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Welcome to our page on cnidarians. We have studied these different species over the past few months and have traveled to many different sites and found out a lot about the different species in the cnidarian group. We have chosen some specific species to study, the glass anemone and the Portuguese man o’ war. We have a wide variety of information to suit your needs. A few facts that we think might be helpful for your safety: The number one group that should never touch would be the jelly group unless you wear protective gloves because they have sting that will harmfully hurt you. Never touch them. Sea anemones can sting too, but the ones that live in the intertidal can sting, but at their maximum size they are too small to hurt. By law, you cannot take coral, so do not remove them, dead or alive, from the environment. Corals are very important to our ecosystem because they provide habitat for many animals. Most of our findings were the glass anemone, Aiptaisia pulchella, which is very abundant in Hawaii, but we found many other various anemones and corals at our site.
The cnidarian group is divided into four classes: Anthozoa, Scyphozoa, Cubozoa, and Hydrozoa. Cnidarians’ special unique feature is their nematocysts. Nematocysts are stinging cells that cnidarians use to protect themselves, as well as for catching their prey. The cnidarians don’t have a digestive system. The food goes into a cavity and then circulates through the body, supplying them with nutrition. They don’t have an anus, and reproduce asexually and sexually by releasing sperm into the water where it by chance connects with eggs, creating a zygote. They do fission, which is when an anemone divides in half and creates two anemones. Cnidarians have two common forms, medusae and polyps. Medusae are free floating and their tentacles face down. Polyps attach onto a surface and their tentacles face upward. Cnidarians that live in colonies like coral have zooxanthellae, which is an organism that photosynthesizes and provides nutrients for the coral. Cnidarians lack internal organs and don’t have a respiratory or circulatory system either. They have radial symmetry. The most dangerous jellyfish is the Australian box jellyfish or seawasp, which can kill a person in minutes, with a sting more toxic than cobra venom. There are many cnidarians in the intertidal. The most common would be the Anthopleura nigrescens (dusky anemones) and Aiptasia pulchella (glass anemones). We also found some rice coral and a Vellella vellella (aka “by the wind sailor”). Species that belong in the cnidarian phylum vary a lot in physical features, but as long as they have nematocysts, they’re considered a cnidarian.
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