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

牛鲨和锯鳐是世界上著名的热带大河湖泊栖息动物，尤以赞比西河闻名。然而，很明显它们为什么会去淡水地区。该研究的目的是阐明非洲东南部淡水板蝗的分类学、适应性和保护。在大约35年前牛鲨出没的赞比西河、林波波河和卢西亚湖，我们没有收集到牛鲨和锯鳐。在南非和莫桑比克的沿海城镇，可以看到锯鳐的长鼻超过1米，但渔民最近没有捕捉到任何锯鳐。我们可以得到信息，赞比西河的鲨鱼和锯鳐非常多，另一方面，牛鲨和锯鳐是在马达加斯加的贝齐博卡河采集的。虽然Kiener（1963）曾在马达加斯加短暂地报道过它们的出现，但它们的标本并没有保存在博物馆里。我们从马达加斯加把牛鲨和锯鳐带到了日本，并保存在科学博物馆里。我们将这些标本的发生和描述投稿给国际科学期刊。从这些依拉斯莫科树枝上取下的一块材料用作分析。牛鲨的Sr / Ca比值高于锯鳐。这表明牛鲨最近才进入淡水地区。结果表明，淡水板鳃锯鳐的肌肉中含有大量的牛磺酸、尿素、次牛磺酸样物质、肌球蛋白、β-丙氨酸、甘糖碱和氧化三甲胺，肝脏中含有大量的牛磺酸和尿素。这表明这些物质具有渗透剂的作用。

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.