University of Göttingen, Department of Evolutionary Developmental Genetics, 37077 Göttingen, Germany
Department of Developmental Biology, Institute for Zoology, University of Cologne, 50674 Cologne, Germany.
J Exp Biol. 2019 May 20;222(Pt 10):jeb200691. doi: 10.1242/jeb.200691.
Springtails (Collembola) are ancient close relatives of the insects. The eversible vesicles are their unique paired transporting organs, which consist of an epithelium located inside a tube-like structure called the collophore on the first abdominal segment. The vesicles can be protruded out of the collophore and several lines of evidence indicate that they have a vital function in water uptake and ion balance. However, the amount of water absorbed by the vesicles and which other ions apart from Na are transported remain unknown. Using as a model, we developed protocols for two assays that enabled us to study water and ion movement across the eversible vesicles in whole living springtails. Using an inverse Ramsay assay we demonstrate that the eversible vesicles absorb water from a droplet applied onto their surface. Using the scanning ion-selective electrode technique (SIET), we show that the vesicles absorb Na and Cl from the bathing medium, secrete NH, and both absorb and secrete K H is secreted at a low level in the anterior part and absorbed at the posterior part. We did not detect transport of Ca at significant levels. The highest flux was the absorption of Cl, and the magnitude of ion fluxes was significantly lower in fully hydrated springtails. Our data demonstrate that the eversible vesicles are a transporting epithelium functioning in osmo- and ionoregulation, nitrogenous waste excretion and probably also acid-base balance.
跳虫（弹尾目）是昆虫的古老近亲。可外翻的囊泡是它们独特的成对运输器官，由位于第一腹节的管状结构 collophore 内的上皮细胞组成。囊泡可以从 collophore 中伸出，有几条证据表明它们在吸水和离子平衡方面具有重要功能。然而，囊泡吸收的水量以及除了 Na 之外还有哪些离子被运输仍然未知。我们以 作为模型，开发了两种测定法的方案，使我们能够研究整个活体跳虫中可外翻囊泡的水和离子运动。我们使用逆拉姆齐测定法证明，可外翻囊泡可以从滴在其表面的液滴中吸收水分。使用扫描离子选择性电极技术（SIET），我们表明囊泡从浴液中吸收 Na 和 Cl，分泌 NH ，并且同时吸收和分泌 K H 在前段以低水平分泌，在后段被吸收。我们没有检测到显著水平的 Ca 转运。最高的通量是 Cl 的吸收，而在完全水合的跳虫中离子通量的幅度要低得多。我们的数据表明，可外翻囊泡是一种在渗透调节和离子调节、氮废物排泄以及可能还有酸碱平衡中起作用的运输上皮。
