Solution

One of the best-known examples of commensalism is that between the hermit crab and a sea anemone (e.g., Adamsia). The anemone is often found attached to the shell in which the hermit crab lives. A sea anemone attaches itself to the crabs shelter and it may envelop part of the crab's shell as well. The growth of the crab and anemone keep pace with each other and the crab has no need to change its shell more and more of its is sheltered by the anemone. As the crab moves about in search of food the anemone is brought into contact with a greater supply of food and the crab is protected by the anemone's stinging cells.