Ramsay J A
Philos Trans R Soc Lond B Biol Sci. 1976 May 13;274(932):203-26. doi: 10.1098/rstb.1976.0043.
In the so-called "cryptonephric" condition of the excretory system in insects the distal ends of the Malpighian tubules are closely applied to the rectum and enclosed with it in a special chamber, the perinephric space, separated from the rest of the body cavity by the perinephric membrane. The term "rectal complex" refers to this association of tubules and rectum, which is found in the larvae (but not in the adults) of most Lepidoptera. In the mealworm (Coleoptera) the rectal complex has notable ability to remove water from the faeces, but this ability is not conspicuously developed in the larvae of the two species of Lepidoptera here studied: Pieris brassicae and Manduca sexta. On the other hand these larvae have notable ability to maintain salt balance under heavy dietary loading, and in this the rectal complex plays an important part. A study of salt balance in more detail has shown that more sodium can be eliminated in the faeces than enters the rectal complex from the intestine. Consideration of other possible routes of entry points strongly to the Malpighian tubules. Superimposed upon a new flow of tubule fluid out of the rectal complex there is a tidal flow, brought about by the rectal musculature and amplified by dilatations of the cryptonephric tubules, which could bring in fluid from the free tubules and afford opportunity for the uptake of salts. Evidence is presented in support of this view. This tidal flow of tubule fluid and uptake of salts could be the basis of the build-up of high osmolarity in the perinephric fluid and could contribute to the removal of water from the faeces. It could also be the basic mechanism in the mealworm, the leptophragmal mechanism being superimposed upon it.
在昆虫排泄系统所谓的“隐肾”状态下，马氏管的远端紧密贴附于直肠，并与之一起被包裹在一个特殊的腔室——围肾间隙中，围肾间隙通过围肾膜与体腔的其余部分分隔开来。术语“直肠复合体”指的是这种小管与直肠的关联，在大多数鳞翅目昆虫的幼虫（但成虫中不存在）中可以发现。在黄粉虫（鞘翅目）中，直肠复合体具有从粪便中去除水分的显著能力，但在所研究的两种鳞翅目昆虫——粉纹夜蛾和烟草天蛾的幼虫中，这种能力并不明显。另一方面，这些幼虫在高负荷饮食下具有显著的维持盐分平衡的能力，在这方面直肠复合体起着重要作用。对盐分平衡的更详细研究表明，粪便中排出的钠比从肠道进入直肠复合体的钠更多。考虑其他可能的进入途径后，强烈表明钠来自马氏管。在从小管复合体流出的新的小管液流之上叠加着一种潮汐流，这是由直肠肌肉组织引起的，并通过隐肾小管的扩张而放大，它可以从游离的小管中引入液体，并为盐分的吸收提供机会。文中提供了支持这一观点的证据。这种小管液的潮汐流和盐分的吸收可能是围肾液中高渗透压形成的基础，并且有助于从粪便中去除水分。它也可能是黄粉虫中的基本机制，而薄片机制则叠加在其上。
