PHYSIOLOGICAL REGULATION OF IONIC IN AMUR IDE (LEUCISCUS WALECKII) DURING THEIR SPAWNING MIGRATION

Dali Nor lake, one of the four lakes in Inner Mongolia Autonomous Region, China, is a typical saline-alkaline lake with high concentrations of carbonate salts (alkalinity up to 60 mmol/L, pH 9.6 and salinity 6‰). Amur ide (Leuciscus waleckii) is one of the only two existing economic fish in the Dali Nor Lake with the character of spawning migration. To investigate the osmotic and ionic regulation mechanism of the L. waleckii during spawning migration form Dali Nor lake to Gongger river, we analyzed serum ionic (Na⁺, K⁺, Cl⁻, Ca²⁺ and Mg²⁺) and hormone (PRL, GH and IGF-1) levels, Na⁺/K⁺-ATPase activities in gills, intestinal and kidney, Ca²⁺/Mg²⁺-ATPase activities in gills and structure of gills in L. waleckii collected form Dali Nor lake and Gongger river. In addition, above parameters were studied in L. waleckii during 24-h transfer from lake to river water. Compared to lake fish, river fish had decreased Na⁺, significantly increased Cl⁻ in serum as well as significantly increased Na⁺/K⁺-ATPase activities in kidney and intestinal while no significant change in gills. There were no significant differences of K⁺, Ca²⁺, Mg²⁺ and hormone (GH, IGF-1 and PRL) levels in serum between lake and river fishes. During 24-h lake-to-river water transfer, Cl⁻ increased and K⁺ decreased significantly in serum, Na⁺/K⁺-ATPase activities in gills, intestinal and kidney and Ca²⁺/Mg²⁺-ATPase activi-ties in gills, as well as PRL and IGF-1 levels all increased significantly (P<0.05). Histology of gills showed that mucous cell counts were significantly higher in lake fish compared to that of river fish, while branchial chloride cells (CCs) counts have no obvious difference between lake and river fish, but the size of branchial CCs on filaments slightly increased in river fish. It is concluded that L. waleckii could maintain high serum ionic levels though endocrine control of Na⁺, K⁺-ATPase in osmotic regulatory tissues during spawning migration form Dali Nor lake to Gongger river.