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Species: Heterandria formosa, Dwarf Livebearer, Least Killifish

All Families:   All Genera:   All Species:

black stripe along body; black blotch front of D
teeth compressed
male: pelvic tips not swollen, pectoral 5th ray not scalloped
male sex organ - no fleshy palp, down-curved hook at tip



Heterandria formosa Girard, 1859

Least Killifish, Dwarf Livebearer

Head and body moderately slender to moderately robust, moderately compressed at rear, upper profile slightly convex; head depressed; snout blunt, shorter than eye; front nostril not tubular; covering of eye not continuous with skin of head; mouth very small, opens at front, oblique, lower jaw slightly projecting, top jaw protractile; jaw teeth consist of an outer row of large compressed teeth, and 2 inner rows of small pointed teeth; 1 dorsal fin with short base, at rear of body, 6-8 rays, origin well behind anal fin in male, over mid-anal in female; anal fin 6-10 rays; pelvic origin well behind pectoral base, near anal fin, tip of fin same in both sexes; pectorals high on flank; male without swollen pelvic tips and pectoral 5th ray not scalloped; 3rd anal ray unbranched; anal fin modified in male to form an elongate sex organ, tip of that organ curved slightly downwards, with a down-curved hook at end, no fleshy palp; tail base relatively narrow; tail fin rounded; scales smooth and relatively large; 27-29 on side.

Color brownish olive above; flank with 6-9 indistinct darker bars, a thick black stripe from mouth to tail base; a black spot the size of 1 scale at end of stripe; dorsal fin of both sexes and anal fin of female with a large black spot at base; dorsal fin of both sexes with outer edge red.

Size: to 3.9 cm (females much larger than males).

Fresh to brackish waters.

Depth range: 0-1 m.

South Carolina to E Texas.

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  • Brackish
  • Freshwater
  • Non Marine
  • Inshore
  • Inshore Only
Water Column Position
  • Bottom
  • Estuary
  • Freshwater
FishBase Habitat
  • Demersal
Feeding Group
  • Carnivore
  • Data
  • Omnivore
  • Planktivore
  • Data
  • Zooplankton
  • Benthic microalgae
  • Mobile benthic worms
Egg Type
  • Data
  • Live birth
  • No pelagic larva
  • No pelagic phase
Global Endemism
  • All species
  • Greater Caribbean endemic
  • West Atlantic Endemic
Regional Endemism
  • Continent
  • Continent only
  • GC endemic
  • All species
  • Resident
Climate Zone
  • Subtropical (23-35N, Florida / Carolinas / Bermuda)
IUCN Red List
  • Least concern
  • Listed
  • Not listed
Length Max
  • 3.9
Depth Range Min
  • 0
Depth Range Max
  • 1