Least Killifish

Taxobox
name = Least Killifish

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image_caption = Least Killifish ("Heterandria formosa") female
regnum = Animalia
phylum = Chordata
classis = Actinopterygii
ordo = Cyprinodontiformes
familia = Poeciliidae
genus = "Heterandria"
species = "H. formosa"
binomial = "Heterandria formosa"
binomial_authority = Gunther, 1874

The Least Killifish, or Dwarf Livebearer, ("Heterandria formosa") is a species of livebearing fish within the family Poeciliidae. This is the same family that includes familiar aquarium fishes such as guppies and swordtails. The Least Killifish is not as commonly kept in aquaria as these species. The Least Killifish is one of the smallest fish in the world (7th smallest as of 1991)cite book|title=Baensch Aquarium Atlas|author=Baensch, H.|page=pp. 592-593|year=1991|isbn=3-88244-050-3] , and is the smallest fish found in North America.cite web|title=Occurence and Distribution of "Heterandria formosa" in Lowndes County, Georgia|url=http://findarticles.com/p/articles/mi_qa4015/is_200601/ai_n17176579|accessdate=2008-08-10]

Range and habitat

The Least Killifish is the only member of the genus "Heterandria" to be found in the United States.cite book|title=Livebearing Fishes|author=Dawes, J.|page=pp. 186-187|year=1995|isbn=0-7137-2592-3] Its range covers southeastern United States, from South Carolina south to Georgia and Florida, and through the Florida Gulf Coast to Louisiana.cite web|title=Fishbase Heterandria formosa|url=http://www.fishbase.org/Summary/SpeciesSummary.php?id=3224|accessdate=2008-08-10] It is one of the few aquarium fishes to come from North America.

The Least Killifish lives primarily in slow moving or standing freshwater but also occurs in brackish waters.

Description

The Least Killifish is one of the smallest fish and smallest vertebrates known to science. Males grow to about 2 centimeters (0.8 inches), while females grow a little larger, to about 3 centimeters (1.2 inches).cite book|title=Complete Encyclopedia of the Freshwater Aquarium|author=Dawes, J.|page=p. 276|year=2001|isbn=1-55297-544-4]

The fish is generally an olive color, with a dark horizontal stripe through the center of the body. There is also a dark spot on the dorsal fin and females also have a dark spot on their anal fin. Like most poeciliids, males' anal fins are modified into a gonopodium that is used for impregnating females during mating.

Diet

The Least Killifish primarily eats invertebrates such as worms and crustaceans. They also eat plant matter.

Breeding

Like most poeciliids, the Least Killifish is a livebearer. The male uses his modified anal fin, or gonopodium, to deliver sperm to the female. The fertilized eggs grow within the female until they hatch, and the young are released free swimming. Least Killifish have a unique breeding strategy even among livebearers. Rather than all the young being released at once, as many as 40 fry are released over a 10 to 14 day period, but occasionally over a longer period.

References