Developmental rates for Wuchereria bancrofti larvae
maturing in the vector Aedes polynesiensis were estimated by analysing
stage-frequency data consisting of counts of larval stages in mosquitoes
reared
at 20, 22·5, 25, 27·5, 30 and 32 °C. Base
temperatures (i.e. low temperature thresholds) for W. bancrofti
development
were estimated by the x-intercept method
and the model of Lactin et al. (1995). Resulting values were similar
with
both methods and were ≈12·5 °C for microfilariae
(mf) in thorax, ≈17 °C for L1, 15·5 °C
for L2 and 16·5 °C for L3. Upper
thresholds estimated by the Lactin et al. model
were 29·3 °C for mf, 29·1 °C for L1, 32·2
°C
for L2 and 31·5 °C for L3.
In addition, an original method was devised for
computing the L3 upper threshold, by modelling L3 length shrinkage with
temperature. It gave a value of 31·4 °C. At
32 °C, L2 and L3 stages exhibited altered morphology, larvae being
shorter
and wider than expected. The model of Lactin
et al. described adequately the non-linear relationship between
developmental rate and temperature, but a linear degree-day
approach may be applied for temperatures below 27–28 °C.