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 新热带食蜜蝙蝠（Neotropical nectar-feeding bats）会摄取大量糖类，并将其高能量日粮的绝大部分直接通过血液代谢利用，这提示其演化出降低体内能量储备的适应性特征。本研究针对索热尔长舌蝠（Glossophaga soricina）会省去储存能量储备所需的能量成本——即便这会使其在禁食期间面临更高易感风险这一假说展开了验证。禁食18小时的蝙蝠血糖浓度下降40%；禁食后，其胸肌与脂肪组织中的脂质、躯体脂肪酸以及肝糖原水平均出现下降。在短期禁食（即28小时）后无法维持正常血糖水平，这证实食蜜蝙蝠几乎不会储存能量储备，并表现出与该特征相关的严重禁食易感风险。本研究同时支持通用假说：针对食蜜性饮食的演化特化，会促使物种演化出降低体重的适应性特征，该特征既可减少飞行的能量消耗，又能延长觅食时长。