Mangrove Killifish

Scientists have discovered that mangrove killifish spends several months of every year living out of the water and inside trees. Living in rotten branches and trunks temporarily alter the creatures biological makeup, allowing them to breathe air. Their gills adapt to retain nutrients and water, while excreting nitrogen waste through their skin. These characteristics are reversed as soon as the creatures re-enter water life. Mangrove killifish are also the only vertebrate creature to reproduce without a mate because of their ability to develop female and male sexual organs and fertilize their eggs. Another type of fish that can breathe in air and water is the walking catfish of Southeast Asia.