Dwarf Livebearer

Dwarf Livebearer
Dwarf Livebearer
Adult female
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cyprinodontiformes
Family: Poeciliidae
Genus: Heterandria
Species: H. formosa
Binomial name
Heterandria formosa
Gunther, 1874[verification needed]

The Dwarf Livebearer or Least Killifish (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 Dwarf Livebearer is not as commonly kept in aquaria as these species. The Dwarf Livebearer is one of the smallest fish in the world (7th smallest as of 1991),[1] and is the smallest fish found in North America.[2] Despite the common name "Least Killifish", it belongs to the family Poeciliidae and not to one of the killifish families.


Range and habitat

The Dwarf Livebearer is the only member of the genus Heterandria to be found in the United States.[3] Its range covers southeastern United States, from South Carolina south to Georgia and Florida, and through the Florida Gulf Coast to Louisiana.[3][4] It is one of the few aquarium fishes to come from North America.

The Dwarf Livebearer lives primarily in slow moving or standing freshwater but also occurs in brackish waters.[4]


The Dwarf Livebearer is one of the smallest fish and smallest vertebrates known to science.[3] Males grow to about 2 centimeters (0.8 inches), while females grow a little larger, to about 3 centimeters (1.2 inches).[3][5]

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.


The Dwarf Livebearer primarily eats invertebrates such as worms and crustaceans.[4] They also eat plant matter.[4]


Like most poeciliids, the Dwarf Livebearer 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. Dwarf Livebearer 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.[1][3][5]


  1. ^ a b Baensch, H. (1991). Baensch Aquarium Atlas. pp. 592–593. ISBN 3-88244-050-3. 
  2. ^ "Occurrence and Distribution of Heterandria formosa in Lowndes County, Georgia". Georgia Journal of Science. 2006. http://findarticles.com/p/articles/mi_qa4015/is_200601/ai_n17176579. Retrieved 2008-08-10. 
  3. ^ a b c d e Dawes, J. (1995). Livebearing Fishes. pp. 186–187. ISBN 0-7137-2592-3. 
  4. ^ a b c d "Fishbase Heterandria formosa". http://www.fishbase.org/Summary/SpeciesSummary.php?id=3224. Retrieved 2008-08-10. 
  5. ^ a b Dawes, J. (2001). Complete Encyclopedia of the Freshwater Aquarium. p. 276. ISBN 1-55297-544-4. 

External links

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