Subterranean Fishes of the World

4460

2019

Biology Letters

15:20190554

Eye regression occurs across cave-dwelling populations ofmany species and is often coupled with a decrease or loss in eye function. Teleost fishes are among the few vertebrates to undergo widespread colonization of caves and often exhibit eye regression with blindness. Cave populations of the poeciliid fish Poecilia mexicana (cave molly) exhibit reduced—albeit functional—eyes, offering the opportunity to investigate partial eye regression. We sequenced eye transcriptomes of cave and surface populations of P. mexicana to identify differentially expressed genes that potentially underlie eye regression in cave mollies. We identified 28 significantly differentially expressed genes, 20 of which were directly related to light sensitivity, eye structure and visual signaling. Twenty-six of these genes were downregulated in cave compared to surface populations. Functional enrichment analysis revealed eye-related gene ontologies that were under-representedin cavemollies. In addition, a set of co-expressed genes related tovisionandcircadian rhythmwas correlatedwith habitat type (cave versus surface). Our study suggests that differential gene expression plays a key role in the beginning evolutionary stages of eye regression in P. mexicana, shedding further light on regressive evolution in cavefish.

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