Mangrove Rivulus

Description

Mangrove rivulus are small and slender fish that are dark brown to green in color with speckles of orange and black. They are amphibious fish, meaning they can survive on land and in water. Their small, rounded fins propel them through the water and their tail fin helps them to flip on land. Mangrove rivulus are tiny, reaching just 1 to 2.5 inches (2.5 to 6 centimeters) in length.

Range

These fish are found in the United States throughout the Caribbean and along both coasts of central South Florida. Not surprisingly, mangrove rivulus are usually found in mangrove forests, particularly in stagnant pools. They take refuge in moist land crab burrows, leaf litter, logs, and even coconuts during dry spells or when water conditions become unfavorable. They can survive for two months out of water. The primary predators of mangrove rivulus are birds and mangrove water snakes.

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.

Life History

These fish 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. The exact lifespan of the mangrove rivulus is unknown, but they have lived for eight years in captivity.

Conservation

Mangrove rivulus in Florida are listed under the Endangered Species Act as a species of concern. Their main threats are their vulnerability to habitat degradation and alteration, as well as pollution. They are relatively abundant in the Caribbean.

Fun Fact

To survive on land and in water, mangrove rivulus are able to breathe through their skin and their gills.

Sources

Florida Museum of Natural History

Journal of Experimental Biology

Mangrove.org

National Geographic

National Marine Fisheries Service, National Oceanic and Atmospheric Administration

NatureServe Explorer

The IUCN Red List of Threatened Species

The Society for Integrative & Comparative Biology