Lyretail Swordtail Breeding Guide

Breeding the Lyretail Swordtail (Xiphophorus hellerii), a long-finned livebearer, with sexing, 24-30 day gestation, large broods, fry care and the lyretail trait.

Overview

The Lyretail Swordtail is a selectively bred strain of Xiphophorus hellerii (family Poeciliidae) with extended lyre-shaped fins. It is a livebearer with internal fertilisation. Most aquarium swordtails are hybrids to some degree because the species crossbreeds with the platy X. maculatus. Wild swordtails come from rapidly flowing, vegetated streams from Veracruz, Mexico to northwestern Honduras.

Sexing

Males develop a gonopodium and the caudal sword, absent in females; in lyretail stock the fins are elongated in both sexes. Some individuals are late-maturing males whose sword appears later, and the species can undergo female-to-male sex reversal under certain conditions.

Conditioning

An omnivore feeding on worms, crustaceans, insects and plant matter, the swordtail conditions on a varied diet in stable, slightly hard alkaline water (the species occurs across roughly 22-28 C and pH 7.0-8.0). A larger tank suits this active livebearer.

Breeding Setup

Both sexes present will breed readily. A ratio of one male to three or four females limits harassment, as males are aggressive toward each other. A well-developed male spurs female maturity and inhibits juvenile-male maturity. Note that the lyretail gonopodium is elongated, which can reduce males' fertilisation success, so breeding programmes often retain some standard-finned males.

Mating & Gestation

Males fertilise females internally via the gonopodium, and females store viable sperm for extended periods. A dark gravid spot develops near the anal fin in late pregnancy. Gestation lasts about 24 to 30 days, with maturity at roughly eight to twelve months.

Birth & Fry Care

A female produces 20 to 200 live young per brood. Dense plants give fry refuge from adults. Fry accept powdered and small live foods and grow steadily.

Common Challenges

Beyond male aggression and platy hybridisation, the lyretail trait itself complicates breeding because the lengthened gonopodium can hinder mating; keeping the line going may require pairing lyretail females with standard-finned or partially-finned males.