Vaterite otoliths in some freshwater fishes of the Lower Friuli Plain (NE Italy)

Otoliths of different species of freshwater fishes from the Lower Friuli Pl ain were analysed. In all the fishes, one out of the three otoliths (asteri scus) is composed by vaterite. Previous research argued for some kind of ge netic control on the occurrence of different modifications in otoliths alth ough the environmental influence is not clear. We suppose that a different organic matrix influences the growth of different calcium carbonate modific ations in each otolith of freshwater fishes and that the environment could furnish a surplus of carbonate causing the different polymorphs.