14 Land planarian

first_imgVolume XXXINumber 1Page 14 From time to time, someone somewhere in Georgia turns over a rockor log and finds a grayish brown, flat worm with a head shapedlike a half-moon. It’s one of those things that, when you findit, you just have to find out what it is. It’s called a land planarian.You rarely see these curious creatures. Originating in Asia,they’ve traveled around the world in nursery pots, arriving inNorth America a century ago. They’re typically found neargreenhouses. If the habitat is warm and moist enough, they canescape and get established in the wild.Land planarians are in a primitive group of worms called, aptlyenough, flatworms. They don’t have circulatory, respiratory orskeletal systems.Spatula headsTheir semicircular heads look like little spatulas. In some partsof the world, they’re called “shovel-headed garden worms.” Whilethe top is typically gray to greenish-brown with darker stripes,the underside is pale.They don’t have eyes. But light-sensitive cells allow them toperceive light, which they shun. Land planarians can easilydesiccate, or dry out, so they have to remain in cool, dampareas. Because they avoid light, they spend the daylight hiding inmoist places under logs or in the soil.Relaxed, a land planarian may be only 3 or 4 inches long. Whenit’s crawling, though, it can easily double this length.Full-grown, it may be 12 inches long.Like snails and slugs, land planarians glide on mucus, secretingslime to help them move. These dried slime trails are signs ofplanarians, although they look exactly like the tracks that slugsor snails leave behind.Really weirdLand planarians lay eggs, but they can also reproduce by budding,or detaching from the tail end a small segment that develops anew head within a week or so.Strangely, the planarian’s mouth isn’t on its head but halfwaydown its belly. It wraps itself around an earthworm, attackingprey up to 10 times its size, and sucks its juices. Even moreoddly, the same opening serves as its anus.Although they’re found around plant nurseries, they’re harmlessto plants. Some land planarians feed on slugs and insect larvae.The most common species in Georgia, though, feeds on earthworms.And yes, they’re cannibalistic, too.These weird worms are rare in Georgia. Gardeners are the peoplemost likely to encounter them, while digging in the soil orturning over rocks and logs.But it’s OK. They’re not known to be poisonous, although there issome evidence they don’t taste good to dogs.Because they’re harmless, there aren’t any controlrecommendations. Science teachers at your local school willprobably be glad to take any specimens you can provide.last_img


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