[Rodlet cells of fish in calcium deficiency in the external environment].

The ultrastructure of rodlet cells from the heat kidney of the carp Cyprinus carpio L. and tilapia Oreochromis mossambicus Peters has been studied. All the investigated cells displayed a common structure. The number of rodlet cells increased after exposure of fishes in Ca(2+)-free water or in the water supplemented with NH4+ or Cd2+. The latter were found to suppress Ca(2+)-absorption from the environment.