What do you think is the weirdest animal that lives in your yard? Perhaps it is a spider, millipede, scorpion, or beetle. Then again, it may be a land planarian. Among the other names given this bizarre critter are soil planarian and arrowhead flatworm.
Once you spot a land planarian, you can readily see why these critters are often mistaken for snakes. They are shaped like a snake, have triangular heads, display broad dark lines that run down the length of their bodies, and can grow upwards of ten inches long. However, if you examine them closely you will see they are covered with mucous, don’t have any eyes and are not covered in scales.
The land planarian’s mouth is located about half way down the underside of its body. Instead of eyes, this animal has eyespots that can only detect light.
The body is covered with a heavy layer of mucous. This mucous enables the flatworm to keep its body moist. A flatworm will die if it loses water that amounts to more than 45 percent of its body weight. As such, land planarians live in cool, moist spots such as under logs, rocks, and forest litter. Around our homes, we most often find them under potted plants, or beneath objects stored on the ground like tarps and lumber. Other than that, we occasionally see them on the surface of the ground when heavy rain saturates the soil.
The land planarian eats a variety of invertebrates such as insect larvae, slugs, and earthworms. While gardeners appreciate the fact they destroy plant pests, they don’t like them eating earthworms as they help aerate the soil. In addition, anglers trying to keep a worm bed or folks that raise earthworms commercially hate them because they have been known to wipe out earthworm populations.
Oh, by the way, if they cannot find enough prey, they will cannibalize one another.
This flatworm feeds by restraining its prey with a coat of slimy mucous. Once it is subdued, the planarian extends its pharynx out of its mouth and into its victim and sucks out its body fluids.
This odd critter employs two forms of reproduction. It can lay eggs in a small cocoon (the eggs hatch in 21 days); however, it primarily multiplies by the process of fragmentation. The process takes place once or twice a month.
Fragmentation occurs when a planarian attaches the tip of its tail to an object and simply pulls away. Remarkably, the detached piece of tail is capable of moving about and will actually grow a new head within only 10 days!
The planarian’s amazing ability to regenerate has long been of interest to biology students and medical researchers alike. Unbelievably, a piece of a planarian, amounting to as little as 1/279th of its body, is capable of regenerating a totally new planarian in a matter of weeks. You can cut a planarian’s head and half and the animal goes about its business sporting two complete heads.
Years ago, planarians were carried to the International Space Station to determine what effects, if any, the environment has on such things as their power of regeneration. In one experiment, after an astronaut sliced a planarian’s head in half, the animal regenerated two heads in only five weeks time.
Planarians are currently being employed by researchers involved in biomedical research studies focus everything from human aging, memory, and diseases to genetics.
You can add the ground planarian to the list of exotic plants and animals that have been inadvertently brought to the United States. In this case, it is believed this native of Indo-China they were shipped around the world during the 19th century hidden in soil accompanying nursery stock.
Since the beginning to the 20th century, the flatworm has been located living in greenhouses across the country. It has since been found in Georgia, Florida, Alabama, North and South Carolina, Tennessee and a number of other states. It is thought the worms were introduced to these locations in potted plants sold in the nursery trade.
While it is clear we could easily live without this critter, like it or not, there is little chance we will ever rid ourselves of the odd introduced animal. In the meantime, countless folks will continue to be shocked when they lift up a pot and see what looks like a bunch of baby poisonous snakes poised to strike. Just remember, if these weird animals are slimy and lack eyes, they will not bite.