Coutchié P A, Machin J
Am J Physiol. 1984 Aug;247(2 Pt 2):R230-6. doi: 10.1152/ajpregu.1984.247.2.R230.
Water vapor absorption is compared in the two tenebrionid larvae Tenebrio molitor and Onymacris marginipennis. Thresholds for absorption and "absorption capacity," which depend on ion transport by Malpighian tubules, are consistently different over the entire size range of the two species. Because of lower thresholds, uptake rates of Onymacris are over double those of Tenebrio in larvae of the same size at identical ambient water activities. By contrast, passive determinants of uptake, rectal conductance, and morphometry are similarly scaled with size in the two species. A ventilatory mechanism of vapor entry into the rectum is proposed for both species, since the anal canal is too long and narrow for exclusively diffusional entry. Vapor uptake in relation to larval mass was described by a simple diffusion model through rectal tissue, where flux varied directly with surface area and inversely with the distance between the lumen and Malpighian tubules. Failure of rectal conductance to increase proportionally with body mass means that size-specific vapor uptake declines with larval size in both species.
比较了两种拟步甲幼虫黄粉虫和边缘胸鳖甲对水蒸气的吸收情况。吸收阈值和“吸收能力”取决于马氏管的离子运输，在这两个物种的整个大小范围内，它们始终存在差异。由于阈值较低，在相同环境水活度下，相同大小的边缘胸鳖甲幼虫的吸收速率是黄粉虫的两倍多。相比之下，吸收的被动决定因素、直肠传导率和形态测量在这两个物种中与大小的比例相似。由于肛管过长且过窄，无法仅通过扩散进入，因此推测这两个物种都有一个使水蒸气进入直肠的通气机制。通过直肠组织的简单扩散模型描述了与幼虫质量相关的水蒸气吸收情况，其中通量与表面积成正比，与管腔和马氏管之间的距离成反比。直肠传导率未能与体重成比例增加，这意味着这两个物种中特定大小的水蒸气吸收量会随着幼虫大小的增加而下降。
