Meeting Abstract

P2-47   -   Comparing the visual spectral sensitivity of native surface Mexican Tetra ( Astyanax mexicanus ) with recently diverged cave populations Tait, TR*; Enriquez, MS; Gluesenkamp, AG; McGaugh, SE; Mensinger, AF; University of Minnesota Duluth; University of Minnesota Duluth; San Antonio Zoo; University of Minnesota Twin Cities; University of Minnesota Duluth tait0014@d.umn.edu

The Mexican Tetra, Astyanax mexicanus, is a fish with two morphotypes: a surface form, and a cave form that develops troglomorphic features including reduced pigmentation, vestigial eyes, and increased olfactory and lateral line sensitivity. While their native range extends from central/southern Mexico to the lower Rio Grande and Nueces River, several satellite surface populations were introduced to a Texas aquifer approximately 100 years ago and have shown evidence of rapid evolution in certain phenotypic traits. A recent study by McGaugh et al. (2020) comparing the morphological and behavioral data between surface and cave A. mexicanus in the Honey Creek Cave system indicated notable differences have developed over a relatively short amount of time. One native and five satellite populations (two surface and three cave) were tested and compared for dark-adapted visual spectral sensitivity using electroretinography (ERG). No differences were found between the native and satellite surface populations. However, significant differences in visual sensitivity were found at the wavelengths 530 and 560 nm (p < 0.05) between the Honey Creek Cave and surface populations. We hypothesize that the data indicates rapid divergence between the Honey Creek Cave population and the surface populations, where the cave population is less sensitive to light. This indicates that the recently diverged cave populations are undergoing retinal reorganization that may eventually lead to vestigial eyes.