[Anatomo-histologic findings clarifying the phylogenetic relationships between salmonoid fish (Salmonoidei)]

The comparative anatomo-histological analysis of the medial gut of Osmeridae and Plecoglossidae after Iwai (1962) has revealed a great similarity in the structure of this entosomatic organ suggesting their phylogenetically close nature. On the contrary, the fine structure of the medial gut in these two families substantially differs from the structure of this organ in Salmonoidee. Pronounced distinctions were found between the structure of the medial gut of smelts and that of the pike (Esox lucius Linné). The complicatedly differentiated medial gut of the pike is so different from the primitive gut of modern smelts that the hypothesis (Starks, 1930; Berg, 1940) on the origin of Ecosoidei from ancient Osmeridae does not seem probable. The data obtained by the anatomo-histological analysis in combination with data of other sciences should be taken into consideration when creating the natural system of Salmonoidei, since they contribute to more exact character of their phylogenetic relations.