Question

A cuticle occurs on the surface of organisms of many phyla and appears to be an advantageous feature. why have higher organisms not retained this structure?

Answer 1

While the cuticle has several advantages such as protection, they do not confer much advantage to larger eukaryotes. This is because of their limiting factor to growth (size). The cuticle would also restrict development of different skin structures such as fur.  Additionally, while the cuticle provides leverage for muscular movements on arthropods, nematodes, and flatworms, it is not necessary for larger animals since the same function is rendered by the endoskeleton.