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Least killifish (Heterandria formosa) — Poeciliidae

Least killifish

Heterandria formosa
Family: Poeciliidae
LC · Least Concern

The Least killifish (Heterandria formosa) is a brackish-water fish of the family Poeciliidae that grows up to 4 cm.

Length
3.6 cm
Water
Brackish
Diet
Omnivore
Behaviour
Small groups
Activity
Diurnal
Body shape
Torpedo-shaped
Substrate
Mixed bottom
Danger
Harmless
Range
Southeastern USA; heavily vegetated, standing to slow-flowing fresh and brackish waters.
Edibility
Not eaten

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Description

The least killifish is one of the smallest fishes in the world, a livebearing toothcarp of the family Poeciliidae from the south-eastern United States. The species grows to only about 2 to 3.5 cm; females are larger than males. It inhabits heavily vegetated, standing to slow-flowing fresh and brackish waters. Unlike most fishes the female gives birth to live young, in small numbers spread over several weeks (superfetation). As an omnivore it eats worms, small crustaceans, insects and algae. The species is popular in the aquarium. Owing to its small size it is harmless to humans.

Frequently asked questions

How do you recognise the Least killifish?

The Least killifish has a torpedo-shaped body, is mainly brown and shows a horizontal stripes pattern. One of the smallest fishes in the world; ovoviviparous, produces young at intervals (superfoetation).

Where does the Least killifish live?

The Least killifish lives in brackish water and is mostly found around mixed bottom. Southeastern USA; heavily vegetated, standing to slow-flowing fresh and brackish waters.

How big does the Least killifish get?

The Least killifish grows to a maximum of about 4 cm. On average the species is around 2 cm.

Is the Least killifish dangerous to humans?

No, the Least killifish is harmless to humans. None required: this species is harmless to humans.

Is the Least killifish edible?

The Least killifish is not usually eaten.

More photos

Least killifish (Heterandria formosa) — Poeciliidae — 2
iNaturalist ((c) Connor Gordon, some rights reserved (CC BY-NC))
Least killifish (Heterandria formosa) — Poeciliidae — 3
iNaturalist ((c) JeffreyGammon, some rights reserved (CC BY-NC))
Least killifish (Heterandria formosa) — Poeciliidae — 4
Wikimedia Commons — Brian Gratwicke (CC BY 2.0)
Least killifish (Heterandria formosa) — Poeciliidae — 5
iNaturalist ((c) Drew, some rights reserved (CC BY-NC))
Fin

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All data

Identification

English name
Least killifish verified
Scientific name
Heterandria formosa
Family
Poeciliidae
Other names
Midget Livebearer; Mosqu verified

Appearance

Size class
Small verified
Max length (cm)
3.6 verified
Average length (cm)
2.1 verified
Body shape
Torpedo-shaped sourced
Dominant colour
Brown inferred
Pattern
Horizontal stripes inferred
Tail shape
Rounded inferred
Mouth position
Superior (upward) inferred
Lips
Thin inferred
Barbels
No sourced
Dorsal fins
One continuous inferred
Dorsal spines
No sourced

Habitat & distribution

Water type
Brackish sourced
Substrate
Mixed bottom sourced
Natural range
Southeastern USA; heavily vegetated, standing to slow-flowing fresh and brackish waters. inferred
Origin
Native sourced

Behaviour & biology

Diet
Omnivore sourced
Diet (detail)
Worms, small crustaceans, insects and algae sourced
Social behaviour
Small groups inferred
Territorial
No inferred
Activity
Diurnal inferred
Reproduction
Separate sexes sourced
Sexual dimorphism
Yes inferred
Seasonality
Present year-round in its habitat; no pronounced seasonality known. inferred
Special features
One of the smallest fishes in the world; ovoviviparous, produces young at intervals (superfoetation). sourced

For anglers

Edibility
Not eaten sourced
Fishing method
Not a target species for angling; at most an incidental catch or usable as baitfish. inferred
Regulations source
FishBase ↗ inferred

Safety

Danger to humans
Harmless sourced
First aid
None required: this species is harmless to humans. sourced

Status & sources

Sources
FishBase via GBIF (DwC-A), CC-BY-NC 4.0

Same genus Heterandria

Barred livebearer (Heterandria jonesii) — Poeciliidae
Barred livebearer (Heterandria jonesii)
Poeciliidae
 Twospot livebearer (Heterandria bimaculata) — Poeciliidae
Twospot livebearer
Heterandria bimaculata
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Fin

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