Jul
23

These slimy invaders need to escargot back where they came from

One of 67 live African giant snails intercepted July 1, at Los Angeles International Airport in a shipment from Nigeria. (Greg Bartman, United States Department of Agriculture)

One of 67 live African giant snails intercepted July 1, at Los Angeles International Airport in a shipment from Nigeria. (Photo by Greg Bartman, United States Department of Agriculture)

It’s related to one of the world’s most destructive invasive species, and possibly the slimiest. Thirty-five pounds of live giant West African snails (Archachatina marginata) were confiscated this month by U.S. Customs and Border Patrol agents at the Los Angeles Airport from importers who were shipping the mollusks from Nigeria to San Dimas, Calif., to be used as food. Some aquaria hobbyists also prize the snails as pets. While U.S. Customs agents may have successfully stopped these snails from entering California, the giant East Africa nail (Archachatina fulica) is already well established across the Hawaiian Islands and Florida is fighting a second invasion of the mollusks. It took 10 years for Florida to eradicate a first invasion of the destructive African snails after they were discovered in the state in the 1960s.

Ellen Strong, curator of mollusks at the Smithsonian’s National Museum of Natural History, sat down with Smithsonian Science and tells us everything we need to know about African giant snails.

Should we be scared?

Not unless you eat these snails raw or undercooked. African giant snails carry a parasitic nematode that can be a vector for meningitis in humans. The snail acts as an intermediate host between the parasite and its natural final host in rodents.

Have you ever eaten one?

I have not eaten them. I have eaten other kinds of snails but not African giant snails.

Is it safe to say that one snail species tastes pretty much like another?

Among the African peoples who have a tradition of eating achatinid snails, the two species preferred are the giant West African snail (A. marginata) and the giant African snail (A. achatina). The giant East African snail (A. fulica), the most destructive of these species, is not considered a desireable food species. Different snail species probably taste slightly different; some are more muscular than others so they will have a different texture or may be more or less rubbery. A lot depends on how you prepare them. Lots of snails are used for food. That is one of the ways they are introduced to new countries.

As a public service, here is a demonstration of a traditional method of preparing African giant snails.

Okay, so we can eat them. What do they eat?

Giant East African snails are te most destructive and they eat hundreds of different kinds of plants so they are a huge pest of agricultural crops. Voracious and large they can eat and eat and they are not very selective. This is the main reason giant East African giant snails are on the list of the top 100 invasive organisms prohibited in the United States. They have even been known to damage stucco by grazing on it. I’m not sure what it is about stucco that appeals to them, but it is probably the lime as a source of calcium. Calcium is a limiting nutrient for many land snail species.

Do they have any other natural predators?

Not many. In their natural range in Africa, they are eaten by birds, cats and of course humans. Most things that eat them feed on the young and before they get large and slimy. They produce large quantities of mucus, which can be a deterrent to predators. One animal that will eat their eggs and young is another snail, called the rosy wolfsnail (Euglandina rosea), a native of tropical North America which is a specialized snail-eating snail. This snail was purposely introduced to Hawaii and other Pacific Islands to try and control introduced populations of the African giant snail. Instead it set its sights on native species of land snails and has ended up being a big problem for the native land snails of Hawaii, eating them rather than its intended target. The rosy wolfsnail has caused the extinction of numerous native species of snails.

Why did it take so long for Florida to eradicate the first invasion?

As with other land snails, each giant East African snail has both male and female reproductive parts, and it only takes one gravid snail to lay hundreds of eggs and establish a new population in a short time. Each giant snail can live as long as nine years, with some living more than 10 years. It has also become established on islands of the Caribbean and the Pacific.


Posted: 23 July 2014
About the Author:

John Barrat is the editor of Smithsonian Science (http://smithsonianscience.org/), a web site featuring highlights of the Smithsonian Institution’s scientific research in the fields of anthropology, astrophysics, conservation biology, geology and more.