Subterranean Fishes of the World

3898

2016

Astyanax mexicanus are Characin fish with a cave fish morph and a surface fish morph that are able to successfully interbreed, which provides us with an evolutionary-genetic model of cave adaption. These two morphs have evolved numerous differences in eye size, pigmentation, and scleral ossification. The focus of this research is the sclera, the tough outer wall of the eye, and the patterns of scleral ossification in cavefish-surface fish hybrids. Our previous research determined that two to three genes likely influence the presence/absence of scleral ossicles. In this study, we expanded the sample size of our previous analysis in order to (1) confirm the two to three gene model and (2) detect quantitative trait loci (QTL) responsible for scleral ossification. In order to answer these two questions, we assessed photographs of surface fish and cavefish F2 hybrids for the presence/absence of zero (0), one (1), or two (2) scleral ossicles. We then analyzed their distribution among the F2 via a X² test and used a genetic linkage map of over 100 microsatellite markers to identify the location of QTL responsible for scleral ossification. We found that scleral ossification follows a recessive threshold model of inheritance because the majority of individuals sampled had one or more scleral ossicles. While the X² results were consistent with a two-locus model of threshold inheritance for the loss of scleral ossification, the QTL analysis identified three QTL on linkage groups 4 and 18. Scleral ossification remains a complex trait with limited knowledge behind its genetic characterization. This study provides insight into the number and location of genes controlling the formation of scleral ossicles in Astyanax mexicanus, which may be applied to human ocular diseases such as phthisis bulbi.

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23rd International Conference on Subterranean Biology

2016

2016

2016