Sastemtics, Adaptability, and Conservation of Freshwater Elasmoranchs in Scutheast Africa

众所周知，牛鲨和锯鱼生活在世界各地的热带大河大湖中，特别是在赞比西河。然而，它们为什么会去淡水区是很清楚的。这项研究的目的是阐明东南部非洲淡水弹涂鱼的系统学、适应性和保护。我们无法从赞比西河、林波波河和卢西亚湖采集到牛鲨和锯鱼，这些地方大约35年前就出现了牛鲨。在南非和莫桑比克的沿海小镇，展示了长达1米的锯鱼嘴，但渔民最近没有捕到任何锯鱼。我们可以得到的信息是赞比西河的鲨鱼和锯鱼非常稀有。另一方面，牛鲨和锯鱼是从马达加斯加的Betsiboka河采集的。虽然Kiener(1963)曾简要报道过这些产于马达加斯加的板鱼，但它们的标本并未保存在博物馆。我们将牛鲨和锯鱼从马达加斯加带到日本，并将它们保存在科学博物馆。我们向国际科学期刊投稿了这些标本的发生和描述。从这些弹性支链中提取的一块材料用作分析。牛鲨的锶钙比高于锯鱼。这表明牛鲨是最近才进入淡水区的。结果表明，锯鱼肌肉中含有大量的牛磺酸、尿素、次牛磺酸类物质、肌球蛋白、β-丙氨酸、甘氨酸甜菜碱和TMAO，肝脏中含有大量的牛磺酸和尿素。这表明这些物质起着渗透剂的作用。

Bull shark and sawfish are known to inhabit tropical big rivers and lakes in the world, especially famous in Zambezi River. However, it is a clear why they go up to the freshwater area. The purpose of the research throws light on systematics, adaptability and conservationo freshwater elasmobranches in southeast Africa. We could not collect Bull shark and sawfish from Zambezi River, Limpopo River and Lakes Lucia where bull shark occurred about 35years ago. In coastal town of South Africa and Mozambique, snout of sawfish longer than 1 meter on display, but fisherman does not catch any sawfish recently. We could get information that sharks and sawfish in Zambezi River are very ra On the other hand, bull shark and sawfish were collected from Betsiboka River, Madagascar. Although occurrence of these elasmobrancke from Madagascar was reported briefly by Kiener (1963), their specimens were not kept in museum We carried bull shark and sawfish from Madagascar to Japan and kept them in scientific museum. We contribute occurrence and description of these specimens to intemation scientific journal. A piece of materials from these elasmobranches uses as analyses. The ratio of Sr to Ca in bull shark is higher than that sawfish. This shows that bull shark go into freshwater area quite recently. As a result on the analysis of extractive nitrogenous compourd from freshwater elasmobranches, sawfish kept plenty of taurine, urea, hypotaurine-like substance, sarcocin, (β-Alanin, glycinbetaine an TMAO in their muscle, and plenty of taurine and urea in their liver. This suggested these substances function as a osmolite.