African rail
These birds probe with their bill in mud or shallow water, also picking up food by sight. They mainly eat insects, crabs and other small aquatic animals.
Water vascular system
Ophiuroids, the group including brittle stars and basket stars, have a somewhat different water vascular system from sea stars, despite their superficially similar appearance. The madreporite is located on the underside of the animal, usually in one of the jaw plates. The stone canal runs upwards to the ring canal, typically located in a circular depression on the upper (i.e. internal) surface of the jaws. The ring canal has four polian vesicles.