The structure of the pronephros and development of mesonephric kidney in Russian sturgeon larvae, Acipenser gueldenstaedtii Brandt at different stages of early postembryonic development (from hatching to 14 days), were studied with histological and electronic microscopy methods. The larval pronephros is represented by the system of bilaterally located pronephric tubules with ciliated nephrostomes and funnels and exogenous single glomus, which is not integrated directly into pronephric tubules and located in the pronephric chamber. The glomus is positioned below the dorsal aorta and vascularized by its capillaries. The glomus has the same features of the thin structure that are typical of and necessary for the function of a filtering organ. The structure of the pronephros in acipenserids is discussed and compared with teleosts and amphibians. Histogenesis of the mesonephric kidney is observed during the period of pronephros functioning; it is complete by the time the larvae transfer to exogenous feeding. At this moment, the pronephros undergoes significant structural degradation.

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