The phylum mollusca is a large phylum of invertebrate animals. There are about 85,000 recognized species of mollusks.
Three types of mollusks are slugs, oysters,and squids.
SlugsThe primary organs in the excretory system of a slug are the nephridia. These organs produce either ammonia or uric acid as a waste product. The nephidrium has an important role in maintaining water balance in certain species. In some species, additional organs include pericardial glands in the body cavity and digestive glands opening into the stomach.
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OystersSimilar to the excretory system of a slug, the primary organs of an oysters excretory system are the nephridia. The nephridia consist of two long, glandular tubes which open up into the body cavity, just beneath the heart and bladder. Waste is voided from the bladders through a pair of openings near the front of the upper part of the mantle cavity from where it is washed away.
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SquidsIn squids, one of the excretory system's primary organs is the rectum. It is the rectum that passes out solid waste. Next to the rectum is the ink sac. The ink sac allows a squid to rapidly unload black ink into the mantle cavity.
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