Subterranean Fishes of the World

5726

2021

bioRxiv preprint December 17th 2021

Now published in Evolution and Development https://doi.org/10.1111/ede.12412

bioRxiv preprint. This version posted December 17, 2021. The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC 4.0 International license

Evolution in response to a change in ecology often coincides with various morphological, 17 physiological, and behavioral traits. For most organisms little is known about the genetic and 18 functional relationship between evolutionarily derived traits, representing a critical gap in our 19 understanding of adaptation The Mexican tetra, Astyanax mexicanus, consists of largely 20 independent populations of fish that inhabit at least 30 caves in Northeast Mexico, and a surface 21 fish population, that inhabits the rivers of Mexico and Southern Texas. The recent application of 22 molecular genetic approaches combined with behavioral phenotyping have established A. 23 mexicanus as a model for studying the evolution of complex traits. Cave populations of A. 24 mexicanus are interfertile with surface populations and have evolved numerous traits including 25 eye degeneration, insomnia, albinism and enhanced mechanosensory function. The interfertility 26 of different populations from the same species provides a unique opportunity to define the genetic 27 relationship between evolved traits and assess the co-evolution of behavioral and morphological 28 traits with one another. To define the relationships between morphological and behavioral traits, 29 we developed a pipeline to test individual fish for multiple traits. This pipeline confirmed 30 differences in locomotor activity, prey capture, and startle reflex between surface and cavefish 31 populations. To measure the relationship between traits, individual F2 hybrid fish were 32 characterized for locomotor behavior, prey-capture behavior, startle reflex and morphological 33 attributes. Analysis revealed an association between body length and slower escape reflex, 34 suggesting a trade-off between increased size and predator avoidance in cavefish. Overall, there 35 were few associations between individual behavioral traits, or behavioral and morphological traits, 36 suggesting independent genetic changes underlie the evolution of behavioral and morphological 37 traits. Taken together, this approach provides a novel system to identify genes that underlie 38 naturally occurring genetic variation in morphological and behavioral traits.

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