Species: Heterandria formosa, Dwarf Livebearer, Least Killifish

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.