Supercooling points of freeze-avoiding bumble bees vary with caste and queen life stage
Supercooling points of freeze-avoiding bumble bees vary with caste and queen life stage
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避免冻结的大黄蜂的过冷点随种姓和蜂王生命阶段的不同而变化
DOI：
10.1016/j.jtherbio.2022.103196
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发表时间：
2022
影响因子：
2.7
通讯作者：
Dillon, Michael E.
中科院分区：
文献类型：
--
作者：
Keaveny, Ellen C.;Waybright, Sarah A.;Rusch, Travis W.;Dillon, Michael E.
大黄蜂在寒冷的气候中茁壮成长，包括世界各地的高纬度和高海拔地区，但大多数物种的耐寒策略在很大程度上是未知的。为了确定大黄蜂的耐寒策略，我们将大黄蜂暴露在一系列低温环境中，并测量了暴露后72小时的存活率。所有被冷冻的蜜蜂都在72小时内死亡，而只有一只蜜蜂没有被冷冻，这表明大黄蜂通常是避免被冷冻的昆虫，可能对寒冷有轻微的敏感性。然后，我们评估了引起内部结冰的温度（过冷点，SCP）在不同的大黄蜂种姓（雄蜂、工蜂和蜂王）之间，或者在不同的蜂王生命阶段、采集高度、物种或季节之间是否存在差异。雄蝶的冰冻温度明显低于工蜂或蜂王。处于越冬前或越冬状态的蜂王，其冰冻温度明显低于受二氧化碳麻醉刺激而开始卵巢发育的蜂王（即“春季”蜂王）。我们还测试了水（即湿的或干的）或斜坡速度是否会影响SCP。不出所料，接种了水的蜂王比干燥的蜂王在更高的温度下冻结。在更快的爬坡速率下（0.5°C/min vs 0.25°C/min）， SCP倾向于降低，但并不显著。我们还发现，在春秋季节采集的蜂王、在海拔差异为1100米的两个地点采集的蜂王以及三种野外捕获的大黄蜂之间，SCP没有差异。大黄蜂似乎有相对较高的、不变的scp，这可能使它们在任何季节都很容易受到寒冷的影响。由于大黄蜂不耐冻，而且似乎缺乏在远低于0°C的温度下防止冻结的能力，它们可能依赖于季节和种姓特定的微栖息地选择，在寒冷的气候中茁壮成长。
Bumble bees thrive in cold climates including high latitude and high altitude regions around the world, yet cold tolerance strategies are largely unknown for most species. To determine bumble bee cold tolerance strategy, we exposed bumble bees to a range of low temperatures and measured survival 72 h post-exposure. All bees that froze died within 72 h while only one bee died without freezing, suggesting that bumble bees are generally freeze-avoiding insects and may be slightly chill susceptible. We then assessed whether temperatures that cause internal ice formation (supercooling points, SCP) varied among bumble bee castes (drones, workers, and queens), or across queen life stages, collection elevation, species, or season. Males froze at significantly lower temperatures than workers or queens. Queens in pre-overwintering or overwintering states froze at significantly lower temperatures than queens stimulated to initiate ovary development by CO2narcosis (i.e., “spring” queens). We also tested whether the presence of water (i.e., wet or dry) or ramping rate affected SCP. As expected, queens inoculated with water froze at significantly higher temperatures than dry queens. SCP tended to be lower, but not significantly so, at faster ramping rates (0.5 °C/min vs 0.25 °C/min). We also found no differences in SCP between queen bumble bees collected in spring and fall, between queens collected at two sites differing in elevation by 1100 m, or between three field-caught bumble bee species. Bumble bees appear to have relatively high, invariable SCPs, likely making them highly susceptible to freezing across all seasons. As bumble bees are not freeze-tolerant and appear to lack the ability to prevent freezing at temperatures much below 0 °C, they may rely on season- and caste-specific micro-habitat selection to thrive in cold climates.