Inside a squid.Squid are invertebrates: animals without backbones. Most animals in the world--about 99 percent of all species--are invertebrates. What else makes a squid different from vertebrates like you? Check out the diagram below, then read about three other ocean invertebrates at far right. ESOPHAGUS esophagus (ĭsŏf`əgəs), portion of the digestive tube that conducts food from the mouth to the stomach. When food is swallowed it passes from the pharynx into the esophagus, initiating rhythmic contractions (peristalsis) of the This tube connects the mouth to the stomach. Since the esophagus passes directly through the brain, a bite of food that's too big can kill a squid instantly! GLADIUS This feather-shaped blade runs beneath the mantle. Made of a material like that of human fingernails, the gladius is the squid's only body support. SUCKERS Squid suckers have the dangerous combination of a suction cup suction cup n. A cup-shaped device, usually of plastic or rubber, designed to adhere to a flat surface by means of suction. Noun 1. and a ring of sharp "teeth" to hold tight to predator or prey. INK SAC ink sac n. An ink-containing organ located near the rectum in most cephalopods, including the octopus, squid, and cuttlefish. When threatened, the squid squirts a mixture of dark ink and mucus from its ink sac out through its funnel. The cloud distracts the pursuer. Meanwhile, the squid jets away. GILLS Squid breathe using gills. Water flows into the mantle and around the gills, which absorb oxygen from the water and release carbon dioxide carbon dioxide, chemical compound, CO2, a colorless, odorless, tasteless gas that is about one and one-half times as dense as air under ordinary conditions of temperature and pressure. . RADULA rad·u·la n. pl. rad·u·lae A flexible tonguelike organ in certain mollusks, having rows of horny teeth on the surface. [Latin r Think of radula as a tongue with rows of backward-pointing hooks. The radula pushes food down the squid's esophagus. BEAK Make a fist. Now cup your other hand around the fist. That's the size of a giant squid's beak. The squid uses its beak to tear food into bite-sized chunks. MANTLE AND FUNNEL The mantle (the squid's body) and funnel work together to "jet propel" the squid through water: The squid takes in water through openings in the mantle. The mantle "locks" and squeezes, forcing water out through the funnel. This pushes the squid forward. The squid can point its funnel to move in any direction. TENTACLES Two long tentacles are used to help a squid snatch its prey-fish and other squid. ARMS A squid's eight arms help pass food to the beak. RELATED ARTICLE: No Bones About 'Em Crabs belong to another group of invertebrates called crustaceans, just like shrimp and lobsters. Instead of a gladius, crustaceans have an exoskeleton exoskeleton /exo·skel·e·ton/ (-skel´e-ton) a hard structure formed on the outside of the body, as a crustacean's shell; in vertebrates, applied to structures produced by the epidermis, as hair, nails, hoofs, teeth, etc. , a hard outer shell to support and protect their bodies. Sponges are the simplest type of invertebrate invertebrate (ĭn'vûr`təbrət, –brāt'), any animal lacking a backbone. The invertebrates include the tunicates and lancelets of phylum Chordata, as well as all animal phyla other than Chordata. . They don't have organs, they can't move, and most don't have a regular body shape. Sponges filter food and oxygen from water that flows into small holes in its body. Octopuses are close relatives of squid. They also have eight arms, suckers, and move by jet propulsion jet propulsion, propulsion of a body by a force developed in reaction to the ejection of a high-speed jet of gas. Jet Propulsion Engines The four basic parts of a jet engine are the compressor, turbine, combustion chamber, and propelling nozzles. . Octopuses and squid belong to a larger group of invertebrates called mollusks, a category that includes clams, snails, and slugs. |
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