The MHC is a group of genes that help the immune system identify microbes and parasites. They play an important role in disease resistance, as diverse genes allow animals to resist a wider range of diseases. The research published this week in the journals PLOS ONE and Immunogenetics shows that some of the genes involved in the fight against viruses, bacteria and parasites have remained the same across all crocodilian species while other immune genes seem to have diversified in crocodiles.

"The diverse environments occupied by many crocodilians, whether saltwater crocs in the Northern Territory or alligators in Florida, appear to have exposed crocodilians immune genes to a wide range of germs," Dr Gongora said.

Researchers found multiple instances of crocodilians losing and/or duplicating genes showing that their immune system is still responsive to evolutionary changes.

"We now have a genetic resource to understand the immune system in crocodilians, thanks to this research. It will enable genetic investigations of how these animals respond to local conditions including susceptibility to disease," said lead author of the article Weerachai Jaratlerdsiri, who recently completed his PhD at the University of Sydney.