Flatworms are wee creatures of the phylum Platyhelminthes. Roughly 20,000 species of these worms are thought to exist around the world. Flatworms' physiques are smooth in texture and markedly flat. Although the majority of them are parasitic, residing within other organisms, some also inhabit aquatic environments, where they are susceptible to predation.
Basic Facts on Flatworms
Flatworms' bodies are not segmented. They have heads and central nervous systems. However, they are devoid of circulatory or respiratory systems. Both asexual and sexual breeding are possible for the bulk of flatworm species. The largest fraction of flatworms are hermaphroditic or monoecious. The flatworm phylum has four distinct classes, Monogenea, Turbellaria, Cestoda and Trematoda. Turbellaria flatworms are the sole nonparasitic species.
Things That Eat Flatworms
Predators have access to free-roaming flatworms from the class Turbellaria -- after all, they're in no way confined to the bodies of animals. These flatworms live in many types of settings, including streams, creeks, lakes and ponds. Extremely damp environments are an absolute must for them. They tend to hang out below stones or in piles of foliage. Water bugs are one example of the diverse predators of these flatworms -- specifically diving beetles and youngsters of dragonflies. Crustaceans, tiny fishes and tadpole also routinely dine on these kinds of flatworms.
Flatworms in Reef Tanks
If you have a reef tank and are noticing the sudden presence of pesky flatworms, they could be invading your marine corals. Some aquarium owners opt to use certain types of fish for biological management of flatworms. Examples of specific fish who often enthusiastically eat flatworms are six-line wrasses (Pseudocheilinus hexataenia), yellow wrasses (Halichoeres chrysus) and spotted mandarins (Synchiropus picturatus).
Flatworms as Predators
Many flatworms are indeed the parasites of unwitting hosts, but a few of them also are true predators. Marine flatworms are for the most part carnivores. Tiny invertebrates are a particular meal favorite for them, including worms, crustaceans and rotifers. Scavenging also is a pastime for these flatworms, as they also occasionally consume carrion -- the remnants of dead creatures dropped down to the seafloor. Dead snails and algae also make up part of the flatworm diet. Once in a while, they dine on fellow flatworms, including those of their exact same species. Although nonparasitic flatworms might not look too intimidating, they aren't too shabby as predators. Many of these guys are less than 0.25 inch in length, and it's highly uncommon for them to ever exceed an inch. Their talent as predators may be a result of their strong senses, according to the website for the Missouri Department of Conservation.
- University of California Museum of Paleontology: Introduction to the Platyhelminthes
- Fairfax County Public Schools: Flatworm
- Missouri Department of Conservation: Turbellarians
- Animal Planet: Flatworm
- University of Michigan Animal Diversity Web: Platyhelminthes
- Fulton-Montgomery Community College: Flatworm Characteristics
- ReefED: Flatworms