Range: Marine waters worldwide

Habitat: Seafloor in shallow waters and deep ocean

Size: Less than 1 inch - 6 inches (2.54-15.24cm) long

Diet: Detritus

Threats: Sea snails, fish, and crustaceans

Lifespan: Unknown

Transcript:

Today on Animal Fact Files we’re discussing tusk shells. These mollusks are also known as tooth shells, and they get these common names due to their shell shape. Don’t they kind of look like an elephant tusk or a canine tooth? Their scientific name means something along the lines of “shovel foot” and is in reference to their burrowing behavior.

There are somewhere around a thousand described tusk shell species, and about half of these are alive today. They live in marine waters from polar regions to the tropics. They’re benthic creatures meaning they’re found along the seafloor. They may live well over three miles (4,800m) below the ocean’s surface, but they can be found in shallow areas starting around twenty feet (6m) deep! As adults, they live in sandy or muddy sediment, burrowing just under the sediment’s surface or to depths many times their body long. In size, living tusk shells range from under an inch to half a foot long.

Tusk shells burrow in the sand headfirst to find food; so, like barnacles, they spend most of their lives upside down! They have a muscular foot which holds them in place and tentacles with adhesive tips that reach out into the sediment to collect food. Food for a tusk shell includes microscopic plants and animals often termed “detritus”. These food particles are brought to the tusk shell’s mouth and ground up by the radula which acts like a nail file on fingernails. We’ve discussed the radula previously in our gumboot episode.

Predators to tusk shells include other mollusks like sea snails as well as fish and crustaceans. It’s believed that the tusk shell’s burrowing behavior helps camouflage them from predators and may keep them safe from harm. They may dig deeper if they sense a threat, though it should be noted that tusk shells do not have eyes.

Unlike other mollusks, like snails, the tusk shell’s shell opens at both ends. The head and tentacles are found at the wider, front end, while the back end is where water is taken in and expelled from the animal’s body. This is how they get oxygen, though they don’t have gills! The oxygen is absorbed through the mantle. The mantle is also the part of their body that produces their shell!

Tusk shells are either male or female and they release their respective reproductive bits into the water column where they are fertilized externally. In both males and females, the eggs and sperm are released through what is essentially the adult’s right kidney. After fertilization occurs, the eggs hatch into free swimming larvae which float for about a week before settling to the ocean’s surface and undergoing the process of becoming an adult.

One way you may have seen evidence of these animals is how their shells are used. Hermit crabs, who do not make their own shells and use the shells of other animals, have been known to use empty tusk shell shells as their homes!

For more facts on tusk shells, check out the links below. Give a thumbs up if you learned something new today. Thank you to our Patrons SpikeSpiegel93, Dad, and everyone else for their support of this channel! And thank you for watching Animal Fact Files!