- Aquatic Biomes
- lakes and ponds
- rivers and streams
This organism shares many of the same traits characteristic of most jellyfish. It is a white or green gelatinous creature, with 99% of its body made of water (Peard, 2000). This organism lacks a head, a skeleton, contains no special organs for respiration or excretion (Davis, 1998).
The freshwater jellyfish is dimorphic, alternating between both a polyp and medusa morph (Johnson and Raven, 1999). The mature medusa stage resembles a bell shape. It also contains the manubrium, four radial canals, and one circular canal, typical of most jellyfish.
The diameter of the circular canal is anywhere from 5 to 22mm. It bears string-like tentacles, arranged in sets of three to seven. The tentacles are solid and vary in length. Tentacles, with nematocysts, aid in capturing food and serve as a type of protection against predation. At the base of their tentacles, jellyfish have eyespots. These are used in detecting light and dark, providing another means by which to find food and escape predation.
This organism can move in any direction by pulsating contractions along its bell surface. The bell margin is made up of statocysts while the velum is made of nematocysts, which are in abundance around the mouth. This is helpful when the jellyfish is killing its prey, helping to draw the prey into the jellyfish's mouth (Pennak 1989). (Johnson and Raven, 1999; Peard, 2000; Pennak, 1989)
- Range mass
- 3 to 5 g
- 0.11 to 0.18 oz
reproduce asexually in the polyp form, via budding. They can form three different types of buds: polyps, frustules, or medusa buds. The polyp bud grows and develops while still attached to the original polyp. The frustule bud develops into a frustule; they are only able to travel a short distance before developing into a new polyp. The medusa bud detaches to form a free-living adult medusa, which reproduces sexually via fertilized eggs, which develop into planula larva. These larva settle onto underwater surfaces (plant roots, rocks, and tree roots) where they develop into polyps (Peard 2000).
Sexual reproduction is relatively rare in this form of jellyfish. Most populations are strictly male or female (Peard, 2000).
Scientists are still learning about the larvae and the conditions affecting the dispersal of this organism. Correlation studies have demonstrated a relationship between increased travel distance of the larvae and increased polyp feeding. It is believed that increased polyp feeding increases the energy stores of the frustules, allowing them to travel greater distances (Peard 2000).
The polyps can be distributed passively as well. During winter months, polyps contract and become dormant, as to survive the cold temperatures. These polyps, also known as podocysts, can be transported by aquatic plants, aquatic animals, or birds' feet to new areas of dispersal. As winter ends, and conditions become more favorable, the podocysts transform into polyps (Peard 2000). (Peard, 2000)
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- broadcast (group) spawning
- Parental Investment
- no parental involvement
Freshwater jellyfish can be spotted during the summer and fall months, with August and September being peak months. Warm water temperatures and an abundance of food cause a proliferation of this species (Peard 2000).
Jellyfish tend to lie on the bottom of shallow waters; they generally conserve their energy for efforts of capturing food or escaping predation (Pennak 1989).
The diet of the freshwater jellyfish consists primarily of zooplankton, which range in size from 0.2 to 2.0 mm in size. It uses its nematocysts located on tentacles to sting and paralyze prey before scooping it into its mouth (Pennak, 1989).
Freshwater jellyfish are unpredictable in their appearance within bodies of water. They may appear in large numbers one year, not appear the next, and come back several years later (Peard 2000). Thus, populations are difficult to predict.
possess cnidocytes with nematocysts, otherwise known as stinging cells. Unlike some other jellyfish, the nematocysts of freshwater jellyfish are unable to penetrate human skin (Peard 2000). Therefore, freshwater jellyfish are unable to produce the painful sting caused by most marine jellyfish.
Freshwater jellyfish are hard to raise in an aquarium. If you choose to try raising one, here are some things to keep in mind: 1) make sure that you have a filtration system that will not suck up the jellyfish (sponge filters are not recommended); 2) do not use a tank that has a strong current; 3) jellyfish can kill small fish with their stinging cells; 4) jellyfish require a constant supply of food (brine shrimp or Daphnia are suggested) (Peard 2000).
Information about (Peard, 2000)is incomplete. Researchers continue to study this organism. Indiana University of Pennsylvania is currently involved in an in-depth study of this creature (Peard 2000).
Autumn Erwin (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
found in the oriental region of the world. In other words, India and southeast Asia.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- radial symmetry
a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).
- seasonal breeding
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).
Davis, A. 1998. "Smithsonian Environmental Research Center" (On-line). Accessed February 16,2000 at http://www.serc.si.edu.
Johnson, G., P. Raven. 1999. Biology, 5th Ed. U.S.A: The McGraw Hill Companies, Inc..
Kottak, C. 2000. Anthropology: The Exploration of Human Diversity. USA: The McGraw-Hill Companies, Inc.
Peard, T. 2000. "Freshwater Jellyfish" (On-line). Accessed February 26, 2000 at http://www.jellyfish.iup.edu/.
Pennak, R. 1989. Fresh-Water Invertebrates of the United States: Protozoa to Mollusca, 3rd Ed.. New York, USA: A Wiley-Interscience Publication.