Blind Cave Fish

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In an article about vestigial organs Live Science writes: “In an experiment designed by nature, the species of fish known as Astyanax mexicanus, dwelling in caves deep underground off the coast of Mexico, cannot see. The pale fish has eyes, but as it is developing in the egg, the eyes begin to degenerate, and the fish is born with a collapsed remnant of an eye covered by flap of skin. These vestigial eyes probably formed after hundreds or even thousands of years of living in total darkness. As for the experiment, a control is needed; and luckily for us, fish of the same species live right above, near the surface, where there is plenty of light, and these fish have fully functioning eyes. To test if the eyes of the blind A. mexicanus could function if given the right environment, scientists removed the lens from the eye of the surface-dwelling fish and implanted it into the eye of the blind fish. It was observed that within eight days an eye started to develop beneath the skin, and after two months the fish had developed a large functioning eye with a pupil, cornea, and iris. The fish were blind, but now they see.”

Live Science

Editorial Comment: In the totally dark environment of the caves the developing fish do not get the right stimulus for the eyes to properly develop, even though the genes for eyes are there. In fact, it seems to be the darkness that turns the eye genes off. When they get the right signals, via tissue taken from a fish that developed in light conditions, the eyes develop.

The remnants of the eyes in the adult cave fish could be called vestigial, but this is nothing to do with evolution. As the intelligent scientists who designed the experiment have noted, fish of the same species that develop and live in lighted conditions do have eyes. Therefore, the incompletely formed eyes of the cave fish are a loss of function brought about by an unusual environment, and provide no evidence for how eyes came to exist. Again they are change without evolution.

For more details of the experiment described by Live Science see ScienceNOW 12 Oct 2004 and Nature 13 Oct 2004. We suspect you will probably conclude with us that this experiment designed by human scientists, (not an imaginary goddess called “nature”) provides evidence that embryonic development in fish shows that genes alone do not determine results. Correct gene expression involves the interaction of genes with the right environment to produce the right results. (Ref. vestigial, embryology, ichthyology)

Evidence News, 7 October 2009