Associative learning and memory duration of Trichogramma brassicae

Abstract

Learning ability and memory duration are two inseparable factors which can increase the efficiency of a living organism during its lifetime. Trichgramma brassice Bezdenko (Hym.: Trichogrammatidae) is a biological control agent widely used against different pest species. This research was conducted to study the olfactory associative learning ability and memory duration of T. brassicae under laboratory conditions. According to our results, T. brassicae showed olfactory learning ability in response to conditioned odors, and this learned olfactory stimuli lasted for 20 hours. In a second experiment, the effects of frequent experiences on the memory duration of females were studied. A direct relationship between frequent experiences and memory duration was observed. When exposed to a conditioned odor, wasps’ memory duration increased in response to the number of experiences. Memory was observed at 28 h after one extra conditioning. The duration of the associative memory lasted 42 hours when 2 extra experiences were given, 50 hours after 3 experiences, and 58 hours after 4 extra conditioning experiences. Our results showed that T. brassicae can associate new odors to host existence, and they will show increased memory duration after multiple experiences.