Approx Max Length : 12cm

Onesided Livebearer - Jenynsia lineata Fish Profile & Care Guide

The Onesided Livebearer is a rare gem in the aquarium hobby. It has captivated only a select few dedicated hobbyists. With its strikingly attractive greenish-orange body adorned with dark, broken horizontal stripes, this fish is quite unique. While not commonly kept, it thrives when provided with a few basic care requirements, making it a unique and fascinating addition to any aquarium.

The Onesided Livebearer, a peaceful and social species, thrives in groups. In captivity, they exhibit shoaling behaviour, preferring to stay in groups, which provides them with a sense of security and encourages natural behaviours. This peaceful nature makes them a reassuring choice for any aquarist. Keeping a group of at least six individuals is recommended to boost their well-being.

When selecting tankmates for Onesided Livebearers, it's important to choose other peaceful species that share similar environmental requirements. Suitable companions include small livebearers like Guppies and Platies and non-aggressive Tetras and Rasboras. Additionally, bottom-dwelling species such as Corydoras catfish can coexist harmoniously with this fish. Avoid housing them with larger, aggressive fish that may exhibit predatory behaviour or cause stress. Providing a well-planted aquarium with ample hiding spots will further enhance the compatibility and comfort of all tank inhabitants.

The Onesided Livebearer is a versatile species that can adapt to various water conditions, including freshwater and brackish environments. This adaptability empowers aquarists to create a suitable environment for these fish, ensuring their health and longevity in captivity. Providing a well-planted tank with ample swimming space and hiding spots will mimic their natural habitat and promote natural behaviours. Regular water changes and proper filtration are essential to maintain water quality, especially if keeping them in brackish conditions.

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Sexual Dimorphism

The Onesided Livebearer exhibits notable sexual dimorphism. Females are generally larger, reaching up to 12 centimetres in length, while males typically grow to about 4 centimetres. A distinctive feature in males is the development of a gonopodium, a specialized tubular copulatory organ formed by modifications of the anal fin rays, which facilitates internal fertilization.

Quick Facts

Scientific Name	Jenynsia lineata
Year Described	1842
Kingdom	Animalia
Classification	Actinopterygii
Order	Cyprinodontiformes
Family	Anablepidae
Genus	Jenynsia
Origins	Brazil Argentina Uruguay
Approx Max Size	12 cm
Temperament	Peaceful
Aquarium Level	Middle - Top
Difficulty	Beginner - Intermediate
Shoaling	Yes
Best kept as	Groups 6+
Diet & Feeding	Omnivore
Reproduction	Livebearer
Average Lifespan	Up to 3 Years

Water Parameters

Water Type	Freshwater/Brackish
pH	7.0 - 8.0
GH	10 - 20

Ideal Temperature Range
℉	64 – 77
℃	18 – 25

Natural Habitat

The Onesided Livebearer is endemic to Argentina, Uruguay, and Brazil in South America. It is commonly found in rivers and lagoons within coastal Basins, inhabiting freshwater and brackish water environments ranging from temperate-cold to temperate-warm climates. Remarkably, this species has occasionally lived in seawater along coastlines and tide pools among rocks, thriving in areas with abundant algal growth.

Breeding

The Onesided Livebearer is a viviparous species, giving birth to live young rather than laying eggs. The gestation period typically lasts around six weeks, culminating in the birth of 10 to 20 fry, though instances of up to 40 offspring have been documented.

Notably, the Onesided Livebearer exhibits a unique reproductive morphology where the female's genital opening is asymmetrical. This anatomical feature has led to the species being termed "onesided livebearers." Some sources suggest that mating occurs between individuals with complementary genital orientations, with right-sided males pairing with left-sided females and vice versa. However, this claim is debatable, as other studies have not observed such strict lateralized mating patterns.

Providing a well-maintained environment with stable water and ample vegetation in captivity can encourage breeding. Separating the fry from adult fish post-birth is advisable to prevent predation and ensure higher survival rates.

Diet & Feeding

The Onesided Livebearer is an omnivorous species with a diet that includes insects and epibenthic cyanophytes. In captivity, they will happily accept a variety of foods, including high-quality flake foods, live or frozen brine shrimp, daphnia, and bloodworms. Providing a balanced diet that incorporates both plant-based and protein-rich foods is essential for their health and vitality. Regularly offering blanched spinach or spirulina-based vegetables can help meet their herbivorous dietary needs.

It's important to note that Onesided Livebearers may graze on algae in the aquarium, contributing to their overall dietary intake. However, relying solely on natural algae growth is insufficient; supplemental feeding is necessary to ensure they receive adequate nutrition. Maintaining a consistent feeding schedule, offering small portions multiple times daily, and monitoring their consumption will help prevent overfeeding and maintain water quality.