Effects of temperature on the development of an arctic Collembola (Hypogastrura tullbergi)

1. Embryonic development, juvenile moulting and growth rates, and maximum size of the arctic collembolan Hypogastrura tullbergi were investigated at 5, 10 and 15 degreesC in laboratory experiments. The embryonic development was also investigated at 21 degreesC. 2. The lower temperature threshold of the embryonic development (to) was -1.3 degreesC, possibly reflecting a slight cold adaptation. The temperature of maximum development rate exceeded 21 degreesC. 3. Instar duration rate was linearly related to temperature. Growth per instar, however, was thermally dependent, giving an overall non-linear correlation between growth and temperature. This emphasizes the importance of studying growth and moulting as separate processes in Collembola. 4. Development of genital area (number of hairs) over succeeding instars was affected by the temperature, suggesting that a higher proportion of individuals reached the adult stage in an earlier instar at 15 than at 10 degreesC. 5. Contrary to the general pattern in ectotherms of increasing size at lower temperatures, adult H. tullbergi reached a larger maximum size at 15 than at 10 degreesC. 6. No aspects of postembryonic development in H. tullbergi showed any signs of cold adaptation, probably because it is more important to be able to efficiently utilize high temperatures that frequently occur in the microhabitat during sunny periods in summer.