Effects of cold stress during diapause on the survival and development ofDelia radicum (Diptera: Anthomyiidae) in England

Abstract

Exposing diapausingDelia radicum (L.) to temperatures from-10.2 to-14.8° C during a 80-day experimental period reduced survival to eclosion and the rate of postdiapause development. No such effects occurred among those exposed to-7.1° C for up to 80 days. A continuous exposure to-10.2 or-14.8° C reduced survival of overwinteringD. radicum by the same amount as an equal duration of exposure to these temperatures interrupted by 14 days at 2° C, indicating that the effects of cold exposure were additive and that repair of cold-induced injuries did not occur at 2° C. The decreased survival with increasing duration of exposure to-10.2 or-14.8° C were described by the equations:[Formula: see text] Wherep=the proportion surviving to eclosion andt=the number of days of exposure to the temperature given by the subcript. An increased incidence of malformed adults was associated with low survival. Adult emergence occurred within two periods. Early-emerging flies required up to 230° D and late-emerging flies more than 330° D above 5.6° C. Among early-emerging flies, a reduced rate of postdiapause development was associated with low survival but the development of late-emerging flies was not affected.OverwinteringD. radicum parasitized byTrybliographa rapae (Westw.) or byAleochara bilineata Gyll. responded similarly to unparasitizedD. radicum although those parasitized byT. rapae were less resistant to cold injury when exposed to-14.8° C. D. radicum and its parasitoids are capable of surviving temperatures more severe than those normally occurring in England and Wales; and, therefore, cold injury is unlikely to affect their population dynamics.

The sub-lethal effects of repeated freezing in the woolly bear caterpillar Pyrrharctia isabella

“…This implies that, rather than a constant threat of mortality, each freezing event causes caterpillars to accumulate injuries that are not fully repaired and consequently increases the likelihood of being killed by subsequent freezing events. Similarly, in the fly Delia radicum and the moth Mamestra configurata, repair from extreme cold stress does not take place even with 4weeks recovery time (Turnock et al, 1983;Turnock et al, 1985).…”

To Freeze or Not to Freeze? An Evolutionary Perspective on the Cold‐Hardiness Strategies of Overwintering Ectotherms

“…Because of this physical characteristic, all living organisms (even tropical ones) exhibit greater or lesser supercooling capacities. However, a thermal environment leading to a supercooled state imposes physiological stress that may reduce winter survival (e.g., overwintering aphids are killed within a few minutes at temperatures of -5Њ to -15ЊC, although their SCP is -25ЊC; Pullin and Bale 1988) as well as future life-history traits (e.g., lower postdiapause development rate for dipteran and lepidopteran larvae exposed to subzero temperatures; Turnock et al 1985;Turnock and Bodnaryk 1991). In our model, such stress is represented by S A , and, not surprisingly, the freeze-avoidance strategy is favored by a low value of this parameter.…”

“…For freeze avoidance, various laboratory and field studies have shown the existence of a cold stress in supercooled insects that can lead to the death of the animal before they attain their supercooling point (SCP; Turnock et al 1983Turnock et al , 1985Bale 1996). Such stress, S A , may be induced by the damage caused by cold to some structural components, such as membranes and proteins (Storey and Storey 1988 and references therein).…”

“…The freezeavoidance strategy is dependent on polyols, carbohydrates, and thermal hysteresis protein synthesis (Zachariassen 1985). The amounts of these compounds animals need to stay in a supercooled state depend on the cold intensity (T; Turnock et al 1985;Nedved et al 1998). Thus, the fitness of the freeze-avoidance strategy depends on NT (the product of the number of freezing days and cold intensity), which may be considered to be a variable describing the climatic conditions.…”

Cold hardiness of Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae) from central and southern Europe

“…A comprehensive study of interpopulation differences in cold hardiness was published by Turnock et al (1985Turnock et al ( , 1990Turnock et al ( , 1998. They compared the supercooling points (SCPs) of the pupae from six temperate populations of the freeze susceptible Delia radicum (Diptera: Anthomyidae).…”