suggest what physiological structural or behavioral features might be important to the striped shore crabs survival

When talking about natural selection, it is often said that the strongest are those who survive. And this is not at all like that. In reality, those who are going to survive and have offspring will be the ones most adapted to the prevailing conditions at that time. There are features that evolve secondary to an adaptation. For example, in the case of the crab, associated with the adaptation of behavior that involved taking refuge in a shell, a series of anatomical adaptations emerged that give the crab more facilities for that way of life.