|Copyright: randy lafferty (cherokeechief)
|Date Taken: 2005-03-15|
|Camera: sony dsc p-52|
|Photo Version: Original Version|
|Date Submitted: 2006-09-20 3:57|
|[Note Guidelines] Photographer's Note|
An anemone is basically the typical polyp: a small sac, attached to the bottom by an adhesive foot, with a column shaped body ending in an oral disc. The mouth is in the middle of the oral disc, surrounded by tentacles armed with many cnidocytes, which are unique cells that function as a defense and as a means to capture prey. Cnydocytes contain cnidae, capsule-like organelles capable of everting, giving phylum Cnidaria its name (Campbell and Reece 2002). The cnidae that sting are called nematocysts. Each nematocyst contains a small vesicle filled with toxins— actinoporins— an inner filament and an external sensory hair. When the hair is touched, it mechanically triggers the cell explosion, that fires a harpoon-like structure which attaches to organisms that trigger it, and injects a dose of poison in the flesh of the aggressor or prey. This gives the anemone its characteristic sticky feeling. Interestingly the clownfish is immune to an anemone's sting. The poison is actually a mix of toxins, including neurotoxins, which serve to paralyze and capture the prey, which is then moved by the tentacles to the mouth/anus for digestion inside the gastrovascular cavity. Actinoporins have been reported as highly toxic to fish and crustaceans, which may be the natural prey of sea anemones. In addition to their role in predation, it has been suggested that actinoporins could act, when released in water, as efficient repellents against potential predators.
Sized and cropped for upload.
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