| Tuesday, September 26, 2000 3:38 PM |
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Luann, I will forward some info to you about jellyfish. I have read studies that they affect the plankton communities. . .but I am not sure how that would affect your pond. It is always hard to predict such introductions. I would like to hear how it turns out though!!! Thank you for your email & reporting the jellyfish sighting. I'm a graduate student working with Dr. Terry Peard at Indiana University of Pennsylvania. We're currently looking at the molecular differences between freshwater jellyfish collected throughout the world. It would be very interesting to see how similar and/or different your specimens are, compared to those here in Pennsylvania. Would you have access to a digital camera or have any way of sending a digital image (email attachment) of these specimens? Also, if you're willing to send samples (when you find any) to our lab, I would be most thankful. Simply place the medusae in a small, screw-cap jar with 70% Alcohol [Isopropyl 'rubbing' alcohol (or) Ethyl alcohol]. Make sure the alcohol fills the jar. Wrap tape around the lid and secure the jar with foam or padding (it will have a bumpy ride along the way). Please send to : [address removed] Indiana Univ. of Pennsylvania Indiana, PA 15701 For your enjoyment, I've included some general jellyfish information... Here is a diagram of a typical jellyfish medusa. Jellyfish do NOT have a brain, nor eyes. Their nervous system is more primitive than other organisms. The bell margin contains two types of sensory structures - ocelli and statocysts. The ocelli consist of patches of pigment and photoreceptor cells. Some jellyfish are postively phototactic and move towards light while other jellyfish are negatively phototactic and move away from light. Others show no phototaxis. The statocyst consists of a vesicle or pit containing a calcium sulfate concretion and sensory cilia. Tilting of the jellyfish causes the concretion to contact and stimulate the sensory cilia. Statocyst stimulation appears to inhibit muscle movement on that side of the bell, and the opposite side contracts to right the jellyfish. Jellyfish do NOT breath nor do they have gills, but they must obtain oxygen from their environment. Jellyfish have a stomach called a gastrovascular cavity. Both food and water enter through the mouth and into the gastrovascular cavity. From the stomach, broken down food and water move through radial canals and into the ring canal (the outer edge of the bell). Oxygen in the water passing through the gastrovascular system can diffuse into the cells of the jellyfish. Difussion of oxygen takes place from the water moving through the gastrovascular system as well from the water surrounding the jellyfish. Jellyfish "Schyphozoa", Coral, Sea Anemone's, Hydra, etc are all closely related, phylogenetically. They are all in the PHYLUM CNIDARIA. MARINE Jellyfish are in a CLASS called "SCHYPHOZOA"... All CNIDARIANS have stinging cells. At IUP, we study a jellyfish from the CLASS HYDROZOA. Here is some information about the FRESHWATER jellyfish, Craspedacusta sowerbii, that we study: Kingdom - Animalia phylum - Cnidaria class - Hydrozoa order - Trachylina family - Olinidae genus - Craspedacusta species - sowerbii Craspedacusta sowerbii was first described in 1880 in a water lily tank at Regent's Park in London (Lankester 1880). The origin of this species is thought to have occurred in East Asia in the Yangtze River Valley of China (Kramp 1951). Pennsylvania's initial records began in 1885 in Philadelphia (Potts 1897; Dexter 1949). A tiny, stalked form of the jellyfish (the polyp) lives as colonies attached to stable underwater surfaces such as rooted plants, rocks, or tree stumps. The microscopic polyp colonies feed and reproduce during the spring and summer months. The polyps reproduce asexually. Some of their offspring are the jellyfish that can be seen at the surface. The "jellyfish" or medusa reproduce sexually. Fertilized eggs develop into planula larvae which eventually settle to the bottom of the pond or lake and develop into polyps. However, in the United States, most populations of jellyfish are either all male or all female, so sexual reproduction may be rare. The appearance of the jellyfish is described as sporadic and unpredictable. Often, jellyfish will appear in a body of water in large numbers even though they were never reported there before. The following year they may be absent and may not reappear until several years later. It is also possible for the jellyfish to appear once and never appear in that body of water again. During the winter, the polyps contract and become "resting bodies" that are capable of surviving the cold temperatures. Some scientists believe that the resting bodies, called podocysts, are one way in which the jellyfish are transported from lake to lake. It is believed that the podocysts may be transported on aquatic plants, by aquatic animals, or perhaps on the feet of birds. When conditions become favorable, the podocysts develop into polyps, and the life cycle is continued. Our jellyfish (medusae) cannot be successfully maintained for an extended period of time in an aquarium. Fully mature medusae can grow to the size of a quarter. I have experience culturing the polyps and have made several attempts to raise medusae to maturity. They only live for 1 1/2 weeks in a standard 10 gal fish tank. We can't maintain collected medusae (July to September) for more than 2 1/2 weeks. We feed them live brine shrimp, Daphnia, copepods, etc... No luck. C. sowerbii jellyfish eat tiny, microscopic animals called zooplankton that are found suspended throughout the water. The following pictures might help you visualize their feeding mechanisms: (I've attached a picture of an immature medusa stage and one of a polyp stage.) The attached polyps (on a substrate) will sting zooplankton that swim into their stinging cells, located at the 'mouth-region'. The zooplankton will actually 'stick' to the jellyfish. From there, the food is ingested into a 'gastrovascular cavity' or stomach and later digested. The medusa (freely swimming) will sting zooplankton that swim into their stinging cells, located on the tentacles, but also sting zooplankton that the jellyfish, themselves, swim into. The tentacles help move the prey toward the medusa's manubrium "mouth". You can see the manubrium hanging from the top-portion of the immature medusa. From there, the food is taken into the gastrovascular cavity and digested with enzymes. Hope this helps. Thanks again for your email! -- Tony ========================================== Graduate Assistant, IUP Teacher Education Center M.S. Biology Candidate Indiana University of Pennsylvania http://www.iup.edu/~tpeard/jellyfish.htmlx ========================================== |
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