Low energy reserves are associated with fasting susceptibility in Neotropical nectar bats Glossophaga soricina

Abstract Neotropical nectar-feeding bats consume large amounts of sugar and use most of their energy-rich diet directly from the bloodstream, suggesting an adaptation towards lower body energy reserves. Here we tested the hypothesis that bats Glossophaga soricina spare the energy costs of storing energy reserves, even if this would represent a risky susceptibility during fasting. Blood glucose concentrations in 18 h fasted bats showed a 40% decrease. Breast muscle and adipose tissue lipids, as well as carcass fatty acids and liver glycogen, were also decreased following fasting. The inability to keep normoglycemia following a short-term fasting (i.e. 28 h) confirm that nectar bats invest little on storing energy reserves and show a severe fasting susceptibility associated to this pattern. Our study also support the general hypothesis that evolutionary specializations towards nectar diets involve adaptations to allow a decreased body mass, which reduces the energy costs of flight while increases foraging time.

摘要：新热带区食花蜜蝙蝠会摄取大量糖类，并将多数高能量日粮直接用于血液供能，这提示它们演化出了体能量储备较低的适应策略。本研究检验了如下假说：索诺拉长舌蝠（Glossophaga soricina）会省去储存能量储备所需的能量消耗，即便这会使其在禁食期间面临更高的易感风险。对禁食18小时的蝙蝠进行血糖浓度检测后发现，其血糖水平下降了40%。禁食后，蝙蝠的胸肌与脂肪组织脂质、躯体脂肪酸以及肝糖原含量均出现下降。在短期禁食（即28小时）后无法维持正常血糖水平，这证实了食花蜜蝙蝠几乎不会储存能量储备，且呈现出与该特征相关的严重禁食易感倾向。本研究同时支持这一通用假说：针对食花蜜饮食的进化特化涉及体重降低的适应机制，该机制可降低飞行的能量消耗，同时延长觅食时长。