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SECTION CRUSTACEANS .. 24.2 Reinforcement KEY CONCEPT Crustaceans are a diverse group of ancient arthropods. A crustacean is an aquatic arthropod with a segmented body, a hard exoskeleton, two pairs of antennae, and one pair of appendages per segment. Crustacean bodies are made of two distinct body sections:. . The cephalothorax is the region of an organism that combines the head and trunk region into one long section: Part of this section is covered by a carapace which . serves to protect vital organs such as the gills." . The abdomen is the rear portion of the organism. .. There is a wide variety of crustaceans on Earth and many are vital'to ecosystem. function. Some crustaceans are predators of small fish, mollusks, and worms. Many crustaceans such as shrimp, lobsters, and crabs are a main food source for birds, fish, seals, and even humans. Crustacean appendages take a variety of forms, but millions of years ago they probably all looked the same. Natural selection has modified these appendages to serve functions A Closer that vary from sensing the environment, defending against predators; walking, feeding, and even attracting mates. Probably the best known crustacean appendages are the large olaws of lobsters and crabs. These claws are called chelipeds and are used for collecting and manipulating food. All crustaceans have two pairs of antennae on their . head. These appendages are used for sensing the surrounding environment to locate food and mates and to avoid predators. Crustacean mouths have highly adapted appendages called mandibles. Mandibles are . used to crush and bite food before sweeping it into the animal's mouth. Many crustacean legs are actually appendages adapted for swimming and walking. . The most commonly known crustaceans are the decapods, which include lobsters, crabs, and shrimp. But there are other types of crustaceans. Barnacles are the non-moving filter feeders that can be seen attached to the bottom of boats, while isopods are the. group of terrestrial crustaceans known as pill bugs and wood lice. Tongue worms are. parasites that live in the lungs and nasal passages of vertebrate-hosts. 1. What are the characteristic features of crustaceans? Aquatic arthropod with a segmented body , a hard exoskelton, two pairs OF Antennae, and one, pair Of 2. Name four important crustacean appendages and what they are used for. appendages .pe 3. What are four types of crustaceans? Unit 8 Resource Book 2 Reinforcement McDougal Littell Biolog