Basal tolerance to heat and cold exposure of the spotted wing drosophila,Drosophila suzukii

Abstract

The spotted wing Drosophila, Drosophila suzukii, is a new pest in Europe and America which causes severe damages, mostly to stone fruit crops. Temperature and humidity are among the most important abiotic factors governing insect development and fitness. In many situations, temperature can become stressful thus compromising survival. The ability to cope with thermal stress depends on basal level of thermal tolerance. Basic knowledge on temperature-dependent mortality of D. suzukii is essential to facilitate management of this pest. The objective of the present study was to investigate D. suzukii basal cold and heat tolerance. Adults and pupae were subjected to six low temperatures (−5–7.5 °C) and seven high temperatures (30–37 °C) for various durations, and survival-time-temperature relationships were investigated. Data showed that males were globally more cold tolerant than females. At temperature above 5 °C, adult cold mortality became minor even after prolonged exposures (e.g., only 20% mortality after one month at 7.5 °C). Heat tolerance of males was lower than that of females at the highest tested temperatures (34, 35 and 37 °C). Pupae appeared much less cold tolerant than adults at all temperatures (e.g., Lt50 at 5° C: 4–5 d for adults vs. 21 h for pupae). Pupae were more heat tolerant than adults at the most extreme high temperatures (e.g., Lt50 at 37 °C: 30 min for adults vs. 4 h for pupae). The pupal thermal tolerance was further investigated under low vs. high humidity. Low relative humidity did not affect pupal cold survival, but it reduced survival under heat stress. Overall, this study shows that survival of D. suzukii under heat and cold conditions can vary with stress intensity, duration, humidity, sex and stage, and the methodological approach used here, which was based on thermal tolerance landscapes, provides a comprehensive description of D. suzukiithermal tolerance and limits.

Mechanisms underpinning the beneficial effects of fluctuating thermal regimes in insect cold tolerance

“…Boardman et al, 2013), and variation of RH that accompanies FTR may directly affect insects' cold survival as well. Indeed, high humidity can promote cold survival of Drosophila at some temperatures (Kobey and Montooth, 2013), but this is not always true (Boardman et al, 2013;Enriquez and Colinet, 2017). FTR experiments should be explored at both constant and variable levels of RH to disentangle the effects of each.…”

Effect of short-term high-temperature exposure on the life history parameters of Ophraella communa

“…Both basal tolerance and plastic responses contribute to the ability of ectotherms to counter heat stress 29 . Behavioural thermoregulation allows mobile stages (like larvae and adults) to escape lethal temperatures, and less mobile stages (like eggs and pupae) thus have to cope with and tolerate more extreme conditions than mobile stages 30 . According to this principle, immobile stages are expected to show higher basal thermotolerance than mobile stages 28 – 30 .…”

“…Behavioural thermoregulation allows mobile stages (like larvae and adults) to escape lethal temperatures, and less mobile stages (like eggs and pupae) thus have to cope with and tolerate more extreme conditions than mobile stages 30 . According to this principle, immobile stages are expected to show higher basal thermotolerance than mobile stages 28 – 30 . Any developmental stage of insect species with relatively short generation periods may experience heat stress in the field, thus the population sizes of these species may be affected.…”

Fluctuating thermal regime preserves physiological homeostasis and reproductive capacity in Drosophila suzukii

“…1). These temperature regimes were chosen based on previous experience showing that 20 °C is a benign temperature and that 3°C causes the flies to enter a cold coma and where chill injury gradually develop (Enriquez et al, 2018;Enriquez and Colinet, 2017).…”

“…Insects used in biological control are often stored at low temperatures as this limits senescence and reduces the labour associated with maintenance. However, most Drosophila species, including D. suzukii, are chill-susceptible, and succumb during chronic exposure to low or even mild temperatures (Andersen et al, 2015;Dalton et al, 2011;Enriquez and Colinet, 2017;Jakobs et al, 2015;Kimura, 2004;MacMillan et al, 2015b;Plantamp et al, 2016;Ryan et al, 2016). When chill susceptible Drosophila are exposed to chronic low temperature they decrease their activity and if the temperature is sufficiently low they enter a coma.…”