Mangrove rivulus are small tropical fish up to 75 mm in length found in swamps from Florida to Brazil. The fish is not very attractive in appearance - this is due to the fact that it is able to survive on land for two months and reproduce in a very strange way.
All representatives of the species are hermaphrodites (although several purely males have been found): these are the only vertebrates in the world with the ability to self-fertilize.
In 2007, researchers found that this fish can live on land for up to 66 days in a row, living inside the moist cavities of rotting mangrove logs, and sometimes even in old beer cans or coconut shells. During the day, mangrove rivulus transform their gills in such a way as to gain the ability to breathe through the skin.
Moreover, fish are able to travel over land with the help of their tails, which push off the ground in order to make a powerful jump - this allows rivulus to leave an unfavorable aquatic environment with a low concentration of oxygen or a high content of hydrogen sulfide - a compound that is toxic to fish. The ability to move on land by jumping also allows the fish to escape predators and hunt ground prey such as crickets.