Freshwater Jellyfish
Zoologists call them Craspedacusta sowerbyi, but more commonly they are referred to as freshwater jellyfish, or medusa. The jellyfish is an invertebrate, or an "animal without a backbone," and belongs to a group called Coelenterata, which includes animals having a sac-like digestive tract and tentacles with stinging cells. Nearly all jellyfish are saltwater species, and the ones shown here are the only freshwater forms in North America.
The freshwater jellyfish is very small, measuring about the size of a dime to the size of a quarter. The outer edge of its bell or hood bears several hundred tentacles of different lengths and sizes. These are used by the jellyfish in capturing its food, which is mostly small plankton organisms. These tiny organisms are entangled in the tentacles and paralyzed by the stinging cells.
When temperature and water conditions are just right, these jellyfish can be found in large numbers. They are moved by the wave action of the water and by their own rather feeble swimming movements. The activity of the jellyfish is an up and down swimming motion by the contraction and expansion of the bell-like hood.
These photos, of jellyfish found in Stuart Lake, were taken August 16. - Photos by Diane Graves.
The freshwater jellyfish is very small, measuring about the size of a dime to the size of a quarter. The outer edge of its bell or hood bears several hundred tentacles of different lengths and sizes. These are used by the jellyfish in capturing its food, which is mostly small plankton organisms. These tiny organisms are entangled in the tentacles and paralyzed by the stinging cells.
When temperature and water conditions are just right, these jellyfish can be found in large numbers. They are moved by the wave action of the water and by their own rather feeble swimming movements. The activity of the jellyfish is an up and down swimming motion by the contraction and expansion of the bell-like hood.
These photos, of jellyfish found in Stuart Lake, were taken August 16. - Photos by Diane Graves.
