|Scientific Name:||Kryptolebias marmoratus|
|Species Authority:||(Poey, 1880)|
Rivulus marmoratus Poey, 1880
|Red List Category & Criteria:||Least Concern ver 3.1|
|Reviewer(s):||Smith, K. & Darwall, W.R.T.|
|Facilitator/Compiler(s):||Hammerson, G.A. & Ormes, M.|
This species is listed as Least Concern because its extent of occurrence, number of subpopulations, and population size are large, and because the species probably is not declining fast enough to qualify for any of the threatened categories.
|Range Description:||This species is widely distributed throughout the West Indies region, from the Bahamas, including Bimini and the Andro Island (Harrington and Rivas 1958), south to northern and eastern South America to Venezuela (Taphorn 1980), including both the Greater Antilles and Lesser Antilles (Seegers 1984, Huehner et al. 1985). It also occurs along the southern half of peninsular Florida and in portions of the Florida Keys (Fowler 1928, Gilbert and Burgess 1980, Huehner et al. 1985, Taylor and Snelson 1992).
This fish was first reported in the United States from Key West (Fowler 1928, Hastings 1969). It has since been collected from several locations on both coasts of Florida on the east coast as far north as the Indian River Lagoon (Harrington and Rivas 1958, Taylor 1988. Davis et al. 1995) and near Ft. Myers (Tampa Bay) and on the west coast in mangrove and mosquito ditch habitats (Hastings 1969, Brockmann 1975, Robins et al. 1986, Taylor and Snelson 1992, Turner et al. 1992, Harrington and Rivas 1958). It is known from all east coast counties in Florida north to Brevard County, with the exception of Palm Beach County (Taylor 1993). The distribution closely parallels that of the red mangrove (Cardosoma guanhumi) with which this fish is closely associated (Davis et al. 1995).
Native:Anguilla; Antigua and Barbuda; Aruba; Bahamas; Barbados; Belize; Brazil; Cayman Islands; Cuba; Curaçao; Dominica; French Guiana; Grenada; Guadeloupe; Jamaica; Martinique; Mexico; Montserrat; Puerto Rico; Saint Kitts and Nevis; Saint Lucia; Saint Vincent and the Grenadines; Trinidad and Tobago; Turks and Caicos Islands; United States; Venezuela, Bolivarian Republic of; Virgin Islands, British; Virgin Islands, U.S.
|FAO Marine Fishing Areas:||
Atlantic – western central
|Range Map:||Click here to open the map viewer and explore range.|
This species is represented by a large number of occurrences (subpopulations) and locations (as defined by IUCN). Much of the range has not been surveyed. Field accounts are rare due to the small size and difficulty of sampling in the mangrove habitat (Taylor 1988). However, it is thought to occur at many sites throughout the rather large range (Taylor and Snelson 1992).
In 1958, there were 37 populations considered extant in the United States, all in Florida (Harrington and Rivas 1958).
Total adult population size is unknown but presumably exceeds 10,000. There are no data to indicate exactly how many individuals currently exist or have been eliminated (Taylor 1989b).
The species apparently is widely distributed and locally rare and is more common in Florida than had been previously thought. The species is apparently abundant throughout the Florida Keys, although it has been overlooked in the past due to inadequate ichthyological collecting methods (Davis et al. 1990). As many as 26 individuals have been collected from a single burrow of the great land crab (Cardosoma guanhumi) along the Indian River Lagoon (Taylor 1989a, 1990). However, most collections (based on 111 specimens collected) typically consisted of one or two individuals per burrow (Taylor 1992). Collections of greater than 140 specimens have been taken at night by several collectors at a mangrove site in Collier County, Florida (Taylor 1988). Additional specimens have been found in this habitat in south Florida and the Florida Keys (Davis et al. 1990). Fifty-one individuals were found under partially submerged logs and less frequently in leaf litter in intertidal areas of Big Mangrove Key (east of Big Pine Key), Florida; two individuals were found in identical habitats on Grand Cayman, British West Indies (Huehner et al. 1985).
Fifteen individuals were collected from a population in the Maracaibo River Basin in Venezuela (Taphorn 1980).
Populations usually consist of all female individuals. However, collections on several cays off the coast of Belize yielded 13.5–24 percent males of the 305 specimens sampled (Turner et al. 1992).
May be declining due to habitat destruction or degradation. Probably has been eliminated from areas along the lower east coast of Florida.
|Habitat and Ecology:||
Primarily coastal brackish and saltwater areas usually with low oxygen content and hard-bottom areas with silt cover (Voss et al. 1969, Loftus and Kushlan 1987, Davis et al. 1995); usually collected from mangrove or high salt marsh habitats in a salinity of 20-35 parts per thousand (Davis et al. 1990, Taylor and Snelson 1992, Taylor 1993). Also reported from freshwater where it is considered rare (Tabb and Manning 1961, Loftus and Kushlan 1987). In very shallow, stagnant water over marly muck, often associated with detritus and scant vegetation. On the east coast of Florida, often found living in burrows of the land crab Cardiosoma guanhumi, especially in beds of saltwort and glasswort; also inhabits the burrows of other crabs such as Ucides cordatus in Belize (Taylor 1989b, Davis et al. 1990). See Taylor and Snelson (1992).
Individuals are capable of leaving the water by burrowing through leaf litter (Huehner et al. 1985) and have also been observed out of the water attached to the underside of mangrove leaves. An extensive network of capillaries in the skin and fins allow absorption of oxygen when out of the water (Taylor 1989). This behaviour is probably a generalized response to environmental stress, including high concentrations of hydrogen sulphide, as well as a means of exploiting terrestrial resources (Abel et al. 1987). Eggs are able to survive for considerable periods of time out of the water in the mangrove forest substrate (Ritchie and Davis 1986). Adults are also capable of burrowing into moist mud when crab burrows dry up. They can stay buried in the mud for at least 60 days until the burrows become flooded once again by higher tides (Taylor 1989b).
Rivulus marmoratus is promising as a good estuarine bio-indicator species (to determine responses to toxins), due to its naturally inbred genetic attributes, fast growth rate, and simple husbandry (Lin and Dunson 1993, Park et al. 1994).
|Use and Trade:||Has been used in carcinogenesis testing (Metcalfe 1989).|
Habitat destruction is a significant threat. Development of coastal habitats leads to loss of mangroves and general degradation of the estuarine environment; offshore pollution events may also degrade habitat, though this species can withstand considerable water pollution. Habitat remains vulnerable to human activities, especially the impounding of high marsh habitats for mosquito control (Taylor and Snelson 1992, Davis et al 1995, Taylor et al. 1995).
The species appears to already have disappeared from impounded marsh areas in the Indian River Lagoon area in central Florida (Taylor et al. 1995). The mangrove habitat in the central Florida location has been degraded through drastic alteration of vegetation, including loss of many black mangrove trees after construction of impoundments used for mosquito control (Provost 1977). The species' existence in salt marshes is so restricted and unusual that it is constantly in peril (Taylor 1989b). At least in the northern part of the range (Indian River Lagoon, Florida), the species depends on the presence of crab burrows, and crab populations have been declining (Taylor and Snelson 1992) and are only present in non-impounded marshes (Davis et al. 1995). Areas with more habitat disturbance may exhibit greater heterozygosity. For example, there were more heterozygous individuals in a site subjected to human modifications than in a site with less disturbance (Lubinski 1993).
A population in Venezuela exhibited reduction and loss of the pelvic fins. This may have resulted from extreme inbreeding (Taphorn 1980). The conservation significance of these conditions is uncertain.
Although this fish is used extensively in bioassays and cancer research, the demand for specimens has been minimal due to the ability to easily maintain this species in the laboratory where it spawns readily (Taylor 1988).
There is a need for continued studies on life history and population dynamics (Taylor and Snelson 1992), including rates of genetic exchange among populations given hermaphroditic reproduction. Minimum viable population size needs to be determined.
There is a need to search for additional populations in southern Florida (Taylor and Snelson 1992) as well as in both impounded and particularly non-impounded high marsh habitats in central Florida (Taylor et al. 1995).
Known occurrences of both Kryptolebias marmoratus and the land crab, Cardiosoma guanhumi, should be protected. Currently there are no regulations managing the land crab; the establishment of such regulations should be encouraged (Taylor et al. 1995). Continued and stringent protection of existing intact marsh and mangrove habitats is required (Taylor 1989b). This species is a good indicator of overall health of mangrove systems due to its close association with the mangrove habitat and its high sensitivity to habitat destruction including chemical toxins (Taylor et al. 1995).
|Citation:||NatureServe 2014. Kryptolebias marmoratus. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 30 June 2015.|
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