Rapid cold-hardening in Zaprionus vittiger (Coquillett) (Diptera: Drosophilidae)

Low temperature injury can be significantly reduced by pre-treatment at sub-lethal low temperatures of only a few hours--a phenomenon termed 'rapid cold-hardening' (RCH). However, most studies to date have focused extensively on only a few key insect taxa, e.g. Drosophila melanogaster within the Drosophilidae family. Further studies on other closely-related species are required to better understand evolutionary and ecological variation in the magnitude of the RCH response in terrestrial arthropods. Here, we investigated RCH in a previously unstudied fruit fly, Zaprionus vittiger, following a range of high and low pretreatment temperatures. There was a significant improvement in Z. vittiger survival of lethal temperatures (2 h at -3 degrees C) following a 2 h pretreatment at 4, 7 and 10 degrees C as well as 30 degrees C for 2 h. Maximum survival (60-70%) during RCH was achieved following hardening at 7 degrees C and 10 degrees C but is lower than some Drosophila species under similar treatment conditions. Therefore, since RCH was detected in a confamilial species, we propose that RCH might be a widely conserved response to temperature variation in the family Drosophilidae, although some variation in the magnitude of the response can be detected.