Dynamic changes in cold hardiness, high-temperature tolerance and trehalose content in the onion maggot, Delia antiqua (Diptera: Anthomyiidae), associated with the summer and winter diapause.

Abstract

Changes in cold hardiness, high-temperature tolerance and trehalose content in the onion maggot, Delia antiqua (Diptera: Anthomyiidae), associated with the summer and winter diapause were investigated. Survival of summer- and winter-diapausing pupae after a 15 day exposure to −15°C was greater than 80%, while less than 5% of non-diapausing pupae survived the same treatment. Greater than 80% of winter-diapausing pupae survived −23°C for 15 days, but survival of summer-diapausing pupae at the same procedure was less than 30%. More than 75% of summer- and winter-diapausing pupae, but not non-diapausing pupae, tolerated 35°C for 15 days. Trehalose concentrations in summer- and winter-diapausing pupae were not high at the beginning of diapause (≈5 μg/mg), but increased gradually and reached 10 μg/mg in 40 days, although they were kept at relatively high temperatures of 25°C (summer diapause) or 15°C (winter diapause). Cold hardiness of pupae, however, was not proportional to their trehalose content; although trehalose concentrations in winter- and summer-diapausing pupae at day 40 (WD40 and SD40) were similar (≈10 μg/mg), cold hardiness of these pupae differed largely (WD40>SD40).