Elephant tusk shell
The elephant tusk shell is a marine mollusk belonging to the class Scaphopoda and the genus Dentalium, which includes around 50 living species of tusk shells. Named for its elongated, tusk-like shell, this small animal typically measures between three and five inches long and features a tube-shaped, curved structure that tapers at one end. The shell is composed of calcium carbonate, providing protection for the soft-bodied animal inside.
The elephant tusk shell inhabits the ocean floors of temperate and tropical regions, where it burrows into sand and mud, leaving the pointed end of its shell exposed. It moves by extending its muscular foot to clear a path and pull its shell along, using clusters of tentacles to sense the environment and capture microscopic organisms for food. Unlike many mollusks, it lacks gills; instead, it absorbs oxygen through its mantle lining.
Reproduction occurs through a spawning process, wherein males release sperm into the water to fertilize the eggs of females, leading to the development of a planktonic larva that eventually settles to the ocean floor. The lifespan of the elephant tusk shell remains unknown, contributing to the mysteries of its biology and ecology.
On this Page
Subject Terms
Elephant tusk shell
The elephant tusk shell is one of the 900 species of tusk, or tooth, shells from the class Scaphopoda. This small animal is named for the shell it lives in, which is shaped like the tusk of an elephant.
Kingdom: Animalia
Phylum: Mollusca
Class: Scaphopoda
Order: Dentaliida
Family: Dentallidae
Genus: Dentalium
Species: Elephantinum
The elephant tusk shell belongs to one of the seven classes of mollusks and the genus Dentalium, which contains about 50 extant, or living, species of tusk shells. As a mollusk, the elephant tusk shell animal has a hard shell made of calcium carbonate. Mollusks have a great variety of shell shapes, but this animal has one in the shape of an elephant's tusk. The body of the animal releases the material from its body to form the shell about itself. The shell of the elephant tusk shell is between three and five inches (7 1/2 and 13 centimeters) long. It is tube-shaped and curved, and it tapers from a wide, round opening at one end to a smaller, narrow, round opening at the other end.
A fold of skin, called a mantle, lines the inside of the shell. Many tiny hairs, called cilia, line the mantle and wave back and forth to create water currents. These currents draw water into the shell's small opening. The mantle absorbs the oxygen from the water so the elephant tusk shell can breathe. Other parts of the skin may also absorb oxygen. This type of mollusk does not have gills. The mantle protects the animal's soft body parts. The elephant tusk shell creature has a soft, three-part body. These three parts are a head, a section which contains its organs, and a muscular foot.
The elephant tusk shell lives along the bottom of the world's temperate and tropical oceans and may be found either in shallow waters or at great depths. It burrows the thick end of its shell at an angle into the sand and mud and leaves the small, pointed tip of its shell poking above the surface of the bottom. The shell moves along the bottom by extending its muscular foot from the wide opening to clear a space and to pull the shell behind it.
Two clusters of club-shaped tentacles move about in the space formed by the foot and sense the shell's surroundings as well as find food. These tentacles are important since the elephant tusk shell does not have eyes in its head. The head extends from the opening alongside the foot, while the chamber which contains the animal's organs remains inside the shell. The tentacles pass food to the small mouth. The diet of the elephant tusk shell includes a number of microscopic organisms, such as foraminiferans. It may also feed on detritus, or small particles of plants and animals in the sand and mud. In the mouth of the elephant tusk shell is its radula. The radula of the elephant tusk shell is like a tongue with sharp teeth or edges on it. The radula breaks food into pieces, and hard plates in the gizzard, or stomach, crush the shells of the foraminiferans.
Like many other mollusks, the elephant tusk shell reproduces by spawning. This process involves a male tusk shell releasing its sex cells, called sperm, into the water in order to fertilize a female shell's eggs which she releases into the water. Each fertilized egg then hatches into an oval- or pear-shaped larva called a trochophore. Each larva swims freely in the planktonic levels of water. These are the levels, usually near the surface of the water, where tiny creatures called plankton live. An elephant tusk shell larva soon grows and settles to the bottom to become an adult tusk shell.
The life span of the elephant tusk shell is not known.
Bibliography
“Dentalium Elephantinum.” Mindat - Mines, Minerals and More, www.mindat.org/taxon-2284900.html. Accessed 26 Apr. 2024.
“Mollusca.” Animalia, www.animalia.bio/mollusca. Accessed 26 Apr. 2024.
Mulcrone, Renee Sherman. “Scaphopoda.” Animal Diversity Web, 2005, animaldiversity.org/accounts/Scaphopoda/. Accessed 26 Apr. 2024.