Transport Across Insect Excretory Epithelia
Transport Across Insect Excretory Epithelia
复制标题
通过昆虫排泄上皮的运输
DOI：
10.1007/978-3-642-46364-8_8
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发表时间：
1978
期刊：
影响因子：
--
通讯作者：
S. Maddrell
中科院分区：
文献类型：
--
作者：
S. Maddrell
One of the most remarkable features of insects is their ability to flourish in environments characterized by extreme osmoregulatory stress. They can live in fresh water, in deserts, in extremely hypersaline fluids or in waters of very unbalanced ionic content. They can do all this in spite of their very small size, which accentuates the problem by increasing the ratio of their surface area to volume. Part of this ability is due to the low permeability of their external cuticle and part to the relatively large volume of their extracellular fluids, which reduces the effects of ion and water movements into or out of the animal. The excretory system, however, is of paramount importance in that its activity ultimately controls the composition of the internal environment of the animal. It should not surprise us, therefore, to find that it can do some remarkable things. For example, in blood-sucking insects it can eliminate fluid at a rate equivalent to removing 5-10 percent of the extracellular fluid in one minute; while at the other extreme it can take up water vapour from air of a relative humidity of only 45 percent. Other cases are known where, for example, parts of the system secrete fluid containing 3 mol 1-1 KCI or 2 mol 1-1 MgS04 or 1.0 mol 1-1 NH4Clor 150 mmoll-1 nicotine. A point that needs to be stressed at the outset is that the transport systems which control the composition of the internal environment are not confined to one organ, so that in dealing with the insect excretory system one has in fact to refer to activities of salivary glands, Malpighian tubules, the midgut, the anterior hindgut, the rectum and the anal papillae. Indeed, virtually all insect epithelia which separate the internal environment from the external environment, or such inward extensions of it as the alimentary canal, are involved in excretory activity. By excretory activity is meant those processes which lead to an effective removal from the metabolically active parts of the body of substances which would otherwise interfere with metabolism (MADDRELL, 1971 a). Until relatively recently, research on transport in insect excretory systems has been properly focussed on those processes which are of central importance. Thus much early research was concerned with the way in which the primary excretory fluid is generated (a process analogous to glomerular filtration in vertebrates) and with the subsequent reabsorption of the useful parts of it, particularly water. Recently, however, there have been discovered a variety of other excretory transport processes in insects, and the reader will find that
