Data from: Metabolic recovery from drowning by insect pupae

Many terrestrial insects live in environments that flood intermittently, and some life stages may spend days underwater without access to oxygen. We tested the hypothesis that terrestrial insects with underground pupae show respiratory adaptations for surviving anoxia and subsequently reestablishing normal patterns of respiration. Pupae of Manduca sexta were experimentally immersed in water for between 0 and 13 d. All pupae survived up to 5 d of immersion regardless of whether the water was aerated or anoxic. By contrast, fifth-instar larvae survived a maximum of 4 h of immersion. There were no effects of immersion during the pupal period on adult size and morphology.
After immersion, pupae initially emitted large pulses of CO2. After a subsequent trough in CO2 emission, spiracular activity resumed and average levels of CO2 emission were then elevated for approx. 1 d in the group immersed for 1 d and for at least 2 d in the 3- and 5-d immersion treatments. Although patterns of CO2 emission were diverse, most pupae went through a period during which they emitted CO2 in a cyclic pattern with periods of 0.78 - 2.2 min. These high-frequency cycles are not predicted by the recent model of Foerster and Hetz (2010) and Grieshaber and Terblanche (2015), and we suggest several potential ways to reconcile the models with our observations. During immersion, pupae accumulated lactate, which then declined to low levels over 12 to 48 hours. Pupae in the 3- and 5-d immersion groups still had elevated rates of CO2 emission after 48 h, suggesting that they continued to spend energy on reestablishing homeostasis even after lactate had returned to low levels. Despite their status as terrestrial insects, pupae of M. sexta can withstand long periods of immersion and anoxia and can reestablish homeostasis subsequently.

许多陆生昆虫栖息于间歇性洪涝的环境中，部分生活史阶段可在无氧条件下于水下存活数日。我们针对“拥有地下蛹（underground pupae）的陆生昆虫具备应对缺氧的呼吸适应机制，并可在后续恢复正常的呼吸模式”这一假说开展了实验。我们将烟草天蛾（Manduca sexta）的蛹进行实验性浸泡（experimental immersion），浸泡时长为0至13天。无论水体是否充氧（aerated）或处于缺氧状态，所有蛹均可在最长5天的浸泡后存活。与之形成鲜明对比的是，五龄幼虫（fifth-instar larvae）的最长存活浸泡时长仅为4小时。蛹期浸泡对成虫的体型与形态无显著影响。
浸泡结束后，蛹初期会释放大量二氧化碳（CO₂）脉冲。在二氧化碳释放量出现低谷期后，气门活动（spiracular activity）恢复，且在浸泡1天的实验组中，平均二氧化碳释放量在约1天内维持在较高水平；而浸泡3天和5天的实验组，该高释放状态至少持续2天。尽管二氧化碳释放模式存在多样性，但多数蛹会经历一段以0.78至2.2分钟为周期的周期性二氧化碳释放阶段。这类高频周期无法由Foerster与Hetz（2010）以及Grieshaber与Terblanche（2015）近期提出的模型预测，我们据此提出了若干可协调该模型与实验观测结果的潜在路径。浸泡期间，蛹体内会积累乳酸（lactate），随后乳酸水平在12至48小时内回落至低水平。浸泡3天和5天的实验组蛹，在48小时后仍维持较高的二氧化碳释放速率，这表明即便乳酸已恢复至低水平，它们仍需消耗能量以重建体内稳态（homeostasis）。尽管烟草天蛾属于陆生昆虫，但其蛹可耐受长时间浸泡与缺氧环境，并可在后续恢复体内稳态。