Cave-dwelling catfish and cave-dwelling salamanders share striking similarities: both organisms lack pigmentation, and their eyes are reduced or absent. the most recent common ancestor to these organisms had normal pigmentation and fully developed eyes. the similarities between cave catfish and cave salamanders are an example of

The correct answer is - convergent evolution.

The cat fish and the salamander are animals that belong to separate families, they have totally different life-style, physical appearance, and role in the ecosystems. On the other hand, the cave-dwelling catfish and the cave-dwelling salamander, despite having ancestors that do not look alike nor are of a same family, they share striking resemblance. The reason for their resemblance is the environment in which they live, where they had to evolve the same or very similar traits that would be advantageous for survival, so they actually started to look very similar. That evolutionary occurrence is called convergent evolution, where we have two animals that have totally different ancestors, but evolved to look alike because of the environment.