Eyes Under Puget Sound: Critter of the month — dove snails

 
Three images from left to right, one white bird, and two shells. The first shell says, "alia carinata," and the second shows,"microscopic ax

Left: White Dove by Sander van der Wel (Netherlands).  
CenterAlia carinata collected from Puget Sound.
Right: Close-up of the shell of Astyris gausapata, showing microscopic vertical lines called axial striations.


The holidays are in full swing — and what could capture the spirit of the season better than the dove — the universal symbol for peace, love, and goodwill? You might not know it, but a different kind of beautiful dove lives under the wintry waters of Puget Sound.
 

Birds of a feather?

Label says, "Kingdom, Animalia; Phylum, Mollusca; Class, Gastropoda; Order, Neogastropoda; Family, Columbellidae."

Dove snails don’t look much like their avian namesake — except for the teardrop shape of their shells (and the opening, or aperture, might be able to pass for a wing if you’re feeling creative). Perhaps the diverse patterns of sculpture and color on their shells reminded some naturalist long ago of a dove’s mottled feathers.
 
Taxonomists can’t always trust these color patterns when trying to distinguish similar-looking species. For example, the two species of dove snails we encounter most commonly in Puget Sound are the nearly identical Alia carinata (the carinate dove snail) and Astyris gausapata (the shaggy dovesnail). Both species have white, orange, and brown markings, so it’s their shell texture that gives them away. A. carinata has a smooth shell, while A. gausapata has fine vertical raised lines called axial striations.
 

Lip reading

Did you know that snails have lips? Well, maybe not true lips like we have, but the flared part of the opening in a snail’s shell is called the outer lip, and it can be another clue for a taxonomist trying to tell similar species apart. A. carinata has a carinate shoulder, meaning that the top part of the upper lip is pronounced and sticks out. In addition, A. carinata’s outer lip is much thicker and darker in color with heavier, more noticeable “teeth” on the interior edge. 
 
Two shells, each showing where the opening is. A third picture a series of serated leaf-like structures lined up in columns.

Left: Aperture (opening) of Astyris gausapataCenter: Aperture of Alia carinataRight: Gastropod radula: Hershler R. & Liu, H.P. (2011).

Sharp-tongued

Dove snails don’t use the teeth on their shells for chewing — like most mollusks, they have a much more specialized feeding tool. A tongue-like projection called the radula helps the snail scrape up food before it swallows. The dove snail’s radula is covered in tiny serrations that are replaced as they wear down. Puget Sound’s dove snails are carnivores; they use their radulas to chew up marine worms and crustaceans, or to grind down the shells of other mollusks. So much for peace on Earth!  If they can’t find enough prey, detritus (decomposing organic material) is their second choice.


Shut the front door

This shaggy dove snail

This shaggy dove snail has its operculum pulled closed for protection.

Like all mollusks, dove snails build their shells around themselves using calcium carbonate found in the environment. The coiled shell allows the animal to withdraw inside when it is threatened. It even has a “front door” it can open and close. As the snail retracts, it pulls the soft tissue of its muscular foot behind it. Attached to the end of the foot is a protective plate called the operculum that seals the aperture up tight.


When doves cry

Sometimes a hard shell and an operculum aren’t enough to protect from predators. In some parts of the world, humans collect dove snails for their colorful shells, making them into souvenir necklaces or even using them as a food source.

The Puget Sound species are too tiny for people to eat, but shore birds and fish eat them by picking them off intertidal rocks, kelp, and eelgrass. The empty shells of the unlucky snails make perfect dwellings for tiny hermit crabs — so even after they are gone, the dove snails are able to give other animals the precious gift of a home.
 

Critter of the month

Our benthic taxonomists, Dany and Angela, identify and count sediment-dwelling organisms as part of the Marine Sediment Monitoring Program. They track the numbers and types of species they see in order to understand the health of Puget Sound and detect changes over time.

Dany and Angela share their discoveries by bringing us a benthic Critter of the Month. These posts will give you a peek into the life of Puget Sound’s least known inhabitants. Can't get enough benthos? See photos from our Eyes Under Puget Sound collection on Flickr.