Heterandria formosa

least killifish






Type Locality

“Mobile, Alabama; New Orleans, Louisiana; and Gulf States” (Agassiz 1855).


Etymology/Derivation of Scientific Name







Maximum size: 36 mm TL (Page and Burr 1991).


Coloration: Dark bands on sides with vertical bars; large black spots near bases of caudal fins of both sexes and on anal fin of females (Hubbs et al. 2008).




Body shape: Dorsal fin origin slightly behind anal fin origin (Hubbs et al. 2008).


External morphology:


Internal morphology: Intestinal canal short with few convolutions (Hubbs et al. 2008).


Distribution (Native and Introduced)

U.S. distribution: This coastal species ranges from North Carolina through Florida and west to the Texas border (Hubbs et al. 2008).


Texas distribution: Collected only on the west bank of the Sabine River near the Interstate Highway 10 crossing in Orange County (Hanks and McCoid 1988; Hubbs et al. 2008).


Abundance/Conservation status (Federal, State, NGO)

Currently Stable (Warren et al. 2000) in the southern United States.


Habitat Associations

Macrohabitat: Inhabits coastal and peninsular areas (Martin 1980).


Mesohabitat: Weedy pond and stream margins, from fresh to brackish (about 30 ppt.) water (Martin 1980).



Spawning season:


Spawning habitat:


Spawning Behavior:




Age at maturation




Growth and Population structure: 




Food habits:


Phylogeny and morphologically similar fishes

Tribe Heterandriini (Martin 1980).


Host Records



Commercial or Environmental Importance





Agassiz, L. 1855. Remarks on Dr. B. Dowler’s paper “Discovery of viviparous fish in Louisiana.” American Journal of Science and Arts [Ser. 2] 19(55):133-136.


Fraser, E.A., and R.M. Renton. 1940. Observation on the breeding and development of the viviparous fish, Heterandria formosa. Quart. J. Micros. Sci. 81:479-520.


Hanks, B.G., and M.J. McCoid. 1988. First record for the least killifish, Heterandria formosa (Pisces: Poeciliidae), in Texas. Texas Journal of Science 40:447-448.


Hubbs, C., R.J. Edwards, and G.P. Garrett. 2008. An annotated checklist of the freshwater fishes of Texas, with keys to identification of species. Texas Journal of Science, Supplement, 2nd edition 43(4):1-87.

Martin, F.D. 1980. Heterandria formosa (Aggasiz), Least killifish.  pp. 547 in D. S. Lee et al., Atlas of North American Freshwater Fishes. N. C. State Mus. Nat. Hist., Raleigh, i-r+854 pp.


Page, L. M. & B. M. Burr.  1991.  A field guide to freshwater fishes of North America north of Mexico.  Houghton Mifflin Company, Boston, Massachusetts. 432 pp.


Reimer, R.D. 1970. A food study of Heterandria formosa Agassiz. Am. Midl. Nat. 83(1):311-315.


Rosen, D.E, and R.M. Bailey. 1963. The poeciliid fishes (Cyprinodontiformes): their structure, zoogeography, and systematics. Bull. Am. Mus. Nat. Hist. 126:1-176.


Scrimshaw, N.S. 1944a. Superfetation in poeciliid fishes. Copeia 1944(3):180-183.


Scrimshaw, N.S. 1944b. Embryonic growth in the viviparous poeciliid, Heterandria formosa. Biol. Bull. 87:37-52.


Scrimshaw, N.S. 1945. Embryonic development in poeciliid fishes. Biol. Bull. 88:233-246.


Scrimshaw, N.S. 1946. Egg size in poeciliid fishes. Copeia 1946(1):20-23.


Seal, W.P. 1911. Breeding habits of the viviparous fishes Gambusia holbrooki and Heterandria formosa. Proc. Biol. Soc. Wash. 24:91-96.


Turner, C.L. 1937. Reproductive cycles and superfetation in poeciliid fishes. Biol. Bull. 72:145-164.


Warren, M.L., Jr., B.M. Burr, S.J. Walsh, H.L. Bart, Jr., R.C. Cashner, D.A. Etnier, B.J. Freeman, B.R. Kuhajda, R.L. Mayden, H.W. Robison, S.T. Ross, and W.C. Starnes. 2000. Diversity, Distribution, and Conservation status of the native freshwater fishes of the southern United States. Fisheries 25(10):7-29.