Latest update November 13th, 2024 1:00 AM
The Four-eyed Fish
The four-eyed fish are a genus, Anableps, of fishes in the family Anablepidae. They have eyes raised above the top of the head and divided in two different parts, so that they can see below and above the water surface at the same time.
Like their relatives, the one-sided livebearers, four eyed fishes only mate on one side, right-”handed” males with left-”handed” females and vice versa.
Livebearers are fish that retain the eggs inside the body and give birth to live, free-swimming young.
The eggs are retained inside the body of the female for protection but they are essentially independent of the mother and she does not provide them with any nutrients.
In contrast, fish such as splitfins and halfbeaks are viviparous, with the eggs receiving food from the maternal blood supply through structures analogous to the placenta of placental mammals.
Four-eyed fish inhabitat freshwater and brackishwater and are only rarely coastal marine. They originate from lowlands in southern Mexico to Honduras and northern South America.
These fish spend most of their time at the surface of the water. Their diet mostly consists of terrestrial insects which are readily available at the surface, however, they may consume other foods such as other invertebrates, diatoms, and small fishes.
Four-eyed fish in their habitat
These fish will group differently depending on the species. A. anableps commonly congegrates in schools. A. microlepis also is gregarious, but restricts its schools to about a dozen individuals; it is also recorded to be found singly or as couples. A. anableps is also known for the ability to survive out of water exposed to air, such as during low tide.
The maximum length of these species is up to 32 cm TL in A. microlepis, making this species the largest in the order Cyprinidontiformes.
These fish are one-sided livebearers and their reproductive organs are unique to its subfamily. This characteristic is only shared with the related genus Jenynsia.
The four-eyed fishes only have two eyes each, but the eyes are specially adapted for their surface-dwelling lifestyle.
The eyes are positioned on the top of the head, and the fish floats at the water surface with only the lower half of each eye underwater. The two halves are divided by a band of tissue and the eye has two pupils, connected by part of the iris.
The upper half of the eye is adapted for vision in air, the lower half for vision in water. The lens of the eye also changes in thickness top to bottom to account for the difference in the refractive indices of air versus water.
The Four-Eyed Fish Anableps anableps, is truly an amazing creature. The pupil in each eye is horizontally divided into two parts, allowing it to be able to see clearly below and above the water.
This adaptation allows this fish to find food at or below the surface and also gives it extra protection against predators. Since it spends virtually all of its life swimming at the surface, it needs this extra protection.
They are a schooling fish so they will do best if kept in groups of six or more. The Four-Eyed Fish are also a brackish fish. Other brackish fish such as Archer Fish, Mudskippers or Mollies are known to make good aquarium fish mates.
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