Mangrove rivulus
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| Rivulus marmoratus Poey, 1880 |
The mangrove killifish or mangrove rivulus, Rivulus marmoratus, is a species of fish in the Aplocheilidae family. It is endemic to the east coast of North, Central and South America, from Florida to Brazil. It is about 75 mm long.
The mangrove rivulus is a U.S. National Marine Fisheries Service Species of Concern. Species of Concern are those species about which the U.S. Government’s National Oceanic and Atmospheric Administration, National Marine Fisheries Service, has some concerns regarding status and threats, but for which insufficient information is available to indicate a need to list the species under the U.S. Endangered Species Act (ESA).
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[edit] Species Description
There is a dark spot surrounded by a yellow ring on the side of the caudal peduncle, just ahead of upper part of caudal fin base.
[edit] Ecology
The mangrove rivulus inhabits shallow, mud-bottomed ditches, bays, salt marshes and other brackish-water environments, including crab burrows. It can withstand heavy pollution of fresh or salty waters and shares its biotope with Poecilia vivipara which is much more abundant. It is usually found in water with low oxygen content.
They are either male or hermaphroditic, and females do not seem to exist. Only about 5% of a population are born as males - after three or four years about 60% of the (self-fertilizing) hermaphrodites transform into secondary males by losing their female structure and function. The proportion of males depends on the environmental temperature, below 20° C the majority are males, above 25°C all are hermaphrodites. It is the only known naturally occurring, self-fertilizing vertebrate.
Along with the ability to breed without a mate, scientists have recently discovered that it can spend up to sixty-six consecutive days out of water, which it typically spends inside fallen logs, breathing air through its skin.[1] It enters burrows inside the trees created by insects where it relaxes its territorial, aggressive behavior. During this time its gills alter so that it can retain water and nutrients, while nitrogen waste is excreted through the skin. The change is reversed once they re-enter the water.[2][3]
[edit] Conservation
This species is extremely vulnerable to habitat modification and fragmentation, environmental alteration, and human development/encroachment.
[edit] Conservation Designation
IUCN: Least Concern
American Fisheries Society: Vulnerable
Species of Greatest Conservation Need:FL
[edit] Status Reviews
Taylor (1999) is the last status review for the species.
[edit] References
- ^ "Tropical fish can live for months out of water", Reuters, Wed Nov 14, 2007 9:05pm GMT
- ^ "The fish that can survive for months in a tree", Daily Mail, 17 October, 2007
- ^ "Tropical fish can live for months out of water", Reuters, Wed Nov 14, 2007 9:05pm GMT
- Gimenez Dixon, M. 1996. Rivulus marmoratus.
- 2006 IUCN Red List of Threatened Species Downloaded on 5 August 2007.
- "Rivulus marmoratus". FishBase. Ed. Ranier Froese and Daniel Pauly. September 2007 version. N.p.: FishBase, 2007.
- NMFS. Species of Concern Fact sheet [1]
