Growth of Agapetus fuscipes larvae related to water temperature

R.C. Nijboer.Alterra, P.O. Box 47, 6700 AA Wageningen, The Netherlands

Climate change might influence the life cycle of species. In this study we tested whether growth of Agapetus fuscipes larvae is influenced by temperature. In four streams, temperature was measured each 15 minutes during 14 months. Fortnightly, 6 samples of A. fuscipes were taken and their head capsule width was measured. In two streams the temperature varied between 6 and 12 °C and in two streams between 4 and 16 °C. In the streams with high summer temperature, A. fuscipes grew faster, survived the winter in a higher larval instar and pupated earlier.

In the laboratory, larval growth was measured at 8, 12 and 16 °C. Animals from streams with low summer temperature showed larger head capsule widths at higher temperatures. Animals from the streams with high summer temperature showed less growth and no difference in head capsule width when comparing 12 with 16 °C, probably because they were already further in their development before the experiment started. The number of pupae was high at 16 °C, in particular for the animals from the streams with high summer temperatures.

In conclusion, growth and timing of the life cycle depend on the water temperature in the stream.