Wild Guide

Freshwater Jellyfish | Craspedacusta sowerbyii

Status

Commonly encountered in Missouri but sporadic during medusa stage

Size

½ to 1 inch

Distribution

Statewide

Freshwater jellyfish are typically found in calm or standing water in ponds, lakes, reservoirs, and quiet or sluggish pools. They usually float just below the surface and when they appear are often seen in great numbers. They swim by pulsating contractions of their umbrellalike body. Jellies are transparent or translucent, sometimes tinted tan, gray, white, green, or blue.

Life Cycle

Freshwater jellyfish have two phases — polyp and medusa. During the polyp phase, the jellyfish reproduces asexually by “budding.” A bud forms on the side of the polyp, grows, and breaks away as a new polyp. However, it can break away as a medusa. In this phase, it can create sperm and eggs and can reproduce sexually.

Foods

Freshwater jellyfish prey on any tiny animals, but zooplankton are a favorite. The medusae wave their tentacles slowly in the water, using special stinging cells to subdue its prey. The tentacles draw the food into the jellyfish’s mouth.

Ecosystems

Tiny plants and animals form the base of the food chain. Freshwater jellies are an important link between the tiny animals they eat and their own predators, including crayfish.

Did You Know?

Freshwater jellies are similar to their saltwater cousins. Their tentacles do have the same stinging cells, used for feeding, but they probably cannot penetrate human skin.