Simulated winter warming negatively impacts survival of Antarctica's only endemic insect

Antarctic winters are challenging for terrestrial invertebrates, and species that
live there have specialised adaptations to conserve energy and protect against
cold injury in the winter. However, rapidly occurring climate change in these
regions will increase the unpredictability of winter conditions, and there is
currently a dearth of knowledge on how the highly adapted invertebrates of
Antarctica will respond to changes in winter temperatures.
2. We evaluated the response of larvae of the Antarctic midge, Belgica antarctica,
to simulated winters at three ecologically relevant mean temperature scenarios:
warm (−1°C), normal (−3°C) and cold (−5°C). Within each scenario, larvae were
placed into three distinct habitat types in which they are commonly observed
(decaying organic matter, living moss, and Prasiola crispa algae). Following the
simulated overwintering period, a range of physiological outcomes were measured,
namely survival, locomotor activity, tissue damage, energy store levels and
molecular stress responses.
3. Survival, energy stores and locomotor activity were significantly lower following
the Warm overwintering environment than at lower temperatures, but tissue
damage and heat shock protein expression (a proxy for protein damage) did not
significantly differ between the three temperatures. Survival was also significantly
lower in larvae overwintered in Prasiola crispa algae, although the underlying
mechanism is unclear. Heat shock proteins were expressed least in larvae
overwintering in living moss, suggesting it is less stressful to overwinter in this
substrate, perhaps due to a more defined structure affording less direct contact
with ice.
4. Our results demonstrate that a realistic 2°C increase in winter microhabitat temperature
reduces survival and causes energy deficits that have implications for subsequent
development and reproduction. While our Warm winter scenario was close tothe range of observed overwintering temperatures for this species, warmer winters
are expected to become more common in response to climate change. Conversely,
if climate change reduces the length of winter, some of the negative consequences
of winter warming may be attenuated, so it will be important to consider this factor
in future studies. Nonetheless, our results indicate that winter warming could
negatively impact cold-adapted insects such as the Antarctic midge.

南极冬季对陆生无脊椎动物而言极具挑战，栖息于此的物种已演化出特化适应策略，以在冬季保存能量并抵御低温损伤。然而，这些区域正快速发生的气候变化正加剧冬季环境条件的不可预测性，目前学界对南极高度特化的无脊椎动物如何响应冬季温度变化的认知仍存在空白。
2. 本研究针对南极摇蚊（Belgica antarctica）的幼虫，在三种符合生态相关性的平均温度情景下开展了模拟冬季实验：暖温组（-1℃）、常温组（-3℃）与低温组（-5℃）。在每个温度情景中，幼虫被置于三种其野外常见的生境类型中：腐烂有机质、活苔藓以及卷曲扁藻（Prasiola crispa）。模拟越冬期结束后，研究人员对一系列生理指标进行了测定，具体包括存活率、运动活性、组织损伤程度、能量储备水平以及分子应激响应。
3. 相较于低温环境，暖温越冬组的存活率、能量储备与运动活性均显著降低，但组织损伤程度与热休克蛋白（heat shock protein）的表达水平（可作为蛋白质损伤的替代指标）在三种温度组间无显著差异。在卷曲扁藻（Prasiola crispa）中越冬的幼虫存活率同样显著偏低，尽管其背后的分子机制尚未明确。在活苔藓生境中越冬的幼虫，热休克蛋白的表达水平最低，这表明该生境的越冬压力更小，可能是因为其结构更为规整，减少了幼虫与冰体的直接接触。
4. 本研究结果表明，冬季微生境温度实际升高2℃会降低幼虫存活率并引发能量不足，这将对后续的发育与繁殖产生不利影响。尽管本次实验的暖温冬季情景接近该物种野外越冬温度的实测范围，但在气候变化的影响下，暖冬事件的发生频率预计将进一步升高。反之，如果气候变化缩短了冬季时长，冬季变暖带来的部分负面影响可能会得到缓解，因此在未来的研究中纳入该因素至关重要。综上，本研究结果显示，冬季变暖可能会对南极摇蚊这类冷适应型昆虫产生负面冲击。