Bartlett Jesamine C, Convey Peter, Hayward Scott A L
School of Biosciences, University of Birmingham, Edgbaston, B15 2TT, UK.
Norwegian Institute for Nature Research, Høgskoleringen 9, 7034 Trondheim, Norway.
Insects. 2020 Feb 26;11(3):147. doi: 10.3390/insects11030147.
An insect's ability to tolerate winter conditions is a critical determinant of its success. This is true for both native and invasive species, and especially so in harsh polar environments. The midge (Diptera, Chironomidae) is invasive to maritime Antarctic Signy Island, and the ability of fourth instar larvae to tolerate freezing is hypothesized to allow the species to extend its range further south. However, no detailed assessment of stress tolerance in any other life stage has yet been conducted. Here, we report that, although larvae, pupae and adults all have supercooling points (SCPs) of around -5 °C, only the larvae are freeze-tolerant, and that cold-hardiness increases with larval maturity. Eggs are freeze-avoiding and have an SCP of around -17 °C. At -3.34 °C, the CT activity thresholds of adults are close to their SCP of -5 °C, and they are likely chill-susceptible. Larvae could not withstand the anoxic conditions of ice entrapment or submergence in water beyond 28 d. The data obtained here indicate that the cold-tolerance characteristics of this invasive midge would permit it to colonize areas further south, including much of the western coast of the Antarctic Peninsula.
昆虫耐受冬季条件的能力是其生存成功与否的关键决定因素。这对于本地物种和入侵物种均适用，在恶劣的极地环境中尤其如此。蠓（双翅目，摇蚊科）入侵了南极海洋的西格尼岛，据推测，四龄幼虫的抗冻能力使该物种能够进一步向南扩展其分布范围。然而，尚未对其他任何生命阶段的应激耐受性进行详细评估。在此，我们报告称，虽然幼虫、蛹和成虫的过冷却点（SCPs）均约为-5°C，但只有幼虫具有抗冻能力，并且抗寒能力随幼虫成熟度增加。卵具有避冻能力，其SCP约为-17°C。在-3.34°C时，成虫的CT活性阈值接近其-5°C的SCP，它们可能对寒冷敏感。幼虫无法承受冰困或淹没在水中超过28天的缺氧条件。此处获得的数据表明，这种入侵蠓的耐寒特性将使其能够在更南部的地区定殖，包括南极半岛西海岸的大部分地区。
