Cnidarians are a phylum of aquatic organisms that include jellyfish, corals, hydroids, and

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Cnidarians are a phylum of aquatic organisms that include jellyfish, corals, hydroids, and anemones. They are an ancient group of animals that are thought to have emerged more that 500 million years ago. They are characterized by their radial symmetry, their diploblastic bodies, and specialized cells called cnidocytes. Cnidarians are represented as either polyps or medusae. Sea anemones and corals are consistently found as polyps, and jellyfish have a polyp stage early in their development. These polyps are mostly sessile, but some have the ability to relocate themselves if necessary. When jellyfish mature they are medusae with a fully formed bell. When in the medusae stage jellyfish are completely mobile. Both of these forms are radially…show more content…
Spirocysts do not have any piercing elements, and are used to attach to prey and non-prey. (Östman, 2000) They secrete an adhering hydroscopic substance that allows the tube to adhere to substrates without piercing them. (Östman, 2000) Spirocysts are very tightly wound within a thin walled spirocyst, in comparison to the thick walled nematocyst. Spirocysts are only found in Anthozoans, and are usually used in conjunction with nematocysts to hold prey and envenomate it. (Östman, 2000) The success of this depends on how well the tentacles can adhere to its prey. The “intrinsic adherence” of the cnidarian firing the cnidae is measure by the amount of force it takes to remove a target from the tentacle. (Thorington and Hessinger, 1998) the total adhesive force, as calculated by Thorington and Hassinger is equal to the adhesive force of the spirocyst mucus (St) and the product of the number of cnidae ( mastigophore nematocysts (nm), and spirocysts (ns) discharging onto the target and their intrinsic adherence, ( mastigophore nematocysts (im), and spirocysts (is). When combined Adhesive force = St + (nm)(im) + (ns) (is) They found that the product of the number of cnidae and the intrinsic adherence for spirocysts had no effect on overall adherence, so they shortened the equation to Adhesive force = St + (nm)(im)

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