Tetrapods and fish have adapted distinct carbamoyl-phosphate synthase (CPS) enzymes to initiate the ornithine urea cycle during the detoxification of nitrogenous wastes. We report evidence that in the ureotelic subgenus of extremophile fish Oreochromis Alcolapia, CPS III has undergone convergent evolution and adapted its substrate affinity to ammonia, which is typical of terrestrial vertebrate CPS I. Unusually, unlike in other vertebrates, the expression of CPS III in Alcolapia is localized to the skeletal muscle and is activated in the myogenic lineage during early embryonic development with expression remaining in mature fish. We propose that adaptation in Alcolapia included both convergent evolution of CPS function to that of terrestrial vertebrates, as well as changes in development mechanisms redirecting CPS III gene expression to the skeletal muscle.

四足动物和鱼类已经适应了独特的氨基甲酰磷酸合酶（CPS）酶，以在含氮废物排毒过程中启动鸟氨酸尿素循环。我们报告的证据表明，在极端嗜水鱼类Oreochromis Alcolapia的尿道亚属中，CPS III经历了会聚性进化并使其对氨的适应性得以适应，这是陆生脊椎动物CPS I的典型特征。与其他脊椎动物不同，CPS III的表达异常Alcolapia定位于骨骼肌，并在早期胚胎发育过程中在成肌谱系中被激活，而表达仍保留在成熟鱼中。我们建议在Alcolapia中进行适应包括CPS功能向陆生脊椎动物的趋同进化，以及将CPS III基因表达重定向至骨骼肌的发育机制的变化。