Cave Fish and Selection?

Science Daily has an article about a nifty bit of research concerning blindness in cave fish. As is well know, fish living in caves loose their eyesight and eventually their eyes. The question the research was designed to answer was whether this loss was due to natural selection or genetic drift.


Researchers examined:

…the genetic basis of regressive evolution in the eyes and pigmentation of Mexican cavefish. To do so, they mapped the quantitative trait loci (QTL) determining differences in eye and lens sizes as well as the melanophore–or pigment cell–number between cave and surface fish. These QTL represent genes where new mutations arose in cave populations. To better understand the genetic basis for regressive evolution, they focused on two alternative explanations for regression: natural selection, in which beneficial DNA mutations become more common over time, and genetic drift, in which the frequencies of these mutations can rise or fall over time due solely to statistical variation.

The results were interesting. Mutations that affected eye or lens size were caused by selection evolved via the effects of natural selection. Mutations that affected pigmentation seemed to evolve via drift. So, what is happening is that the eye in the cavefish are being changed by two of the forces of evolution. Cool!
The research is being published in Current Biology

3 Responses

  1. When I was in college, the rationale for cave fish eye degeneration was “conservation of energy.” It seems that “evo-devo” has been making progress in biospeleology since that time.
    There have been a number of articles appearing in Science mentioning evolution of blind cave fish. Some reported on meetings, at least 1 a research article:
    Yamamoto, Y., & Jeffery, W.R., 2000, Central role for the lens in cave fish eye degeneration: Science 289(5479):631-633.
    They found the lens must form properly in order for the rest of the eye to develop. Another report from a 2000 meeting of the Society for Developmental Biology suggested soome blind cave fish may have gained more/more robust teeth and taste buds at the expense of sight due to a change in expression of a key facial-development gene (Vogel, 2000, Science 288(5474):2119-2120). A similar meeting report is noted from 2002 (Pennisi, 2002, Science 298(5595):953-955).

  2. Mutations that affected eye or lens size were caused by selection
    Selection can’t cause mutations. I’m assuming you (they?) meant mutations that affect eye/lens size are under selection.

  3. RPM – no, that was just haste and bad writing on my part. Good catch, I have corrected it.

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