Featured Creatures

Take a Closer Look at the Colorful Marine Flatworms

Planarians are free-living flatworms. Like other flatworms the planarian has a bilateral body plan with a brain and stereo eyes that enable it to actively hunt. Unlike the flashy flatworms that live in the ocean, the thousands of species of planarians live either in freshwater or on land around the world.

Marine flatworms can dazzle with wild colors and patterns – if you’re lucky enough to see one. They live from the intertidal to tropical coral reefs to deep water. The free-living flatworms (polyclads) have thin, almost leaf-like bodies and move with a gliding motion. Their ancestors were  some of the first bilateral animals, and being bilateral gives them a body plan designed for an active life style.At Shape of Life, we call the flatworm phyla video "First Hunter," and indeed these animals are active carnivorous predators that feed on a wide variety of animals including copepods, isopods, limpets, barnacles, tunicates, and bryozoans.

Many species of flatworms live in marine environments. They are simultaneous hermaphrodites, meaning they are both male and female. It's advantageous to be a hermaphrodite since the odds of successful reproduction are doubled. What’s the strategy for reproducing if you’re both male and female? It’s complicated. When a pair of flatworms of the same species meets, each can deliver sperm or receive it for fertilizing eggs internally. There’s a natural conflict since it takes a lot of energy to grow and carry fertilized eggs, so each animal wants to be the male.

We typically think of flatworms as being pretty easy going. Not this one. The New Guinea flatworm, is a powerful predator that feeds on other worms, snails and a variety of soil-dwelling creatures. Flatworms come in many varieties, sizes and lifestyles. There are over 20,000 identified species both free-living and parasitic.The New Guinea flatworm, a land planarian, is in the news since it made “The 100 Worst Invasive Species” list by International Union for Conservation of Nature (IUCN). It is spreading to many corners of the world, gobbling up prey as it goes. Now, the two-inch long flatworm has made it to the continental United States. So what’s the problem with having this invasive flatworm on our shores? It likely has no natural predators, which means it could wreak havoc on soil ecosystems rippling up the food chain to animals, like birds, that feed on earthworms and snails.Read More:From IFL Science! New Guinea Flatworm, one of the Worst Known Invasive Species, Found in USFrom Science Daily Discovery in the US of the New Guinea flatworm, one of the worst known invasive speciesVideo: Highly Invasive Snail-Eating Flatworm Species Spotted In U.S.Watch the Shape of Life Flatworm video: Flatworms: The First Hunter