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As the water warms, the polyp begins to double itself over and over, resembling a stack of saucers. During this process, known as strobilization, a tiny medusa is formed (ephrya). The ephrya wriggles free from the polyp and finds a home in smaller creeks.


Strangely enough, the life cycle of the stinging nettle includes two very different body forms as well as a sexual stage and an asexual stage. This phenomenon is known as “alternation of generations.” By early summer, the ephryae migrate into the open waters of the Bay to feed on plankton. The more they food they consume, the more they will grow throughout their lives.


Chrysaora quinquecirrha Life Cycle


Where do stinging nettles go in the fall? Once they have spawned in mid-late summer, they die. Fertilization occurs when the male releases sperm into the water (broadcast spawning). Once the sperm enters the stomach cavity of the


female, the egg is fertilized and a tiny planula larva forms. The pinhead sized larva drifts along with other plankton before sinking to the bottom, cementing itself to a hard surface, such as an oyster shell or a rock. The larva then becomes a polyp, a hollow cylinder with a mouth and tentacles at the top.


Jellyfish Forecast


What conditions are ideal for jellyfish? Warm water temperatures combined with dry conditions and an abundance of food, are factors that contribute to the growth of jellyfish. Able to survive in waters of lower salinity (10–16ppt), but not fresh water, stinging nettles are more prevalent in the Bay and its rivers when temperatures range between 78–86 degrees. Recently, scientists developed an experimental model for predicting nettles. By taking satellite images and gathering salinity and water temperature readings, real-time maps are created showing probable areas for nettles along the East Coast. Before taking a dip in the river, you can refer to a map of nettle distribution for your region on NOAA’s Chesapeake Bay Office website: www. chesapeakebay.noaa.gov.


Treating a Jellyfish Sting


The severity of a jellyfish sting varies with the species, and the sting of the Chrysaora is considered moderate to severe. The stinging sensation differs from person to person depending on the location of the sting and the person’s sensitivity to the venom. When we get stung it is likely that the jellyfish thinks of us as a meal swimming into its tentacles. Dr. Deborah Steinberg professor at VA Institute of Marine Science notes, “It is not clear how much stinging is used as a defense, as this is very hard to distinguish from prey capture.” Should you get zapped by a stinging nettle, there are a few steps you should


26 July/August 2011


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