Inflexible versus flexible: the influence of temperature and photoperiod on pre‐ and post‐eyespot development time in Libellulidae (Odonata)

Abstract

AbstractTemperature and photoperiod are important environmental parameters for organisms. The present study tests the hypothesis that, during embryogenesis, temperature and photoperiod influence pre‐ and post‐eyespot development time in dragonflies of the family Libellulidae differently. Eggs are used from eight species (five different genera, from Africa/Europe, and lentic/lotic habitat preferences). The eggs are reared under different constant or fluctuating temperature and light conditions. There are no general species‐specific degree‐days for pre‐ or the post‐eyespot development in these species. In all study species, the variance within and between the treatments of the duration in days and the degree‐days of pre‐eyespot development is lower than that of post‐eyespot development. Pre‐eyespot development appears to be less flexible in its reaction to environmental influences. By contrast, post‐eyespot development appears to react more flexibly to environmental influences. All eight species show the same pattern. This indicates strongly that this flexibility is a general pattern in Libellulidae that might help the species within this family to cope successfully with variations in environmental conditions. Because eyespot development and katatrepsis occur close to each other, the above‐described pattern might also appear in other odonates and in other insect groups that exhibit katatrepsis. For all of them, it is essential for survival to match the time of hatching with adequate external temperature and photoperiodic conditions.