Saturday, June 18, 2011

Sand Collar Season....or More Tiny Stuff to Figure Out

The Moon Snail, Puget Sound's largest intertidal snail is currently in the middle of its breeding season (April-Sept).  Most sand and gravel beaches have egg cases (sand collars) in abundance.  The snails are separate sexes, with females growing faster and being larger than males.  Mating is rarely observed as it takes place under the sand or subtidally. Moon Snails begin to breed when about 2.2 inches in size.  Females can store sperm for up to 6 weeks before fertilizing the eggs which are mixed with a mixture of sand and glue and extruded in the form of a collar.  If you are really lucky you may witness this process by observing a collar sort of magically emerging from the sand.  The whole process takes about 20 to 40 minutes.  In all instances of witnessed egg laying I have seen the female has been upside down in the sand while laying the eggs (only dug up after eggs were laid).  The sand collar contains some 3 hundred plus thousand eggs.
Life expectancy is about 14 years maximum.
Adults feed on clams and other snails which they either drill with the rasping radula or suffocate.  Drilling is assisted with an organ that produces enzymes and hydrochloric acid to weaken the shell of the victim.
Drilled holes are countersunk which distinguishes them from holes drilled by other snails or octopuses.
Drilling rate is about 0.5mm per day and the process of eating the prey take about a day.  Moon Snails favor soft or thin shelled clams and avoid the thick shell Heart Cockles.  In turn Moon Snails is fed upon by Sunflower Stars, Red Rock Crabs, gulls, octopuses, and when small, Northern Clingfish and likely other fish.
While some people do eat Moon Snails, certain First Nations peoples of Canada did not as they were said to make the eater stupid.  Since Moon Snails feed on clams which may contain toxins that can affect brain function this seems like quite good advice...Don't eat them.

If one closely examines the concave surface of a sand collar on the beach it becomes evident that lots of things are using it to lay eggs, perhaps as cover, or feeding on the Moon Snail eggs.  Some of the items found are tiny and difficult to identify which makes it all the more interesting....if sometimes frustrating for anyone who wants to know it all.  Images below show some of the action on the collar surface.

SAND COLLAR STUFF (many of these are 1cm or less in size)

Lacuna snail on sand collar

Dove Snails on sand collar

Barnacle Eating Sea Slug on sand collar

Flat Worms

Opalescent Sea Slug

Barnacles on sand collar

Top Snail on egg mass on sand collar

Unidentified worm on sand collar

Top Snail on sand collar

Moon Snail with sand collar

Moon Snail with clam victim

Moon Snail making sand collar
Moon Snail siphon on surface collecting air

Moon Snail damaged shell from gull attack

Moon Snail drilled clam

Opalescent Sea Slug eggs

Hansine's Sea Slugs eating Opalescent Sea Slug eggs (?)
Phyllodoce williamsi  Worm eggs

Olea hanisneensis  sea slug eating Opalescent Sea
Slug eggs

Olea hanisneensis sea slug on sand collar

Lacuna snail and eggs

Opalescent Sea Slug Ho Down

Flatworm with flatworm eggs on sand collar

Unidentified snail on sand collar
Teamwork, Olea Sea Slug style
Lacuna with decaying seaweed wit
h unknown white pattern


  1. I love your photos! Several times, they've helped me to identify a new critter. This time, it was the flatworm eggs. Last time, it was the green egg rings of the Pyllodoce williamsi, on this same post. (I keep coming back to the same pages.)

    I am writing about the flatworm eggs on my blog, as I posted a photo of some two weeks ago, without knowing what they were.I hope it's okay with you that I am borrowing your photo for comparison, with links back to here, of course. I hope you don't mind: I couldn't find any notice about copying. If you'd rather, I'll remove the photo and just keep the links.

    Thanks, anyway, for the great work!

  2. The post containing your photo, and a bit about this site, is here:

  3. Hello,

    I am the editor of Naturally Kiawah, the magazine of the Kiawah Conservancy in South Carolina. We are featuring an article in our next issue on items found on our beach. Would you be able to allow us to use your image of a sand collar? Do you have an image of a moon snail as well? We are a 501 (c) 3 organization with no budget to pay but we would, of course give you full credit.

    Do not heistate to contact me with any questions.

    Kind regards,

    Shauneen Hutchinson

  4. Hi Shauneen,
    Yes, you have permission to use any image you find on my blog for educational nonprofit use. There are moon snail images on some posts but I can send you one email also if you need.


  5. I took a look at your Naturally Kiawah publication on line........Outstanding publication.