Critter Catalog

What do they look like?

Flatworms are very small, almost microscopic in size. They are small, flattened worm-like animals. These flatworms have a forked tail in their free-living, cercaria form.

• Other Physical Features
• ectothermic
• bilateral symmetry

Where do they live?

This flatworm species is found throughout North America.

• Biogeographic Regions
• nearctic
  • native

What kind of habitat do they need?

This parasite is found in aquatic habitats. The first hosts are aquatic snails. After maturation, the parasite can be found in the intestine of Belted Kingfishers. They then infect fish, such as rock bass, bass, perch, and sunfish.

• These animals are found in the following types of habitat
• temperate
• freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams

• Wetlands
• swamp

How do they grow?

Eggs are passed in the droppings of kingfishers. When conditions are right, they hatch in the water to form miracidia larvae. These miracidia enter a snail and shed their outer layer. They transform into mother sporocysts, which produce other sporocysts by asexual splitting. These sporocysts attack the snail's liver and digestive glands. After about 6 weeks of infection the sporocysts develop into fork-tailed cercaria. These escape into the water, where they swim and rest for a short time. When ready to invade a fish, a cercaria attaches itself to the fish's skin and bores through it, losing its forked tail in the process. The infection of the fish causes black spots to appear around the cysts. If a fish is heavily infected, a condition known as popeye is caused, in which the fish's eyes bulge out from their sockets. Kingfishers become infected by eating infected fishes.

How do they behave?

• Key Behaviors
• parasite

What do they eat?

This parasite, in its first stages, invades a snail and feeds off of its tissues. At a later stage, it separates from the snail and penetrates a fish, where it takes energy from the fish's tissues. The fish is eaten by a kingfisher, within which the parasite develops through its sexual stage.

What eats them and how do they avoid being eaten?

No animals prey directly on these flatworms, although they may be eaten by filter-feeding aquatic animals during their free-living stage.

What roles do they have in the ecosystem?

These animals are important parasites of fish species, Belted Kingfishers, and aquatic snails. They negatively affect these hosts when they take nutrients from the host's tissues.

Do they cause problems?

These flatworms have a negative effect on the fish populations that they infect. Many of these fish species are economically important to humans.

Are they endangered?

These animals are widespread and abundant.

• IUCN Red List [Link]

  Not Evaluated