Early memory in the parasitoid wasp Nasonia vitripennis
We studied early memory in Nasonia vitripennis, a parasitoid of fly pupae and emerging model organism for ecological questions in the context of learning. After associative training consisting of one drilling experience in a host in the presence of cinnamon, females showed a preference to cinnamon for at least 24 h. To study sensitisation, wasps were trained by one drilling in a host without cinnamon. These wasps were not attracted to cinnamon immediately afterwards. Obviously, sensitisation is not involved in early memory. Wasps that were anaesthetised by CO2 directly after associative training did not react to cinnamon 30–45 min later, but after 1 and 24 h. CO2 treatment ≥5 min after training did not erase the reaction to cinnamon. This indicates the existence of four early memory phases. (a) One phase <5 min after training, in which CO2 has to be applied to become effective. (b) One subsequent phase which is resistant to CO2. (c) One phase <1 h in which memory can be erased by CO2 treatment directly after training. (d) One phase 1–24 h not affected by CO2 treatment. Together with earlier data this enables us to establish a complete memory structure for N. vitripennis.