Heat and starvation induced hormesis in longevity of Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae) adult females

Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae) is an important endoparasitoid of Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) larvae and pupae. Previous studies have showed that environmental stress induced hormesis in a variety of organisms. In the present study, we investigated the effects of heat and starvation stress on the survival and induced hormesis in longevity of O. sokolowskii adult females under laboratory conditions. Results showed that temperature and exposure time significantly affected the survival rate of O. sokolowskii adult females with the extreme temperatures and/or longer durations proving to be more lethal. When O. sokolowskii adult females were heat-treated for 0.5, 1, 2, 4, and 8 h, LTemp₅₀ were >50.00, 43.24, 38.82, 38.32, and 38.17 °C, respectively. LTime₅₀ at the threshold temperature of 38 °C was 3.90 h. The sub-lethal temperature exposure for a certain time period reduced the survival numbers, but increased the longevity of survived adult females at the condition of starvation. The exposure for 2 h at 36 and 38 °C reduced the survival numbers by 26.67% and 46.67%, but extended the longevity of the survived adult females by 65.89% and 55.37% in comparison with those in the control, respectively. These results suggest O. sokolowskii adult female has the potential of thermal resistance, and its longevity will increase via heat and starvation treatment.