Nilsson Göran E
Physiology Programme, Department of Molecular Biosciences, University of Oslo, PO Box 1041, N-0316 Oslo, Norway.
J Exp Biol. 2007 Jul;210(Pt 14):2403-9. doi: 10.1242/jeb.000281.
While a large respiratory surface area is good for gas exchange, it also poses several problems, including energetically unfavorable fluxes of water and ions. As a result, fishes appear to have a respiratory surface area that is matched to their oxygen demands. When faced with changes in their need for oxygen uptake, e.g. through altered physical activity or altered ambient oxygen levels, fishes have long been known to make two different adjustments: (1) to change the water flow over the gills or (2) to change the blood flow inside the gills. It has recently become clear that at least some teleosts have a third option: to reversibly remodel the gill morphology. Studies have shown that the lamellae of crucian carp Carassius carassius gills are embedded in a cell mass during normoxic conditions or at low temperature, while much of this cell mass dies off in hypoxia and at higher temperatures, thereby exposing a much larger respiratory surface area. Gill remodeling has subsequently been seen in two more cyprinids and in the mangrove killifish Kryptolebias marmoratus. In the latter case it appears to be an adaptation to periods of air exposure. Gill remodeling in response to changing respiratory requirements could be an ancient mechanism, occurring in many more teleosts than presently known. It is tempting to suggest that gill remodeling has been overlooked in many fishes, either because it is relatively subtle in some species, or because fishes are often kept at the warmer end of their temperature range where they need fully protruding lamellae.
虽然大的呼吸表面积有利于气体交换，但它也带来了几个问题，包括水和离子的能量不利通量。因此，鱼类似乎拥有与其氧气需求相匹配的呼吸表面积。长期以来，人们已知当鱼类面临氧气摄取需求的变化时，例如通过改变身体活动或改变环境氧气水平，它们会做出两种不同的调整：（1）改变鳃上的水流或（2）改变鳃内的血流。最近已经清楚的是，至少一些硬骨鱼有第三种选择：可逆地重塑鳃的形态。研究表明，在常氧条件下或低温时，鲫鱼鳃的薄片嵌入细胞团中，而在缺氧和较高温度下，大部分这种细胞团会死亡，从而暴露出大得多的呼吸表面积。随后在另外两种鲤科鱼类和弹涂鱼中也观察到了鳃重塑。在后一种情况下，它似乎是对空气暴露期的一种适应。响应不断变化的呼吸需求而进行的鳃重塑可能是一种古老的机制，在比目前已知更多的硬骨鱼中存在。很容易推测，鳃重塑在许多鱼类中被忽视了，要么是因为它在某些物种中相对不明显，要么是因为鱼类通常被饲养在其温度范围较温暖的一端，在那里它们需要完全突出的薄片。
