Jellyfish
Commonly known as anemones, jellyfish or corals, Cnidaria play important ecological roles in food webs. Cnidaria is a phylum containing over 10,000 species of animals found exclusively in aquatic and mostly marine environments. Cnidarians are classified into four main groups: the almost wholly sessile Anthozoa, swimming Scyphozoa or true jellyfish, Cubozoa or box jellies, and Hydrozoa. Their distinguishing feature are the cnidocytes, specialized cells that they use mainly for capturing prey.
Cnidarians have only rudimentary organs. Their bodies consist of mesoglea, a non-living jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick. They have two basic body forms: swimming medusae and sessile polyps, both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes. Cnidarians' activities are coordinated by a decentralized nerve net and simple receptors. Several free-swimming Cubozoa and Scyphozoa possess balance-sensing statocysts, and some have simple eyes and both forms have a single orifice and body cavity that are used for digestion and respiration. Not all cnidarians reproduce sexually. Many have complex lifecycles with asexual polyp stages and sexual medusae, but some omit either the polyp or the medusa stage.
Food is taken into a central gastrovascular cavity, often with branches into the tentacles, where digestions is extracelluar followed by intracellular digestion. The branches of the gastrovascular cavity allow food particles to travel to remote parts of the body and therefore serve a rudimentary circulatory system function. Unused material and waste is released through the mouth. This means that that mouth also serves as an anus. The excreted waste is not feces in the traditional sense, it resembles something closer to urine that is carried away by the current. A nervous system and simple muscle cells allow the animals to move and to react to their environments. Specialized organs for respiration, circulation and excretion however, are lacking. The skeleton may be external as in corals or hydrostatic as in anemones.
Food is taken into a central gastrovascular cavity, often with branches into the tentacles, where digestions is extracelluar followed by intracellular digestion. The branches of the gastrovascular cavity allow food particles to travel to remote parts of the body and therefore serve a rudimentary circulatory system function. Unused material and waste is released through the mouth. This means that that mouth also serves as an anus. The excreted waste is not feces in the traditional sense, it resembles something closer to urine that is carried away by the current. A nervous system and simple muscle cells allow the animals to move and to react to their environments. Specialized organs for respiration, circulation and excretion however, are lacking. The skeleton may be external as in corals or hydrostatic as in anemones.
Chironex fleckeri
The Chironex fleckeri or the sea wasp, is a species of Box jellyfish found in coastal waters from northern Australia and New Guinea north to the Philippines and Vietnam. It has been described as the most lethal jellyfish in the world, with at least 63 known deaths in Australia from 1884 to 1996. Notorious for its sting, C. fleckeri has tentacles up to 3 metres long which are covered in thousands upon thousands of cnidocytes which, on contact, release microscopic darts, each delivering an extremely powerful venom. Being stung commonly results in excruciating pain, and if the sting area is significant, an untreated victim may die in as little as 3 minutes. The amount of venom in one animal is said to be enough to kill 60 adult humans.
Physalia physalis
The Physalia physalis, or Portuguese Man of War is a jelly-like marine invertebrate of the family Physaliidae. Its venomous tentacles can deliver a powerful sting. Despite its outward appearance, the man of war is not a true jellyfish but a siphonophore, which differs from jellyfish in that it is not actually a single creature, but a colonial organism made up of many minute individuals called zooids. Each of these zooids is highly specialized, and, although structurally similar to other solitary animals, they are attached to one another and physiologically integrated to the extent that they are incapable of independent survival. The Physalia physalis lives at the surface of the ocean. The gas-filled bladder, or pneumatophore, remains at the surface, while the rest of the organism is submerged. Since the man o' war has no means of propulsion, it is moved by a combination of winds, currents, and tides. Although it can be found anywhere in the open ocean (especially warm water seas), it is most commonly found in the tropical and subtropical regions of the Pacific and Indian oceans and in the northern Atlantic Gulf Stream.
A small fish, Nomeus gronovii (the man of war fish or shepherd fish), is partially immune to the the poison fromthe man of war's and can live among the tentacles but does avoid the larger, stinging tentacles, but still feeds on the smaller tentacles beneath the gas bladder. The Portuguese man of war is often found with a variety of other marine fish, including clownfish and yellow jack. The clownfish can swim among the tentacles with impunity.
A small fish, Nomeus gronovii (the man of war fish or shepherd fish), is partially immune to the the poison fromthe man of war's and can live among the tentacles but does avoid the larger, stinging tentacles, but still feeds on the smaller tentacles beneath the gas bladder. The Portuguese man of war is often found with a variety of other marine fish, including clownfish and yellow jack. The clownfish can swim among the tentacles with impunity.
Aequorea victoria
The Aequorea victoria or the Crystal Jelly is a bioluminescent hydrozoan jellyfish, or hydromedusa, that is found off the west coast of North America. Aequorea victoria typically feed on soft-bodied organisms, but the diet may also include some crustacean zooplankton and other plankton. Gelatinous organisms consumed include ctenophores, appendicularians and other hydromedusae, including rarely other Aequorea victoria if conditions are appropriate. Prey is ensnared in long tentacles containing nematocysts, and ingested with a highly contractile mouth that can expand to consume organisms half the medusae’s size. Due to their voracious nature, Aequorea victoria density can be inversely correlated to zooplankton density, indicating a competitive presence in shared environments. This jellyfish is capable of producing flashes of blue light by a quick release of calcium which interacts with the photoprotein aequorin. The blue light produced is in turn transduced to green by the now famous green fluorescent protein. NG