Dive Dry with Dr. Bill

#597: Mating and Munching of the Giant Escargot

One of my real joys during summer is to squeeze myself into my wetsuit, gather my SCUBA and video gear and head down to the dive park about the time it is getting dark. While I'm certainly no loner, I do enjoy the feeling of being down under all by myself in the park to enjoy the action. Why, it's almost better than the Marlin Club at night, and would certainly top it handily if I ever found myself confronted by a lovely mermaid! At least she wouldn't be able to hear my awful "pick up" lines with a regulator in my mouth.

Before I headed down to the Dutch Antilles last month, I went down to our dive park one night to see what I could see. I was surprised to find the surface was quite choppy and it was evident I'd encounter a lot of surge on my dive. Not good for filming since it is hard to stabilize in the shallows and the kelp and other algae tend to whip around a lot, ruining my video. Once I descended, I noted not only was there surge, but a reasonably strong current. The kelp had been pulled down by it so it was horizontal and parallel to the bottom. Entanglement can become a real issue under those conditions. However, I was committed (and not by my psychiatrist this time).

I slowly worked my way out toward the harbor mouth in fairly shallow water. The bass were bountiful and kept stirring up the sediment making it difficult to film. I barely got two of them on video capturing the poor innocent blacksmith. One even tried to get a lobster! I had seen a kelp bass do that on my last night dive, but it immediately spat it out. I was disappointed that I wasn't seeing much of interest to film... and even when I did, the conditions often prevented me from taking any usable footage.

On my way back to the stairs, I stopped to shoot a wavy top snail with its foot exposed. During the day, these large snails are generally stuck tight to the rocks so the large sheephead like Oscar I, II and III don't dislodge them, crush their shells and enjoy a big tasty escargot. Back when I first arrived on the island back in the late 1960s, I encountered these fairly large snails diving the waters off Toyon. I also saw many of them in the Native American middens on the archaeological digs the school did. I must admit I've never tried them. My only experience with escargot was when my then girlfriend Sarah and I were invited by Packy Offield's mother to dine at the historic Drake Hotel in Chicago back in the early 1980s. The snails tasted a lot like butter!

As I was filming the snail's foot, I noticed wisps of white streaming around its shell. It turned out there was another wavy top snail attached to its shell... and it was releasing clouds of its gametes! Then the snail I had been filming started to do so as well. Three other snails tried to join the pair... does that make it a menage a cinq (which is pronounced like "sank")? Given the substantial water motion, I had to grip what I could of the rock with one hand and hold my camera out in the other. Good thing I have strong wrists due to all my typing as that is hardly a recommended filming position!

Apparently these snails are not sexually mature until they reach a shell diameter of 3-3 1/2 inches. Wavy tops will reproduce any time of year (my kind of species), but often show peaks in spring and fall. Scientists have found that growth in these snails slows down in spring and summer but picks up in fall and winter. I'll go out on a limb (er, kelp frond) and suggest that growth may slow during periods of more intense spawning since allocation of ingested nutrients would be dedicated toward producing gametes rather than increasing body size. My hypothesis was just confirmed by Fish & Wildlife as I researched this column.

When I first arrived on the island, this snail was known scientifically as Astrea undosa which is the name I often use today. However, it was also called Megastrea undosa before its name was changed to Lithopoma undosum. I can hardly wait to see what they call it next! It is native to the Californias, being found from Point Conception down into northern Baja down to about 70 feet deep usually on rocky shores with kelp forests. Scientists report that smaller snails are usually found in shallow water while the big ones go deep due to the impact of water motion and competition from other herbivores. However, on Catalina's more sheltered leeward coast large ones can be found in pretty shallow water.

To defend itself from hungry sheephead, this snail has a thick, very sculpted calcium carbonate shell. They must be a bit top heavy as they are often turned over by the surge... or hungry predators. When this happens, they close up tight using a thick trap door known as the operculum. Shells may be 4 1/2 inches in diameter and up to nearly six inches in length. It has wavy ridges on the outside from which this member of the turban snail family gets its common name. The outside of the shell often has a brown layer or coating known as the periostracum. The shells often have algae or invertebrates growing on top of them. I've often seen the nasty invasive exotic Sargassum horneri growing on the shells, occasionally reaching several feet in length!

In addition to the crushing jaws of large sheephead they may fall prey to starfish which pry them off the rocks. Their snail cousins the Kellet's whelks are also known to munch on them Lobsters eat them and chew on the calcium-based shells to provide nutrients to build their exoskeletons. One of the more interesting predators is the octopus. Once they have consumed the critter inside the shell, octos often use the empty (or occasionally an occupied) shell to defend themselves against predators. They grasp the shell in their eight arms and pull it tight against the entrance of the hole they hide in. Pretty ingenious to use one's food to prevent becoming food for something else!

It is commonly believed by scientists that wavy tops feed on microscopic algae attached to the rocks they crawl over. However, I frequently see them munching away on pieces of giant kelp they have trapped with their muscular "feet." Now would you rather munch on itsy bitsy teeny weeny algae or chow down on a nice big juicy blade of giant kelp? I say go for the gusto... and supersize it!

Speaking of supersizing it, there is a young but growing commercial fishery for these snails in southern California and northern Baja, largely centered around San Diego. Fortunately the commercial take is prohibited within 1,000 feet of shore which places it in very deep water off the Channel Islands. Apparently it began in the early 1990s and was undertaken in part by former urchin harvesters. It is gathered both for the meat and the shell which is used to make buttons. Fish & Wildlife refers to the meat, considered a substitute for abalone, as "wavalone." In Mexico they refer to it as caracol panocha. I think I'll just call it "escargot géant" if you speak the language of love like I don't!

© 2014 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Close-up of butter hamlet; two "he-she" butter hamlets doing "the wild thing" and a jealous barred hamlet looking on

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