Scientific Name: Kryptolebias marmoratus
Description: Mangrove rivulus are small, slender, dark brown to green in color with speckles of orange and black. They are amphibious fish, meaning that they can survive on land as well as in water. Their small, rounded fins propel them through the water and their tail fin helps them to flip on land.
Size: Mangrove rivulus are tiny, just 1 to 2.5 inches in length.
Diet: Mangrove rivulus eat smaller fish, crabs, insects, snails, and worms. They can capture insects on land and bring them back to the water to eat.
Predation: The primary predators of mangrove rivulus are birds and mangrove water snakes.
Typical Lifespan: The exact lifespan of the mangrove rivulus is unknown, but they have lived for 8 years in captivity.
Habitat: Unsurprisingly, mangrove rivulus are usually found in mangrove forests, particularly in stagnant pools. They take refuge in moist land crab burrows, leaf litter, logs, even coconuts during dry spells or when water conditions become unfavorable. They can survive for two months out of water—quite a remarkable feat for a fish!
Range: Mangrove rivulus are found throughout the Caribbean and along both coasts of south/central Florida.
Life History and Reproduction: As if their amphibious tendencies weren’t enough, mangrove rivulus are fascinating for another reason. They are the only known example of a self-fertilizing hermaphroditic vertebrate. In other words, many individuals have both male and female reproductive parts and are capable of producing genetically identical copies of themselves. Sexual reproduction also takes place, though, because under certain conditions, male rivulus do exist. In the presence of males, hermaphrodites function as females.
Fun Fact: To survive on land and in water, mangrove rivulus are able to breathe through their skin and their gills.
Conservation Status: Mangrove rivulus in Florida are listed as a Species of Concern by the State of Florida and the U.S. National Marine Fisheries Service due to vulnerability to habitat degradation and alteration, development and mosquito control impoundment construction. They are relatively abundant in the Caribbean.