A central question in biology is how naturally occurring genetic variation accounts for morphological and behavioral diversity within a species. The Mexican tetra, Astyanax mexicanus, has been studied for nearly a century as a model for investigating trait evolution. In March of 2019, researchers representing laboratories from around the world met at the Sixth Astyanax International Meeting in Santiago de Querétaro, Mexico. The meeting highlighted the expanding applications of cavefish to investigations of diverse aspects of basic biology, including development, evolution, and disease-based applications. A broad range of integrative approaches are being applied in this system, including the application of state-of-the-art functional genetic assays, brain imaging, and genome sequencing. These advances position cavefish as a model organism for addressing fundamental questions about the genetics and evolution underlying the impressive trait diversity among individual populations within this species.

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The development of animal model systems is dependent on the standardization of husbandry protocols that increase fecundity and reduce generation time. The blind Mexican tetra,Astyanax mexicanus, is an emerging genetic vertebrate model for evolution and biomedical research. Surface and cave populations ofA. mexicanushave independently evolved, providing a model system for studying the genetic basis of divergent biological traits. While a rapid increase in the use ofA. mexicanushas led to the generation of genetic tools including gene-editing and transgenesis, a slow and inconsistent growth rate remains a major limitation to the expanded application ofA. mexicanus. The optimization of husbandry protocols that maximizes high-nutrient feed, smaller tank densities and larger tank sizes across development, would facilitate faster growth and expand the use of this model. Here, we describe standardized husbandry practices that optimize growth through a high protein diet, increased feeding, growth sorting of larvae and juveniles, and tank size transitions based on standard length. These changes to husbandry had a significant effect on growth rates and decreased the age of sexual maturity in comparison to our previous protocols. To determine whether our nutritional change and increased feeding impacted behavior, we tested fish in exploration and schooling assays. We found that a change in diet had no effect on the behaviors we tested, suggesting that increased feeding and rapid growth will not impact the natural variation in behavioral traits. Taken together, this standardized husbandry protocol will accelerate the development ofA. mexicanusas a genetic model.

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