Tardigrades are microscopic organisms, famous for their tolerance against extreme environments. The establishment of rearing systems of multiple species has allowed for comparison of tardigrade physiology, in particular in embryogenesis. Interestingly, in-lab cultures of limnic species showed smaller variation in hatching timing than terrestrial species, suggesting a hatching regulation mechanism acquired by adaptation to their habitat. To this end, we screened for coordinated gene expression during the development of two species of tardigrades, Hypsibius exemplaris and Ramazzottius varieornatus, and observed induction of the arthropod molting pathway. Exposure of ecdysteroids and juvenile hormone analog affected egg hatching but not embryonic development in only the limnic H. exemplaris. These observations suggest a hatching regulation mechanism by the molting pathway in H. exemplaris.

中文翻译：

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两种不同孵化协调的缓步动物转录组的比较。

缓步动物是微生物，以其对极端环境的耐受性而闻名。多个物种饲养系统的建立可以对缓步动物的生理学进行比较，特别是在胚胎发生方面。有趣的是，湖沼物种的实验室培养物在孵化时间上的变化比陆地物种更小，这表明其孵化调节机制是通过适应其栖息地而获得的。为此，我们筛选了两种缓步动物（Hypsibius exemplaris 和 Ramazzottius varieornatus）发育过程中的协调基因表达，并观察了节肢动物蜕皮途径的诱导。暴露于蜕皮类固醇和保幼激素类似物会影响卵的孵化，但不会影响仅在湖沼 H. exemplaris 中的胚胎发育。这些观察结果表明 H. exemplaris 的蜕皮途径存在孵化调节机制。