This species’ common name is derived from the two pigmented horizontal flaps of tissue that extend across the eye to meet (but not fuse) in the center of the pupil, effectively dividing the eye into an upper and a lower portion. Modifications to the eye lens allow Anableps to see above and below the water simultaneously. This ability is enhanced by a split retina: one part receives the incoming light rays from above the water, while the other receives those that originate underwater. The Four-eyed Fish is an interesting but large and somewhat challenging species. Two other species with similar characteristics, size, and requirements are also occasionally available: A. dowei (Pacific Four-eyed Fish) from Mexico to Nicaragua; and A. microlepis (Fine-scaled Four-eyed Fish) from the Orinoco delta to the Amazon delta.
Other common names
- Striped Four-eyed Fish, Four Eyes
- Southern Mexico to northern South America (in both freshwater and brackish water).
- Males about 6in (15cm); females to 10 1/2in (27cm).
- Surface-swimming shoaler.
- Livefoods preferred, but some commercial diets accepted.
- Long covered tank only half to three- quarters full (to see the above/below-water eye orientation), moderately hard alkaline water required, with 1 teaspoonful of aquarium salt per 1 imp. gal (1 1/5 U.S.gal/4.5-5 I) added. Temperature range: 72-86F (22-30C); some deviation at either end tolerated.
- In males the anal fin is modified into a gonopodium via which sperm are transferred into the vent of the female. Eggs are fertilized internally and retained by female. She gives birth to small broods (as few as 6 offspring) of large fry about twice a year.