Unique and ancestral features in trunk kidney microanatomy and ultrastructure of omul Coregonus migratorius

This study presents novel data on the microanatomy and ultrastructure of the omul Coregonus migratorius trunk kidney. Adult individuals of C. migratorius were sampled in the Barguzin Bay of Lake Baikal. Active leuko‐ and erythropoiesis were found in the interstitium of the mesonephros. For the first time, cells with radially arranged vesicles have been described in the renal interstitium of C. migratorius. The quantitative characteristics of blood cells and ultrastructural parameters of leukocytes reflected the functioning of the non‐specific defence system in the organism. The share of the renal interstitium, morphological diversity of the epithelial cells of the nephron tubules, the ultrastructural features of the renal corpuscles and nephron tubules and the number of mitochondria in leukocytes and ion‐transporting cells were typical for representatives of the whitefish Coregonus lavaretus complex and thus considered ancestral features of the present‐day C. migratorius population reflecting its adaptive potential to living in an ultra‐deep Lake Baikal.