Strombidium (stom-bid-ee-um) is one of the oligotrich ciliates. Traditionally grouped with the more widely reported tintinnids, but unlike tintinnids, these cells are naked and have no internal skeletal elements. There is a spiral Adoral Zone of Membranelles around the anterior of the cell and these are used to collect bacteria, algae and other small particles as food. Free-swimming. Common. Phase contrast.