Drifting along our shores and into our calendar, it's World Jellyfish Day! Jellyfish can be found in all the world's oceans, in all shapes and sizes. There are about 2,000 species, all lacking hearts, bones, and brains. Pacific sea nettle jellyfish, seen here, have vibrant golden-brown coloring and long tentacles and inhabit the coastal waters of California and Oregon. Moon jellyfish are pale with short tentacles, and, in an appropriate twist, went into orbit aboard the space shuttle Columbia in 1991, to help scientists study their unique biology. Jellyfish play a vital role in the ocean's food chain, as the main food source for many animals, including sea turtles. Their numbers are impacted by climate change, marine pollution, and overfishing, and in turn have reverberating effects on sea life around them.