Phillips J E
Fed Proc. 1977 Oct;36(11):2480-6.
The diverse excretory systems of insects exhibit several features that appear unusual when comparisons are made with the mammalian kidney. Secretion by the Malpighian tubules of a fluid that is unlike the blood in composition, substitutes for glomerular filtration. Various reabsorptive functions, such as volume reduction, regulation of individual electrolytes, adjustment of osmotic concentration and pH regulation, which are associated with distinct renal segments in the mammalian kidney, all occur simultaneously in the rectum of terrestrial insects. Involvement of an extracellular molecular sieve in selective reabsorption is novel. As far as water transport is concerned, the rectal pads of the cockroach and locust appear to accomplish, across a single layer of cells, the same function as the countercurrent multiplier system of the mammalian kidney with its several epithelial layers. Direct absorption of water vapor in the rectum of some insects from atmospheres of low relative humidity, clearly involves quite different and unknown mechanisms. Finally, saline-water insect larvae produce hyperosmotic excreta by direct secretion of ions into the rectal lumen. They can adjust individual transport processes to form various secretions, which are appropriate to the natural waters of diverse chemical types in which these larvae thrive.
与哺乳动物的肾脏相比，昆虫多样的排泄系统呈现出一些不同寻常的特征。马氏管分泌的液体成分与血液不同，这替代了肾小球滤过作用。各种重吸收功能，如减少液体量、调节个别电解质、调整渗透压浓度以及调节pH值，这些在哺乳动物肾脏中与不同肾段相关的功能，在陆生昆虫的直肠中是同时发生的。细胞外分子筛参与选择性重吸收是很新颖的。就水的运输而言，蟑螂和蝗虫的直肠垫似乎通过单层细胞完成了与具有多层上皮细胞的哺乳动物肾脏逆流倍增系统相同的功能。一些昆虫在相对湿度较低的大气环境中，其直肠能直接吸收水蒸气，这显然涉及截然不同且未知的机制。最后，盐水环境中的昆虫幼虫通过将离子直接分泌到直肠腔中来产生高渗排泄物。它们能够调节个体运输过程以形成各种分泌物，这些分泌物适合这些幼虫所生存的不同化学类型的天然水域。
