Snails in our lives

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There are more different species of snails than any other type of mollusk, and most of us think of them as being of little importance other than becoming too numerous at times. However, Phil Pash, in a recent column in The Rock River Times, brought to our attention the potential danger posed by the giant African snail that has gained entrance into this country without a passport. This snail apparently plays an important part in the transmission cycle of an infectious agent that causes meningitis in humans.

This giant gastropod would pose a threat to agricultural products if it gains a foothold in the United States. Much-needed crops are devastated in parts of Africa, where this animal is abundant.

In other parts of the world, snails play an important role in the transmission of human illnesses by acting as the intermediate hosts of parasitic worms. The most important of these ailments is called snail fever, or by the technical name of Schistosomiasis.

A worm-like fluke that inhabits the human blood stream and establishes residence in important organs of the body causes snail fever. It is prevalent in many parts of Africa, the Far East, and in parts of South America and the Caribbean, including Puerto Rico. The World Health Organization reports that in some areas of Africa and the Far East, up to 70 percent of the population are infected with this serious malady. Blood flukes have been found in ancient Egyptian mummies.

Snails act as necessary intermediate hosts for the Chinese liver fluke, Oriental lung fluke, and intestinal fluke, to name a few of the important human parasitic infections in which snails play an important part in the epidemiology.

Many of us have heard of a condition known as “swimmer’s itch,” and some may have experienced this annoying condition. At certain times, people entering portions of the Great Lakes for a swim will experience a mild to rather severe irritation of the skin. This is caused by the immature stages of a fluke, which is closely related to the one causing snail fever. They burrow into our skin but are unable to penetrate beyond the outer layer, as a response from our immune system kills them off before they can reach a blood vessel. Snails play an important part in the life cycles of the flukes causing this condition.

There are some snails living in the ocean that have a poisonous bite, and there have been several established instances of death that have resulted from contact with them. The snails involved are called cone shells, and are marine. They are to be found in waters around the Hawaiian Islands, New Guinea, Samoa, Australia, and adjacent areas. Collectors prize some of the shells, and care must be taken when handling them.

The oyster drill inhabits our Atlantic and Gulf coasts and is a major predator of oysters. This rather small snail possesses a sharp, rasp-like tongue with which it drills through the shell of an oyster or clam. It then squirts digestive enzymes into the body cavity of the hapless bivalve and proceeds to suck out the partially digested oyster. Oyster drills literally dine on oysters on the “whole shell” and may devastate an oyster bed.

Most snails are neither directly harmful nor beneficial to man. Only a few are detrimental to man, and fewer still are of direct benefit.

Land snails feed on dead plant and animal matter, and act as valuable natural scavengers. And we must not forget their culinary value. In parts of Europe, especially France and Spain, the escargot and caracol are relished. When I lived in France, my neighbor would make periodic forays into the fields to collect large, edible snails. He would then place them in a container filled with flour and allow the mollusks to feed for a week or so. The grass and weeds they had been feeding on would be eliminated from the body and replaced with flour. Only then would he proceed to prepare them for the table. In my opinion, it is hard to beat baked escargots floating in garlic-butter in the shell for an appetizer.

The person who first connected Cupid and his arrows with lovemaking must have known of the mating habits of certain land snails. Two snails with reproduction in mind approach each other and shoot a silvery substance at the prospective mate. This substance penetrates the tissues of the snails and presumably gets them in the right frame of mind to complete the mating process. In any event, the two snails find each other to be irresistible after the “love darts” find their mark.

Dr. Robert Hedeen is a former resident of Maryland’s eastern shore and resided in the Chicago area from 1960 to 1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.

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