The researchers found that both the cave and river forms of the tetras displayed identical behaviors during reproduction. In order to continue observations during the dark hours, they recorded the fish using infrared cameras. To test their hypothesis, the scientists set up separate laboratory aquaria for captured river and cave tetras, exposed them to 12 hr light-dark cycles, and observed the fishes’ mating rituals. Conversely, if they mated during dark hours then it would suggest a ‘pre-evolutionary’ trait that may have advantaged their shared ancestor in colonizing cave environments. The team hypothesized that if the river tetras (seeing form) mated during daylight hours then it is likely that the ability to carry out full mating rituals in the dark must have evolved in the cave tetras (blind form) in response to the environmental conditions. The objective of the experiment was to observe the breeding behavior of both forms under identical light conditions. The team designed a clever experiment using the Mexican tetra ( Astyanax mexicanus Figure 1) which has two distinct forms: river dwelling (which can see) and cave dwelling (which are blind). By Clinton & Charles Robertson from RAF Lakenheath, UK & San Marcos, TX, USA & UK -– Mexican Tetra (Astyanax mexicanus) Uploaded by Jacopo Werther, CC BY 2.0, The two forms of the Mexican tetra, the river dwelling form with functional vision (top) and the blind cave dwelling form (bottom). Gender : No distinguishing external differences between the sexes.Figure 1. Will grow large eventually needing bigger tankīlind Cave Tetra Tank Mates : Tropicals and some cichlidsĭiet / Fish Food : Omnivore, will accept flakes, granules, pellets, frozen foods and live foods. May nip at tank mates.Īquarium Size : Minimum 30 litres for just a school of 6. Temperament / Behavior : Fairly peaceful, keep them in schools of 6 or more. The results have scientists hopeful that there is a treatment to cure blindness in humans.īlind Cave Tetra Mexican Tetra / Blind Cave TetraĬommon Names : Blind Cave Tetra, Mexican Tetra Many strides in the science of the eye have been reached because of research conducted on this fish. These fish are being used in studies about eye growth and transplants. They may nip at tank mates when first introduced into a new aquarium, but once they learn that they are not food – they rarely do it again. They accept all types of food in the aquarium trade.Īlthough they are blind, they very rarely swim into the tank sides, decor or other tank mates. These are avid, keen feeders not shy at feeding times. A sand or small gravel substrate is preferred. They prefer subdued lighting, as it is closer to their natural habitat. There is no need for eye sight in the pitch black caves, so they have evolved to adapt to these conditions.īlind Cave Tetras can reach up to 4 inches. They range from Texas to Mexico, with the sighted version from Mexico to Panama. The Blind Cave Tetra lives in deep caves in the wild. They are pink, but will get an iridescent sheen to them as they get older. These cave tetras are also completely devoid of pigmentation. There is a form that has eyes, although you do not generally see this version on the market. They are born with eyes as fry, but the eyes degenerate and are reabsorbed back into the body at a few weeks old. These guys make terrific subjects for a tropical setup.Īs their name would indicate, the Blind Cave Tetras have no eyes. One of the toughest fish in the industry is surprisingly the Blind Cave Tetra.
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