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Arthropods Characteristics Arthropods-Insects 1. Makes up ¾’s of all 2. 3. 4. 5. animals species Includes insects, spiders, scorpions, millipedes, centipedes, crabs, lobsters & crayfish Anthropod means “jointed foot/leg” Jointed appendages (legs, antenna, mouth parts) Segmented body with paired appendages on each segment Arthropods • Millipedes & Centipedes Arthropods-Spiders 6. External exoskeleton made of chitin (carbohydrate) & protein for protection & support 7. Exoskeleton has 3 layersouter waxy layer repels water, middle layer has calcium for extra strength & inner layer has flexible joints for movement 8. Deuterostomes 9. Coelomate 10. Ventral nervous system Arthropods-Crabs & Barnacles Arthropods-Scorpions 11. Open circulatory system 12. Specialized sensory receptors & high degree of cephalization 13. Have simple or compound eyes & segmented antenna Arthropods-Lobsters & Crayfish Arthropods Movement & growth Arthropods-Horseshoe crabs 1. Muscles occur in bundles & are attached to inside of exoskeleton on each side of joints Arthropod-Growth 2. Exoskeleton must be periodically molted (shed) for organism to grow 3. Molting called ecdysis 4. Molting hormone released & causes epidermal cells to secrete enzymes that digest & loosen inner exoskeleton 5. New exoskeleton secreted by epidermal cells flexible at first & must harden so arthropod not vulnerable to predators so often stay in hiding after molting 6. Arthropods go through numerous molts Arthropods Evolution & Taxonomy Arthropods o Four subphyla oTrilobita- extinct trilobites oCrustacea- shrimps, lobsters, crayfish & barnacles o Chelicerata- spiders, scorpions & ticks o Uniramia- centipedes, millipedes & insects Arthropods o Subphyla trilobita o Includes extinct trilobite o Marine o Have a head & segmented trunk with one pair of legs one each segment o Breathe through gills o Single pair of antenna Subphylum Chelicerata • Characteristics – 1.Includes 2 classes- Xiphosura (horseshoe crab) and Arachnida (spiders, ticks, scorpions & mites) – 2. Have a cephalothorax (fused head & thorax) and abdomen Subphylum Chelicerata • Characteristics 8. Ticks & Mites a. Parasitic arachnid b. Need blood meal to molt c. Ticks carry Lyme disease & Rocky Mountain Spotted Fever 9. Scorpions a. Prefer dry regions b. Breath through book lungs c. Nocturnal predators Subphylum Crustacea Characteristics 1.Marine members include shrimp, lobster, copepods, barnacles & crabs 2. Terrestrial crustaceans called isopods includes pillbugs & sowbugs 3. Freshwater members include crayfish & Daphnia (water fleas) 4. All have jaws or mandibles for chewing or tearing 5. have 10 pairs of jointed appendages 6. Breathe through gills 7. Barnacles a. Marine b. Sessile crustaceans that live in limestone case c. Filter plankton with 12 appendages called cirri 8. Isopods (pillbugs & sowbugs) a. Some live on land in dark places • 9. Crayfish Subphylum Crustacea a. Antennules located on head help balance, touch & taste b. Statocysts- balancing organs at the base of antennules c. Maxille- paired mouthparts that move side to side to tear food d. Maxillipeds- help hold food e. Swimmerets- under abdomen to swim, gas exchange, & protect eggs/ young f. Abdomen ends in flat segment called telson with flat uropods on each side g. Chitinous teeth in stomach grind food h. Open circulatory system with heart to pump blood to gills & body cells i. Gills attached to walking legs Subphylum Crustacea Copepods a. Largest group of crustaceans b. Make up most of the marine plankton c. Serve as food for many marine animals d. Found in freshwater, marine & moist terrestrial environments Subphylum Uniramia • Characterists – 1.Includes 3 classes- Chilopoda (centipedes), Diplopoda (millipedes) & Insecta – 2. Most are terrestrial – 3. Exoskeleton prevents desiccation (water loss) • Class Chilopoda – 1.Terrestrail centipedes – VS (not) – 2. Have 1 pair of legs per body segment • Class Diplopoda – 1.Terrestrial millipedes – 2. Roll into balls when threatened & spray noxious chemical containing cyanide Stop! The head and thorax are covered by a common “shell,” or covering termed the “carapace.” The front end of the carapace has “the rostrum,” a spike-like projection from the front end. The eyes are on stalks and there are two sets of sensory appendages termed antennae. Each of the first pair of antennae has two branches. Each of the second pair of antennae has one long branch and a smaller scale-like branch at the base. The primitive forms have eight thoracic segments. Each thoracic segment bears an appendage that may be used for walking. Each thoracic appendage may bear a gill found up under and protected by the carapace. The abdomen projects beyond the carapace and has six segments. The first five abdominal segments have flap-like swimming appendages found underneath it. The last abdominal segment bears a pair of lateral flaps and is typically flattened. Together with the lateral flaps, it is often called the tail fan. • Crabs are flattened from top to bottom. • The first pair of remaining thoracic appendages ends in large pinching claws. • The last four pairs of thoracic appendages are walking legs. • The first abdominal segment is small. • The abdominal appendages are small and modified, and not used for swimming. • The abdomen is curved under the thorax where it fits in a groove on the animal's underside. True Crabs Arthropods of the PNW Barnacles Barnacles • Acorn barnacle • White acorn barnacle • Leaf barnacle True Crabs • Dungeness crab • (Shield-backed) Kelp crab • Purple shore crab True Crabs • Red crab • Oregon cancer crab Other “Crabs” • Hairy hermit crab • Pacific mole crab Shrimp • Broken (Stiletto)back shrimp Isopods & Amphipods • Vosnesensky’s isopod • Sand flea Sea Spiders • Stearns’ sea spider Sea Spiders Sea Spiders Sea Spiders Phylum Arthropoda • Class: Merostomata--horeshoe crabs • Class: Pycnogonida--sea spiders • Class Crustacea: (1)Subclass: Branchiopoda--fairy shrimp, brine shrimp (2) Subclass: Copepoda—copepods (3) Subclass: Cirripedia—barnacles (4) Subclass: Malacostaca: • Order: Stomatopoda--mantis shrimp • Order: Euphausiacea—krill • Order: Decapoda--shrimps, lobsters, crabs Stop