Jellyfish
Jellyfish belong to the phylum Cnidaria, whose members possess stinging cells that can inject a paralyzing poison into prey. Other members of this phylum include sea anemones, sea fans, hydra and reef-forming corals. True jellyfish fit into the speciesscyphozoa; most have an umbrella shaped concave body with a centrally located mouth. The cells that line the inner part of the jellyfish body cavity secrete digestive enzymes and absorb nutrients. The fossil record for cnidarians begins in the Pre-Cambrian (earliest) era of earth history, meaning that the direct ancestry of these creatures dates to at least 600 million years ago!
Big Red! In the depths of the ocean lurks a huge, predatory jellyfish, recently caught in the Monterey Submarine Canyon (a 4000-meter trench off of the California coast). The dark red creatures are 2 to 3 feet long, and roam waters that rarely get above 40 degrees Fahrenheit. Most surprisingly, in place of tentacles, they have a few short, thick arms that may be used for feeding. Though Big Red had been discovered and photographed a few years ago, scientists only recently obtained a specimen for study. They currently know almost nothing about it, but hope to learn more in the coming months. Get the details and photos at National Geographic.
These jellyfish can see, man. The box jellyfish, known for their square-shaped bodies, are more sophisticated than most jellyfish species. Not only can they swim better, but recently scientists discovered that 8 of their 24 eyes function extremely well. Each eye contains a lens and a retina, providing a blurred vision that allows the animal to focus on large objects. This form of vision works well in the near shore waters, among mangrove roots and other obstacles, that box jellyfish populate. Read more at Science News.
Killer Jellyfish. Okay, so not only can box jellyfish see, but one species is tailor-made to attack and kill vertebrates. The box jelly Chironex fleckeri, found off the coast of northern Australia, has perhaps the most deadly venom in the word. Sixty-five Australians have been killed by it in the last 50 years. While many jellyfish species float freely and feed on plankton, these predators swim fast and can kill fish and other animals with “a single flick of a tentacle”. Their tentacles can grow to nearly seven feet long, so they are a definite danger to swimmers. More from Natural History magazine.
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