Bony fish · Cyprinodontiformes · Poeciliidae

Green Swordtail

Xiphophorus hellerii

Least Concern

The species is abundant and widely distributed; it faces no significant short-term risk. See full glossary

The swordtail, a livebearing fish of the rivers of Mexico, Guatemala and Honduras, in which the male sports a sword-shaped extension on the lower edge of the tail fin. It is omnivorous and lives in clear, well-oxygenated streams. It is one of the most widespread aquarium fish in the world.

Size

8 cm – 16 cm

Diet

Omnivore

Combines animal and plant food depending on availability.

Activity

Diurnal

Active mainly during the day.

Social structure

Colony

Lives in large concentrations, often for breeding reasons.

Sighting difficulty

Easy

FreshwaterOmnivore Diurnal Colonial Fish Freshwater

17countries4same family

Fun facts

It does not lay eggs: the female retains the embryos and gives birth to fully formed young that can swim straight away.
The sword on the tail is no use for swimming: it is a sexual ornament, and the classic experiments with this fish showed that females prefer the males with the longest sword.
Escapes and releases by aquarists have established it as an exotic species in rivers on every continent except Antarctica.
It is a livebearer: the female gives birth to fully formed, free-swimming young, with no free egg stage.
The sword-shaped tail belongs to the male alone, and it is a classic case in the study of sexual selection: females prefer it long even though it imposes a swimming cost on its bearer.
Females can store sperm and produce several successive broods from a single mating.
It has been introduced into numerous countries through aquarium releases and figures among the exotic species established on several islands and river basins.

Life cycle & biology

Skeleton type: Vertebrate - internal bony skeleton (fish)
Habitat & environment: Fast-flowing streams, springs and rivers of Central America
Sexual maturity: 10 months
Gestation / incubation: 4-6 weeks of internal gestation

Sources consulted: https://es.wikipedia.org/wiki/Xiphophorus_hellerii