Rapid cold‐hardening of Drosophila melanogaster in a field setting

Abstract

Although laboratory studies demonstrate that cooling to ecologically relevant temperatures and/or at ecologically relevant rates induces rapid coldhardening (RCH) in a variety of insects, little is known of the induction of RCH in nature. In the present study, caged Drosophila melanogaster (1 -2 days posteclosion) from a colony established with flies collected locally are placed in a field setting (i.e. in approximately 4-cm deep leaf litter beneath an apple tree in Mount Pleasant, Michigan) during late afternoon (18.00 h EST; 05.00 h GMT). As the cage temperature falls from 22.1 ± 0.8 to 10.1 ± 0.1 °C between 18.00 and 06.00 h, the proportion of flies surviving a transfer to -6 °C for 1 h increases from 10.0 ± 6.2% to 68.1 ± 7.2%. When obtained from field cages, and then cooled from 23 °C at approximately 0.33 °C min −1 , more female flies remain behaviourally responsive (clinging to surfaces, exhibiting an active righting response, and/or climbing) at temperatures of 8 -12 °C (24.00 h samples) or 7 -12 °C (06.00 h samples), than do those sampled from cages kept in an incubator (23 °C). Field cooling reduces chill coma temperature from 8.7 ± 0.2 °C at 06.00 h to 7.1 ± 0.2 °C at 24.00 h, and to 6.6 ± 0.2 °C at 06.00 h. These data demonstrate that, in a recently collected culture of D. melanogaster , natural changes in microenvironmental temperature induce RCH that can benefit the organism at temperatures encountered in nature.

Rapid cold hardening improves recovery of ion homeostasis and chill coma recovery in the migratory locustLocusta migratoria

“…This also applies to first instar hoppers and adults, which might experience low temperatures in early spring or late autumn, where temperature can fluctuate by 20-40°C on a daily basis (Wang and Kang, 2003;Tanaka and Zhu, 2008). Such fluctuations could result in mortality and it is likely that the RCH effect on recovery and acute CS survival, found in this study, enhances the cold tolerance of wild locusts exposed to diurnal or unexpected decreases in environmental temperature (Chen et al, 1987;Lee et al, 1987a;Kelty and Lee, 1999;Koveos, 2001;Kelty, 2007;Overgaard and Sørensen, 2008;Denlinger and Lee, 2010). Importantly, the observed benefit of RCH on recovery and acute CS survival occurred despite the fact that hardened individuals had been exposed to cold for 4h (2h at 0°C followed by 2h at −4°C), whereas the non-hardened individuals had only been exposed to cold for 2h (at −4°C).…”

“…The RCH response might enable insects to enhance cold tolerance in response to predictable (e.g. diurnal) or unexpected decreases in environmental temperature (Chen et al, 1987;Lee and Chapman, 1987;Kelty and Lee, 1999;Koveos, 2001;Kelty, 2007;Overgaard and Sørensen, 2008;Denlinger and Lee, 2010). Using the chillsusceptible locust Locusta migratoria, the present study examined the relationship between recovery of ion homeostasis and recovery from chill coma following cold shock (CS, 2h at −4°C).…”

Phenotypic plasticity of thermal tolerance contributes to the invasion potential of Mediterranean fruit flies (Ceratitis capitata)

“…Addo-Bediako et al, 2000;Kimura, 2004). Indeed, survival responses probably form a major component of climatic stress resistance, and are used by insects to cope with temperature variation at daily timescales (Meats, 1973;Kelty & Lee, 2001;Kelty, 2007;, but significantly, also upon introduction into new environments Slabber et al, 2007;Kristensen et al, 2008;Preisser et al, 2008). Furthermore, survival is a critical first step in the invasion process, without which any further establishment through reproduction is impossible.…”

Calcium signaling mediates cold sensing in insect tissues

“…RCH has since been described in dozens of insect species (7), including both freeze-intolerant (insects in which internal ice formation is lethal) and freeze-tolerant species (insects that tolerate internal ice formation) (8,9). Naturally occurring thermoperiods can elicit RCH (10), and RCH preserves essential functions such as courtship and mating (11,12), supporting the relevance of this process to natural populations.…”