Are all crustaceans arthropods?
Some crustaceans like barnacles do not appear to have legs or body segments. However, these features can be seen on barnacle larvae. These are barnacles that are not yet adults and have not attached themselves to anything yet. Legs and body segments disappear from adult barnacles because they are not needed. The barnacle is still considered an arthropod because the features that define arthropods can be seen on it during part of its life.