Last week at 7 a.m., on my only day off, I received a call from Captain Tom Testeverde in Gloucester.  

His son, Captain Tom Jr., had just brought in the fishing vessel Midnight Sun with some animals for me. So, off I went down to Fishermen’s Wharf in Gloucester to meet his boat and pick up some critters for the Oceanarium. I had coolers with bottles of saltwater ice and an aerator for the car to keep them alive on the trip home. I thanked the crew for keeping them alive and made my way back to Hampton.

I had a trove of unique animals, among them were three huge moon snails. Now the other animals I could keep safely in my tank, but these snails were another story. 

To explain my dilemma, I’ll need to give you a short biology lesson.  

Moon snails (Euspira heros) are a large round snail with a huge mantle/foot which not only extends out past their shell but envelops it as well. At times it covers all but the very top of its shell. They produce large quantities of mucus from it that allows them to slide along the sandy sea floor. They are also carnivores. Yes, they eat other snails and clams including each other.  

Have you ever seen a shell with a perfectly round hole in it? It looks like someone drilled a hole, well, they did. The moon snail crawls atop another mollusk (clams and snails) and secretes an enzyme that softens their shell. Then they rub a circular motion with their radula (part of their mantle or foot with hard calcareous ridges) along the area that was softened by the enzyme. 

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Eventually they “drill” right through the animal’s shell and push their own proboscis (long pipe like mouth part) through the hole and digest the animal inside of its shell, finally sucking the partially digested material out. Gruesome but true!

The problem with placing these animals in a tank with the other critters is twofold. Moon snails, as I said, secrete prodigious quantities of mucus fouling the water in the tank. 

They also will envelope and eat any other mollusk in the tank. What to do? 

I had to keep them in a separate cooler for the night for the other animals’ protection.

Most snails are hermaphrodites, that is they can be male or female at different times, but the moon snail is born a sex and remains that sex throughout its life. They come into the subtidal area during the summer months from deep water to find a mate and breed. Mating occurs and the female covers her shell with her foot and buries herself in the sand. 

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At this point, she begins to cover her foot with mucus and sand. When completed she begins to lay her eggs under the sand (up to 500,000!) and finally she covers the eggs with another layer of sand. An egg sandwich! She then pulls her foot and shell down deeper into the sand by blowing seawater beneath her and crawls away from the egg mass. She leaves a “sand collar” behind. The eggs develop and finally hatch into free swimming larval stages, eventually developing a shell and sinking to the bottom to repeat the process.  

These snails can grow to 5 inches and live up to 15 years.  

When walking on the beach you can spot pieces of the sand collars in the seaweed. They look amazingly like wet cardboard but on closer inspection if you turn them over you will see the remains of the eggs on the underside.

Now back to my dilemma, where to keep them? Every day I put them into my touch tank for visitors to view and touch, carefully. The reaction to touching this animal’s foot is always the same. They pull their hand away, make a face then back they go to touch it again.  

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At night I have given them a private tank to wander in and delightedly release quantities of mucus in privacy. Keep your eyes open when walking the beach for these beautiful shells and their egg masses.

For a hands-on experience, you can visit the Oceanarium while these gooey animals are in residence. They will be returning to their native habitat later this summer. We will be waiting excitedly for more unique animals to arrive from Gloucester and the Gulf of Maine.

Ellen Goethel is a marine biologist and the owner of Explore the Ocean World at 367 Ocean Blvd. at Hampton Beach.