The Subphylum Crustacea

The Subphylum Crustacea - important(yum yum Krill and a few...

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The Subphylum Crustacea The Subphylum Crustacea, shown in Figure 19, contains 30,000 mostly marine species. A few species live in freshwater. Lobsters, crabs, crayfish, shrimp, copepods, barnacles, and several other groups of organisms belong to this subphylum. All crustaceans possess two pairs of antennae, a pair of mandibles, a pair of compound eyes (usually on stalks), and two pair of maxillae on their heads, followed by a pair of appendages on each body segment. Crustaceanbodies usually have a head, thorax, and abdomen. Crustaceans utilize gills for gas exchange. .
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Most crustaceans are free-living, but some are sessile and a few are even parasitic . Some crustaceans filter tiny plankton or bacteria from the water, while others are active predators. A few crustaceans scavenge nutrients from detritus. Many species, including lobsters, crayfish, barnacles, and crabs are economically
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Unformatted text preview: important (yum, yum). Krill, and a few other species, form the base of extremely important marine food chains . Still others are crucial in recycling nutrients trapped in the bodies of dead organisms. The subphylum contains several taxonomic classes. We will focus on one, the class Malacostraca, which includes the shrimp, lobsters, etc. The Subphylum Uniramia This subphylum contains arthropods that have unbranched appendages. The uniramian body has two or three tagmata, and an abdomen that has many segments. Appendages in the head region include paired antennae and mandibles, and also two pairs of maxillae. Gas exchange is by means of tracheae and spiracles. This subphylum include millipedes, centipedes, and insects....
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