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.
This section covers a group of four families, in which many of the species produce live young. The family Poeciliidae contains the most popular aquarium fish that produce live young. Many beginners start with the guppy (Poecilia reticulata), progressing to swordtails such as Xiphophorus helleri. One major reason for the popularity of the group – […]
These popular fish are characterized by their breeding habits. The eggs are fertilized internally; in most species, sperm are transferred to the female via the male’s gonopodium—a tubelike projection of the anal fin—and the eggs subsequently develop in the relative safety of the female’s body.
Wrasses, 114, 115 Xenomysrus nigri (African knifefish), 97 Xenopoecilus, 56 Xiphophorus (platy), 48 Xiphophorus (swordtail), 48 Xiphophorus hdleri (swordtail), 48, 50, 51 Xiphophorus maculatus (platy), 48, 50 Xiphophorus vdriatus (platy), 48, 51 Zebrasoma flavescens (yellow tang), 113 Zebrasoma vdiferum (striped sailfin tang), 113
Mudskippers are notoriously difficult to maintain in captivity because of the demands they place on the aquarist. Species imported include Periophthalmus barbarus, Periophthalmus catonensis, and Periophthalmus kaelreukeri, but these names are often confused-and identification is uncertain.
Retail outlets tend to stock only a few brackish water fishes because people usually want either marines because of their flamboyant colours or freshwater as they are easiest. The main brackish water fishes available are Scats, Monos, Archers, Arius catfishes, Mudskippers, Anableps, and Brachygobius, plus, if you want to see them at their best, Sailfin mollies (Poecilia sp.). This last group has been dealt with in the Cyprinodonts chapter.