Brain morphology in Acipenser stellatus and Acipenser persicus

Sturgeons as the precious commercial fishes have co-evolved a number of adaptations to their habitat and lifestyle. The relationship between brain morphology and behavioral ecology has been confirmed in many chondrichthyes and teleost fish species. However, very little is known on the central nervous systems of sturgeon species. In this research, the relative brain size (encephalization) and the relative development of four brain areas in two sturgeons are investigated. Two integration areas (the telencephalon and the metencephalon or corpus cerebellum) and two sensory brain areas (mesencephalon and myelencephalon which receive primary projections from eye and octavolateralis senses, respectively) are examined. The analysis of brain size reveals that the integration area is developed more that the sensory area. The volume of cerebellum is significantly large in theses species, comprising up to two third of the total volume of brain. This is different from brain development of most teleost and chondrichthyes species, which have large mesencephalon and telencephalon, respectively. This study suggests that sturgeons have evolved different sensory strategies to cope with the demands of life in the depth of the sea.