sensitivities (Edgerly et al. 1993).
Hatch rates of Ochlerotatus triseriatus eggs
immersed in treeholes that had been stocked with fixed
densities of O. triseriatus larvae in August,
1986, pooled across four immersion periods (2, 4, 8, 16 d).
There were no significant differences for diffent time
intervals, probably because the eggs quickly entered
diapause.
This novel interspecies interaction may have implications
for the invasion of North America by A.
albopictus, which showed the lowest sensitivity to
high densities of larvae as well as the most inhibitory
larvae. The mechanism of this inhibition is thought to be
grazing of microbes from egg surfaces by larvae, which may
remove the source of oxygen depletion that is necessary to
stimulate egg hatch (right, Edgerly and Marvier 1991).
Inhibition of egg hatching may provide a mechanism for the
unhatched egg to choose a time for hatching that minimizes
potential competition with larger larvae, as well as
possible cannibalism by larger larvae.