The story of the Mexican cave fish, Astyanax mexicanus, an intriguing example of how environmental stressors play a role in the development, adaptability, and diversification of an organism. Shown in the image is the mexicanus species, noticeably different from its surface counterpart in that it does not have developed eyes and lacks pigmentation.
Recent findings support the idea that the cave species arose when surface fish were trapped in cave waters, raising the levels of stress in the animals. As the thinking goes, triggering stress pathways destabilize a network of proteins that normally works to stabilize phenotype, leading to altered gene expression. Such conditions will lead to increased phenotypic variation, including the development of eyes in subsequent generations.
Which of the following choices is a feasible explanation for the selective advantage of individuals with diminished or no sight?

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