Ayuyu (Coconut Crab)
If a coconut crab would go through a mutation, it would be much bigger than its usual size and and have the ability to live in water. The average size of a coconut crab is 60 cm, but once gone through mutation, it would be 90 cm long. Though they are part of the crab family, they are consider a land-living arthropod, in which they can't live in the water for long. But if it were to undergo a mutation, it would produce special lungs and gills similar to a fish gill so they would have the ability to breathe in water and roam around without limited time.
As it is in its mutation form, there would be differences among the regular and the mutated ones. Since they are 30 cm larger than an average coconut crab, it would affect the species with living in one habitat, which means competition with food and survival. The bigger crabs may take more than enough of the resources provided, leaving the average crabs with the least amount. Another part of mutation that would affect their species is respiration. Since the mutated ones have the ability to live in water, they might not only eat just plants or vegetation, but eat meat as well. They would then be considered predators in the marine habitat. That means the mutated crabs would be omnivores.
Due to the change the coconut crab has gone through, it would be beneficial for these mutated organisms. Through the adaptions they have developed, it would benefit there kind of species to survive and natural selection will give these species the ability to produce more offspring for the sake of their specie's survival.