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    Enhanced prey capture skills in Astyanax cavefish larvae are independent from eye loss
    (Springer Nature, 2014-10-03) Espinasa, Luis; Bibliowicz, Jonathan; Jeffery, William R; Rétaux, Sylvie
    Enhanced food-finding efficiency is an obvious adaptive response to cave environments. Here, we have compared the food-finding abilities of Astyanax surface fish and blind cavefish young larvae in their first month of life, in the dark. Our results show that enhanced prey capture skills of cavefish are already in effect in fry soon after the yolk is depleted and the young larvae must find food for themselves. Moreover, using prey capture competition assays on surface fish fry with lensectomies, we showed that eye-dependent developmental processes are not the main determinant for enhanced prey capture skills. Finally, using F2 hybrid larvae resulting from crosses between surface fish and cavefish, we found that reduced eyes do not confer a selective advantage for prey capture by fry in the dark. We discuss these data with regards to our current developmental and genetic understanding of cavefish morphological and behavioral evolution.
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    Mechanism and evolutionary significance of the loss of melanin pigmentation in the cave fish Astyanax mexicanus.
    (2008-05-27) Hixon, Ernest R; Jeffery, William R; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The regressive evolution of traits such as eyes and pigmentation is common among cave organisms. As a model to study regressive evolution, I have used the teleost Astyanax mexicanus, which consists of eyed and pigmented epigean forms and many populations of cave-dwelling forms that have lost those traits. This study investigates the mechanism for the loss of melanin production, from the origin of chromatophores from the neural crest to the synthesis of melanin within the melanocyte. I show that cavefish retain a migratory population of neural crest derived cells that are tyrosinase positive and respond to exogenous signals as expected of a melanocyte. I then propose that the regressive evolution of melanin pigmentation is a selectively evolved trait that provides for an excess of dopamine, supported by the near two-fold increase in dopamine in cavefish brains, quantified via HPLC analysis. This study suggests that regressive evolution sometimes occurs via selection.