Mbanga Blandine, van Dyk Cobus, Maina John N
Department of Zoology, University of Johannesburg, Auckland Park Campus 2006, Kingsway, Johannesburg, South Africa.
Department of Zoology, University of Johannesburg, Auckland Park Campus 2006, Kingsway, Johannesburg, South Africa.
Zoology (Jena). 2018 Oct;130:6-18. doi: 10.1016/j.zool.2018.07.005. Epub 2018 Jul 23.
The respiratory organs of the African sharptooth catfish, Clarias gariepinus, were studied to broaden existing understanding of the adaptive stratagems that have evolved for air-breathing in fish. The gills were well-developed and the air-breathing organs (ABOs) comprised labyrinthine organs (LOs), suprabranchial chamber membranes (SBCMs) and gill fans (GFns). Respectively, the gills and the LOs had the highest mass-specific respiratory surface areas of 133.7 and 141.9 mm per gram and among the ABOs, with a harmonic mean thickness of the blood-barrier (BGB) of 0.39 μm, the LOs had the thinnest BGB followed by the GFns (0.48 μm) and the SBCMs (0.49 μm): the water-blood barrier of the gills was relatively much thicker (7.93 μm). Vindicating why C. gariepinus is an obligate air-breather, the total mass-specific morphometric (anatomical) diffusing capacity of the ABOs for O per unit body weight (W) (Dto/W) comprised 90.5% of the mean total value for all the respiratory organs. Compared with the East African catfish, Clarias mossambicus, the Dto/W of the ABOs of C. gariepinus was 5.7 times greater. The difference between the two species of fish may be explained by the physicochemical differences of the aquatic habitats they occupy: the former occupies a seasonal river which dries up during the summer months leaving shallow pools of water in which the O concentrations are very low and CO very high while the later populates a highly eutrophic dam where the O levels greatly fluctuate seasonally.
对非洲尖齿胡鲶（Clarias gariepinus）的呼吸器官进行了研究，以拓展对鱼类为适应空气呼吸而进化出的适应性策略的现有认识。鳃发育良好，空气呼吸器官（ABO）包括迷路器官（LO）、鳃上腔膜（SBCM）和鳃扇（GFn）。鳃和迷路器官的质量比呼吸表面积最高，分别为每克133.7和141.9平方毫米，在空气呼吸器官中，血屏障（BGB）的调和平均厚度为0.39微米，迷路器官的血屏障最薄，其次是鳃扇（0.48微米）和鳃上腔膜（0.49微米）：鳃的水-血屏障相对厚得多（7.93微米）。这就解释了为什么加氏胡鲶是专性空气呼吸者，空气呼吸器官每单位体重（W）对氧气的总质量比形态测量（解剖学）扩散能力（Dto/W）占所有呼吸器官平均总值的90.5%。与东非鲶鱼（Clarias mossambicus）相比，加氏胡鲶空气呼吸器官的Dto/W大5.7倍。这两种鱼之间的差异可能由它们所占据的水生生境的物理化学差异来解释：前者占据一条季节性河流，在夏季干涸，留下浅水池，其中氧气浓度非常低，二氧化碳浓度非常高，而后者生活在一个富营养化程度很高的水坝中，那里的氧气水平季节性波动很大。
