The tube which runs through the partitions of chambered cephalopod shells.
Living cord which connects all the chambers in septate shells. Synapomorphy of the Cephalopoda.
The Siphuncle is a tube - which may be thick or slender - which runs through each of the internal chambers ( camerae) of the shell, from the base of the living chamber to the apex. It consists of soft and shelly parts, including septal necks, connecting rings, calcareous deposits, and siphuncular cord. Nautiloids are classified by the nature of the siphuncle and its position within the shell.
A thin tubular extension of the back of living Nautilus to the origin of the shell. It regulates the buoyancy of the whole animal. It is present in fossil nautiloids and ammonites, and is believed to serve the same function.
n. A strip of tissue running between the compartments of a cephalopod's shell that helps the animal achieve neutral buoyancy.
A tube connecting the chambers of nautiloids and ammonoids which allows the organisms to control the fluid content of each chamber, and thus its buoyancy.
The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and Spirula. In the case of the cuttlefish, the siphuncle is indistinct and connects all the small chambers of that animal's highly modified shell; in the other cephalopods it is thread-like and passes through small openings in the walls dividing the chambers of the shell.