Data from: The cutaneous lipid composition of bat wing and tail membranes: a case of convergent evolution with birds

The water vapor permeability barrier of mammals and birds resides in the stratum corneum (SC), the outermost layer of the epidermis. The molar ratio and molecular arrangement of lipid classes in the SC determine the integrity of this barrier. Increased chain length and polarity of ceramides, the most abundant lipid class in mammalian SC, contributes to tighter packing and thus to reduced cutaneous evaporative water loss (CEWL). However, tighter lipid packing also causes low SC hydration, making it brittle; whereas high hydration softens the skin at the cost of increasing CEWL. Cerebrosides are not present in the mammalian SC; their pathological accumulation occurs in Gaucher’s disease, which leads to a dramatic increase in CEWL. However, cerebrosides occur normally in the SC of birds. We tested the hypothesis that cerebrosides are also present in the SC of bats, since they are likely necessary to confer pliability to the skin, a quality needed for flight. We examined the SC lipid composition of four sympatric bat species and found that, as in birds, their SC has substantial cerebroside contents, not associated with a pathological state, indicating convergent evolution between bats and birds.哺乳动物与鸟类的水蒸气渗透屏障定位于表皮最外层的角质层（stratum corneum, SC）。SC内脂质类的摩尔比与分子排布决定了该屏障的完整性。作为哺乳动物SC中含量最丰富的脂质类，神经酰胺（ceramides）的碳链长度增加与极性增强有助于脂质更紧密地堆砌，从而降低皮肤蒸发失水（cutaneous evaporative water loss, CEWL）。但过度紧密的脂质堆砌同时会降低SC的水合程度，使皮肤变脆；而高水合状态虽能软化皮肤，却会以增加CEWL为代价。哺乳动物SC中不存在脑苷脂（cerebrosides），脑苷脂的病理性积累会引发戈谢病（Gaucher’s disease），并导致CEWL大幅升高。但鸟类的SC中正常存在脑苷脂。鉴于蝙蝠飞行需要皮肤具备柔韧性，而此类脂质或为赋予该特性所必需，我们验证了“蝙蝠SC中亦存在脑苷脂”这一假说。我们对4种同域分布蝙蝠物种的SC脂质组成进行了检测，结果发现与鸟类一致，其SC中含有大量脑苷脂且未伴随病理状态，这表明蝙蝠与鸟类之间存在趋同演化。