Alfaro cultratus

The scientific name of the species comes from the Costa Rican zoologist Anastasio Alfaro. 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. It is known as olomina in Costa Rica, as are many similar fish. == Description ==

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. Maximum recorded length of the knife livebearer is 7.5 cm for males and 8.0 cm for females. == Distribution and habitat ==

The knife livebearer is native to the Central American countries of Costa Rica, Panama and Nicaragua. but it is a powerful swimmer It is the most common poeciliid in the rivers of the Maquenque National Wildlife Refuge in Costa Rica. == Ecology ==

Alfaro cultratus is insectivorous, taking aquatic insects as juveniles and moving onto terrestrial insects in adulthood. 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. For a livebearer, the gestation period is relatively short and the brood size small. The fry reach sexual maturity within six months. == Fishkeeping ==

Alfaro cultratus is one of numerous livebearers popular in the fishkeeping hobby. It requires a temperature of to . 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. 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. == References ==