Nucleolar Organizer Region (NOR) Polymorphism in Some Indian Anuran Amphibian

The amphibians are the first vertebrate class to colonize the terrestrial environment from the aquatic environment, originating from Crossopterygian fishes in the late Devonian period. They have been the subject of various investigations because of their position in the phylogenetic history, morphological peculiarity, low diploid chromosome number with elongated metaphase chromosome and controversial nature of sex determination. The Indian subcontinent is rich in amphibian fauna. Still, the cytogenetical studies, particularly the karyomorphological study about the distribution of constitutive heterochromatin and nucleolar organizer region (NOR), need to be more detailed. The present book chapter has, therefore, been oriented to describe Amphibia's biology briefly. In addition, cytogenetics of Amphibia with particular reference to constitutive heterochromatin distribution and nucleolar organizer region polymorphism in some Indian anurans such as bufonids, ranids and rhacophorids were written.