Freeze tolerance in larvae of the winter-active Diamesa mendotae Muttkowski (Diptera: Chironomidae): a contrast to adult strategy for survival at low temperatures

Abstract

The winter-active Diamesa mendotae Muttkowski (Diptera: Chironomidae) is freeze intolerant in the adult stage with a low mean supercooling point (SCP) of $)20°C. However, cold-hardiness strategies for immatures of this species are unknown. In this study, we measured SCP values for D. mendotae larvae, pupae and adults using surface-contact thermometry. In addition, the lower lethal temperature (LLT) was determined for the larval stage. The mean SCPs for larvae ()7.4°C) and pupae ()9.1°C) were relatively high compared to adults ()19.7°C). Our results indicate that the larvae of D. mendotae are freeze tolerant with a LLT 99 ()25.4°C), $)10°C lower than their minimum SCP ()15.6°C). Freeze tolerance in these larvae may be a strategy to provide protection from short-term exposures to ice crystals or to permit diapause within frozen substrates. The change in cold-hardiness strategy from freeze tolerant to freeze intolerant between the larval and adult stages of this species is likely a result of the different habitats occupied by these two life stages.

Thermotolerance and heat shock response in the cold-stenothermal chironomid (NE Italy)

“…According to Bouchard et al (2006), one-and two-way analyses of variance on the arcsine-square-root-transformed proportion of survival were performed to test for significant differences in survival among temperature treatments (Statistica 8.0, StatSoft Inc, USA). When significant differences were found (p<0.05), Tukey's post-hoc test was used to separate the means.…”

A case study of Heleomyzidae (Diptera) recorded on snow in Poland with a review of their winter activity in Europe

“…Adults of Scoliocentra nigrinervis had the second lowest supercooling point of snow-active insects studied (mean -16.5°C, range -20.5/-13°C) (Sømme & Østbye, 1969). The lowest supercooling point was reported for the chironomid Diamesa mendotae Muttkowski (-21.6°C) (Bouchard et al, 2006). It is noteworthy that some fl ies can survive even long, severe and snowy winters as immature stages: for example, larvae of Heleomyza borealis, a snow-active fl y especially widely distributed in the Arctic, can survive temperatures as low as -60°C and need a lower than -15°C temperature stimulus and thereafter warmer period to pupate (Block, 2002).…”

An invitation to measure insect cold tolerance: Methods, approaches, and workflow

“…An alternative approach is to expose groups of insects to a pre- determined set of temperatures (e.g. at 5 °C intervals; Bouchard et al, 2006;Kleynhans et al, 2014). This approach has advantages in design and execution; in particular, it can allow random assignment of insects to treatments, allow all of the exposures to be made on a single day, and is more suitable for using longer-term measures of survival.…”