Biology subjects

Abdelaziz, J.

Publications and source records attributed to Abdelaziz, J..

3 recordsLinked to original sources

bioRxiv2025

Analysis of multi-trait evolution across independently evolved cavefish populations reveals shared and independent evolution of suites of cave-associated traits

Environmental perturbations often lead to the evolution of multiple traits. Determining whether shared genetic factors underlie multi-trait evolution is a central question in evolutionary biology. In the Mexican tetra, Astyanax mexicanus, cave-dwelling populations have repeatedly evolved multiple traits. The repeated evolution of these traits, paired the robust environmental differences between the surface and cave habitats, provide an opportunity to investigate the genetic basis of multi-trait evolution. Here, we investigate the extent to which shared genetic mechanisms underlie the repeated evolution of multiple traits in cavefish. Across cave populations, we find evidence for shared and distinct genetic mechanisms contributing to the evolution of individual traits. Further, multiple traits covary in cave-surface F2 hybrids and many of the same trait correlations are found across independently evolved cave populations. Finally, we assessed traits that differ between pigmented and albino F2 fish in surface fish with mutations in the albinism gene oculocutaneous albinism 2 (oca2). This revealed that mutations in oca2 reduce bottom-dwelling behavior in A. mexicanus. Together, these findings suggest that multi-trait evolution occurs repeatedly through shared genetic factors across A. mexicanus cave populations. These results are consistent with pleiotropy or linkage playing a large role in multi-trait evolution in this species.

evolutionary biology↗

bioRxiv2024

The rx3 gene contributes to the evolution of eye loss in the cavefish Astyanax mexicanus

Uncovering mechanisms by which sensory systems evolve is critical for understanding how organisms adapt to a novel environment. Astyanax mexicanus is a species of fish with populations of surface fish that inhabit rivers and streams and cavefish that have adapted to life within caves. Cavefish have evolved sensory system changes relative to their surface fish counterparts, providing an opportunity to investigate mechanisms underlying sensory system evolution. Here, we report the role of the gene retinal homeobox 3 (rx3) in cavefish eye evolution. We generated surface fish with putative loss-of-function mutations in the rx3 gene using CRISPR-Cas9 to determine the role of this gene in eye development in this species. These rx3 mutant surface fish fail to develop eyes, demonstrating that rx3 is required for surface fish eye development. Further, rx3 mutant surface fish exhibit altered behaviors relative to wild-type surface fish, suggesting that the loss of eyes impacts sensory-dependent behaviors. Finally, eye development is altered in cave-surface hybrid fish that inherit the mutant allele of rx3 from surface fish relative to siblings that inherit a wild-type surface fish rx3 allele, suggesting that cis-regulatory variation at the rx3 locus contributes to eye size evolution in cavefish. Together, these findings demonstrate that, as in other species, rx3 is required for eye development in A. mexicanus. Moreover, they suggest that variation at the rx3 locus plays a role in the evolved reduction of eye size in cavefish, shedding light on the genetic mechanisms underlying sensory system evolution in response to extreme environmental changes.

evolutionary biology↗

bioRxiv2024

Mutations in the albinism gene oca2 alter vision-dependent prey capture behavior in the Mexican tetra

Understanding the phenotypic consequences of naturally occurring genetic changes, as well as their impact on fitness, is fundamental to understanding how organisms adapt to an environment. This is critical when genetic variants have pleiotropic effects, as determining how each phenotype impacted by a gene contributes to fitness is essential to understand how and why traits have evolved. A striking example of a pleiotropic gene contributing to trait evolution is the oca2 gene, coding mutations in which underlie albinism and reductions of sleep in the blind Mexican cavefish, Astyanax mexicanus. Here, we characterize the effects of mutations in the oca2 gene on larval prey capture. We find that when conspecific surface fish with engineered mutations in the oca2 allele are hunting, they use cave-like, wide angle strikes to capture prey. However, unlike cavefish or surface fish in the dark, which rely on lateral line mediated hunting, oca2 mutant surface fish use vision when striking at prey from wide angles. Finally, we find that while oca2 mutant surface fish do not outcompete pigmented surface siblings in the dark, pigmented fish outcompete albino fish in the light. This raises the possibility that albinism is detrimental to larval feeding in a surface-like lighted environment, but does not have negative consequences for fish in cave-like, dark environments. Together, these results demonstrate that oca2 plays a role in larval feeding behavior in A. mexicanus. Further, they expand our understanding of the pleiotropic phenotypic consequences of oca2 in cavefish evolution.

animal behavior and cognition↗