Alfaro cultratus, the knife livebearer, is a species of tropical freshwater fish from the family Poeciliidae. It hails from Central America and is often kept in home aquaria.
Alfaro cultratus | |
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Scientific classification ![]() | |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Cyprinodontiformes |
Family: | Poeciliidae |
Genus: | Alfaro |
Species: | A. cultratus |
Binomial name | |
Alfaro cultratus (Regan, 1908) | |
Synonyms[1] | |
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The scientific name of the species comes from the Costa Rican zoologist Anastasio Alfaro.[1] The vernacular name for Alfaro cultratus, knife livebearer, comes from the two knife-shaped rows of scales near the tail on the lower end of the fish.[2] It is known as olomina in Costa Rica,[3] as are many similar fish.[4]
It has two knife-shaped rows of scales on the lower edge of its caudal peduncle. Its body is overall olive-gray, paler on the belly, while the flanks have blueish or green hues. The fins are transparent, but the caudal fin develops a dark edging as the fish ages.[2] Maximum recorded length of the knife livebearer is 7.5 cm for males and 8.0 cm for females.[1]
The knife livebearer is native to the Central American countries of Costa Rica, Panama and Nicaragua.[1] It is usually found in small groups in slow to moderately fast flowing creeks and ditches and in the shorelines of large rivers,[5] but it is a powerful swimmer[2] and has also been recorded inhabiting a fast flowing stream in a rainforest.[6]
It is the most common poeciliid in the rivers of the Maquenque National Wildlife Refuge in Costa Rica.[3]
Alfaro cultratus is insectivorous, taking aquatic insects as juveniles and moving onto terrestrial insects in adulthood.[5]
Like most American poeciliids, the knife livebearers reproduce ovoviviparously. After a gestation period of 24 days, the female gives birth to 10 to 30 young, seldom more.[1] For a livebearer, the gestation period is relatively short and the brood size small.[2] The fry reach sexual maturity within six months.[1]
Alfaro cultratus is one of numerous livebearers popular in the fishkeeping hobby. It requires a temperature of 24 °C (75 °F) to 28 °C (82 °F). The fish is intolerant of stagnant water, being susceptible to bacterial infections, making it necessary to change about 30% of the aquarium water twice a month. Aquatic plants help reduce its natural skittishness.[2]
The knife livebearers are best kept in a single species aquarium. The adults should be fed small live food such as daphnia, but will also take flake food. The fry can be fed brine shrimp nauplii.[2]
Taxon identifiers |
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