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

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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.