Mollusca
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Phylum: Mollusca
The phylum mollusca incorporates all mollusks. There are almost 47,000 species in the phyla. Mollusks are known for their soft bodies surrounded by hard shells. A few species like Octopus' and squid have evolved to not need a hard shell to protect them anymore. all mollusks have a defining trait called a coelom. The coelom gives the animals organs a space and protection. Mollusca are also bilaterally symmetrical, which means they look the same on either side. They are well developed, and all have a defined head and foot, as well as many having gills for underwater respiration.
Octopus Digestive System
An octopus' digestive system comprises of a two opening system, with a mouth and anus. They mainly eat crabs, lobster, and other small sea creatures. To eat them, they first capture it with one of their many suckered tentacles. Next they have to get into the hard hell. To do this, they have developed three ways. They can use tentacles and brute force to pull the shell apart, use their beak to bite the shell apart, or drill through the shell with toxins that seperate and dissolve connective tissue. They then use their radula, a toothed tongue, to rip the flesh out of the prey. After the meat is accesed, it goes down the esophahus through the buccal mass, into the stomach where acids digest it. Waste from this proccess is sent through the intestine out through the anus.
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This video shows an octopus eating a crab
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Scallop Digestive System
A scallops digestive system is different then most because they are filter feeders. They get food by pumping water through their body with the cilia. while the water is in the shell, the cilia and the mucous on the gills catch food particles. These particles are moved to the mouth, where they then go through the esophagus into the stomach. Here extracellular digestion takes place. the food then moves into the intestine, passes through the heart, and intracellular digestion takes place. The waste is then moved to the anus where it is excreted.
Gastropods (Snails and Slugs)
Gastropods digestive system is similar to that of an octopus. It starts by going in through the jaw into the buccal cavity, where it is prepared for digestion. it then goes through the esophagus into the stomach, where it is digested and broken down. The waste then travels down the intestine to the rectum, and out the anus.