Terry Woods's video: Jellyfish Invade San Joaquin

The freshwater "jellyfish" is not a true jellyfish as are some of its marine relatives. Freshwater "jellyfish" differ slightly from the true marine jellyfish. Craspedacusta sowerbii (kras-ped-uh-kus-tuh) is the scientific name of this freshwater "jellyfish". One obvious difference is that unlike marine jellyfish, C. sowerbii has a structure called a velum on the ventral surface. This thin, shelf-like membranous structure extends inward from the circular edge (ring canal) of the bell. The manubrium, which ends in a mouth, extends down through a hole in the velum. The velum helps set C. sowerbii apart from the true jellyfish. However, because C. sowerbii looks like a jellyfish, we call it a jellyfish! Usually late summer. August and September are peak months for jellyfish sightings in Pennsylvania when lake water is warm and food is abundant. The jellyfish will be floating or swimming gently just below the surface of the water. They are easily seen by the naked eye. They often surface in large numbers called "blooms". Sunny days are especially good for spotting jellyfish.It depends. Like true jellyfish, they do have stinging cells (cnidocytes). This mechanism is designed for feeding, as the cnidocytes are utilized to paralyze macroinvertebrates and even small fish. However, we have no "hard" evidence that these organisms can penetrate human skin (though some have claimed otherwise). 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. We will meet the fisherman at the spot and Jeff shot an interview with FSU Prof about them.. They have been found here before, see info from freshwaterjellyfish.org Bass Lake, Madera County, near Road 274 (2006) Bass Lake, near Bass Lake, Madera County, near 222 (2006) Bass Lake, near Oakhurst, Madera County, near Hwy 41 (2003, 2006) Bass Lake, near Oakhurst, Madera County, near Hwy 222 (2006) Bass Lake, near Pines Village, Madera County (2003) Blackhawk Lake, near Coarsegold, Madera County, near Hwy 41 (2006) Fresno County Sportsmen's Club pond, Fresno, Fresno County, Friant Road/Rice Road (2004, 2007) Pond, private, Sanger, Fresno County, Bethel Avenue (2007) San Joaquin River, near Fresno/Madera, Fresno/Madera Counties, Ave. 7 and Rd. 35. (2004)