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Arthropods • Malpighian Tubules: Sac-Like Organ That Extracts Wastes from the Blood and Adds Them to Feces That Move Through the Gut

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Arthropods • Malpighian Tubules: Sac-Like Organ That Extracts Wastes from the Blood and Adds Them to Feces That Move Through the Gut • Phylum Arthropoda • Insects, crabs, centipedes, spiders • Segmented body • Tough exoskeleton made of chitin • Jointed appendages • Fewer body segments • Highly specialized appendages for feeding, movement and other functions • Complex organ systems; some only found only in this phylum • Tracheal tubes (respiration) • Open circulatory system • Excrete wastes through saclike tubules • Herbivores, carnivores, omnivores, bloodsuckers, filter feeders, detritivores, and parasites • Mouthparts have evolved to allow them to eat anything imaginable • Pincers or fangs to sickle- shaped jaws that can cut through the tissues of captured prey • Tracheal tube: one of many branching, air-filled tubes that extend throughout the body • Spiracle: small opening located along the side of the body through which air enters and leaves the body • Book lung: organ that has layers of respiratory tissue stacked like the pages of a book: used to exchange gases • Respire through feather-like gills (i.e. lobster and crabs) • The horseshoe crab respires through organs: book gills • Open circulatory system • Well-developed heart pumps blood through arteries that branch and enter the tissues • Blood leaves the blood vessels and moves through sinuses, or cavities • The blood recollects in a large sinus surrounding the heart • It reenters the heart and is again pumped throughout the body Terrestrial Arthropods • Malpighian tubules: sac-like organ that extracts wastes from the blood and adds them to feces that move through the gut Aquatic Arthropods • Diffusion moves cellular wastes from the arthropod’s body into the surrounding water • Well-developed nervous system • Brain • Sophisticated sense organs, (i.e. eyes and taste receptors) • Well-developed groups of muscles that are coordinated and controlled by the nervous system • Allows arthropods to beat their wings against the air to fly, push their legs against the ground to walk, or beat their flippers against the water to swim Terrestrial Arthropods • Internal fertilization • Sperm or sperm packet Aquatic Arthropods • Internal or external fertilization Molting • As the time for molting approaches, skin glands digest the inner part of the exoskeleton and other glands secrete a new skeleton • The animal pulls itself out of the remains of the original skeleton…this can take several hours • The new exoskeleton is soft and the animal is vulnerable to predators • Classified based on the number and structure of their body segments and appendages-particularly their mouthparts • Crustaceans • Spiders and their relatives • Insects and their relatives Crustaceans Primarily aquatic Common characteristics: 2 pairs of branched antennae 2 or 3 body sections Chewing mouthparts called mandibles Examples: Crabs Lobsters Crayfish Shrimp Barnacles • 2 pairs of branched antennae • 2-3 body sections • Mandibles: chewing mouthparts • Primarily aquatic • Examples: Crabs, shrimps, lobsters, crayfishes, and barnacles • Range in size from small terrestrial pill bugs to spider crabs that have masses around 20 kg • Cephalothorax: region of a crustacean formed by the fusion of the head with the thorax • Thorax: body part of crustacean that lies just behind the head and houses most of the internal organs • Abdomen: posterior part of an arthropod’s body • Carapace: the part of the exoskeleton that covers the cephalothorax • Mandible: mouthpart adapted for biting and grinding food • Cheliped: one of the first pair of legs of decapods (five pairs of legs: crayfishes, lobsters and crabs) • Swimmerets: flipper-like appendages used by decapods for swimming Spiders & Relatives Common characteristics: Chelicerae – pair of fangs used to stab & paralyze prey with venom Pedipalps – appendages near mouth used to grab prey 2 body sections 4 pairs of walking legs 2 main groups: Horseshoe crabs Oldest living arthropods (little change in 500 million years) Arachnids: Spiders Mites Ticks Scorpions • Chelicerates • Mouthparts: chelicerae • 2 body sections • 4 pairs of walking legs • Horseshoe crabs, spiders, ticks, and scorpions • The oldest living arthropods • First appeared more than 500 mya and have changed little since that time • Not true crabs at all! Anatomy is closer to that of spiders • Chelicerae, five pairs of walking legs, a long spike- like tail used for movement • The largest group of arachnids • Spin webs of a strong, flexible protein called silk • Do not have jaws for chewing: must liquefy food to swallow it • Chelicerae: pair of mouthparts in chelicerates that contain fangs and are used to stab and paralyze prey • Pedipalps: pair of mouthparts in chelicerates that are usually modified to grab prey • Spinneret: organ in spiders that contains silk glands • Small arachnids that are usually parasitic • Chelicerae and pedipalps are specialized for digging into a host’s tissues and sucking out blood or plant fluids • Mouthparts are so strong that if you try to pull off a tick the cephalothorax may separate from the abdomen and remain in your skin • Widespread in warm areas around the world • Have pedipalps that are enlarged into claws • The long, segmented abdomen of a scorpion carries a venomous stinger that can kill or paralyze prey • Chew their prey using their chelicerae Insects & Relatives Uniramia (i.e. insects, millipedes, & centipedes) Common characteristics: One pair of antennae Jaws Examples: Insects 3 body segments (head, thorax, abdomen) 3 pairs of legs (attached to thorax) Extremely variable body designs Centipedes May have few or many legs (more than 100) Carnivorous with a pair of venomous claws Millipedes May have up to 750 legs (typically 36 – 400) Usually feed on dead & decaying material May secrete toxic chemicals in defense • Uniramians have jaws, one pair of antennae, and unbranched appendages • A group that contains more species than any other group of animals living today • Wide variety of forms and lifestyles – Centipedes – Millipedes • Have a body divided into three parts: – Head – Thorax – Abdomen • Three pairs of legs are attached to the thorax • Like all arthropods, insects have a segmented body, exoskeleton, and jointed appendages • Multiple of sense organs are used to respond to stimuli • Compound eyes • Chemical receptors for taste and smell on their mouthparts • Well-developed ears that hear sounds far above the human range • Three pairs of appendages that are used as mouthparts, including a pair of mandibles • Adaptations for feeding are not restricted to their mouthparts • Many produce saliva containing digestive enzymes that help break down food • 3 pairs of legs • Used for walking, jumping, flying, capturing and holding prey, etc. • The evolution of flight has allowed insects to disperse long distances and to colonize a wide variety of habitats • Incomplete metamorphosis: type of insect development characterized by a similar appearance throughout all stages of the life cycle • Nymph: immature form that lacks functional sex organs and other adult structures • Complete metamorphosis: type of insect development in which the larvae look and act nothing like their parents and also feed in completely different ways • Pupa: stage of metamorphosis in which an insect changes from a larva into an adult • Many insects are known for their negative effects • Termites destroy wood structures, moths eat their way through wool clothing, etc. • Despite their association with destruction and disease, insects contribute to agriculture by pollinating 1/3 of the food that you eat • Produce commercially valuable silk, wax and honey • Communicate using sound, visual, chemical, and other types of signals • Much of the communication involves finding a mate • Pheromones: specific chemical messengers that affect the behavior of development of other individuals of the same species • Ants, bees, termites, and some of their relatives form complex associations called societies • Society: a group of closely related animals of the same species that work together for the benefit of the whole group • Caste: group of individual insects specialized to perform particular tasks, or roles Australian termites have Arthropods Mayflies live been known to build mounds for over a year Coelomates, bilateral twenty feet high symmetry, cephalized as larvae, but only a few and at least 100 Chitinous exoskeleton hours as feet wide. Segmented bodies adults The larva of the Paired, jointed appendages polyphemus moth Highly specialized appendages consumes 86,000 The for feeding, movement, & other times its birth weight praying functions in its first 56 days mantis is the only 3 major Subphyla: Spider silk is the insect that Uniramia (i.e. insects, strongest fiber can turn millipedes, & centipedes) known to man. its head. Crustacea (i.e. shrimp, A bee must visit lobsters, crabs, & barnacles) 4,000 flowers in Chelicerata (i.e. spiders, ticks, order to make scorpions, & termites) one tablespoon Scorpions fluoresce of honey. green under Out of the 40,000+ species ultraviolet light. of spiders, only about 200 are dangerous to humans. .
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