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  • 1. Chapter 9Phylum Arthropods “joined appendages”
  • 2. Abundant!• >83% of animals found have been arthropods• The great survivors – Over 500 million species
  • 3. Incredibly adapted• Successful: – Been around for over 500 million years – Large numbers – Live in extreme conditions – Ecological niches• Gammarus wilkitzkii• Scolopendra gigantea
  • 4. Characteristics of all Arthropods• Hard exterior (exoskeleton)• Joined appendages• Highly evolved nervous systems• Segmented body• 2 main groups – Chelicerates and mandibulates
  • 5. THE EXOSKELETON• Provides – Structural support – Protection – Prevention of water loss – System for muscle attachment and movement• Gas exchange• Soft tissue for joints• Molting: shedding of exoskeleton to allow growth
  • 6. Adaptive features• Tagmatization – Specialized segments of body • Feeding • Locomotion • Digestion • Sensory perception etc.• Metamorphosis – Radical change in body – Reduces competition between adults and larva
  • 7. Chelicerates• Primitive Arthropods• Characteristics – 6 pairs of appendages • 1 oral appendage (chelicerae) used for feeding – Lack actual mouth parts for chewing so “suck up predigested food” – Cephalothorax-largest – Abdomen –contains gills
  • 8. • Representative species – Horseshoe crabs and sea spiders• Reproduction – Sexual: separate sexes • Sea spiders: males carry fertilized eggs ( only marine invert to do this!!!!!) • Horseshoe crabs: external fertilization; females lay eggs in sand and when hatch carried to sea by high tide• Digestion – Horseshoe crab: scavengers; will eat anything – Sea spiders: carnivores; feed on cnidarian juice!!
  • 9. Mandibulates (Crustaceans)• Characteristics – Mandible: pair of appendages at anterior end used for feeding – 3 main body regions: head, thorax and abdomen – 2 pairs of antennae – Remaining appendages used for locomotion – Molting: as animals grows, new exoskeleton is formed and old one is shed • The shell does not grow with the crustacean
  • 10. Crustaceans• Reproduction • Digestion – Separate sexes/internal – Variety of feeding fertilization habits(depend on species) • Males special • Majority are predatory appendage modified scavengers for holding onto – Large inverts are prey for female and most depositing sperm. » Ex Alaskan king crab • Eggs are incubated by feed on bivalves » Hermit Crabs and female; larvae stage shrimp-scavengers when hatched feed on detritus » Fiddler crabs-deposit filter feeders
  • 11. Crustaceans – Reproduction • Sexual – Separate sexes – Some species internal fertilization/ others spawners – Life cycle 6 months to 6 years• Copepods – Most abundant of zooplankton – Suspension feeders – Carnivorous – Sexual reproduction
  • 12. Class Cirripedia “barnacles”• Characteristics – Only sessile crustaceans – Shell of calcium carbonate• Digestion• Filter feeders: use appendage “cirriped”• Reproduction – Hermaphrodites: cross fertilize – Larvae move until finds a substrate and metamorphoses into adult-> remain sessile
  • 13. The Food Chain• Ecological Role – Main diet of certain marine mammals • Keystone species of Antarctic food web • Blue whales eat 40 million krill a day – So why havent krill gone extinct? – Krill
  • 14. Ecological Roles of Arthropods• Essential links in food chains• Nutrient recycling• Food sources for humans and many other animals• Symbiotic relationships – Some can remove parasites – cleaner shrimp• Some have become invasive when introduced
  • 15. Do they look familiar?
  • 16. Phylum Arthropoda: SubphylumCrustacea Trilobita Chelicerata Atelocerata
  • 17. Subphylums• Trilobita • Crustacea – Extinct – Lobsters – Shrimp• Chelicerata – Crabs – Horseshoe crab – Water fleas – Sea spiders – Copepods – Spiders – Barnacles – Sowbugs – Scorpions • Atelocerata – Harvestmen – Millipedes – Mites and ticks – Centipedes – Hexapods