Astyanax mexicanus, also known as Mexican Tetra, is a freshwater fish of the Characidae family native to Central America. The surface and cave forms of the Mexican Tetra are used as models of morphological and behavioural micro-evolution. Some 30 caves are home to populations of cave-dwelling Astyanax mexicanus, divided into 3 geographical groups, possibly representing a case of convergent evolution.
Cave populations lost their eyes and pigmentation (adaptation to their habitat in total and permanent darkness), but developed other traits considered adaptive to cave life, in particular olfactory sensory compensations and lateral line. They also developed many behavioural traits grouped under the term “Cavernicolous Astyanax Behavioural Syndrome”, craniofacial changes, physiological changes, etc.
The two morphs of the species allow the study of the micro-evolution of development (evo-devo) underlying morphological evolution. Their cross-breeding allows quantitative genetic studies (QTL) to understand the genetic determinism of the evolution of traits. Comparative and functional genomics allows to understand the dynamics of molecular evolution, and to estimate the contributions of selection and genetic drift in the evolution of cave fish.
Sexual maturity reached at 6-8 months.
The Biology and Evolution of the Mexican Cavefish. Eds AC Keen, M Yoshizawa, SE McGaugh. Elsevier, Academic Press.
Retaux S., Pottin K, Alunni A., Biology of the cell, 2008