Diversity of Arthropods

1. Diversity of Arthropods

2. 4 Subphyla • Trilobita- Extinct Trilobites • Chelicerata- Spiders, Scorpions, and Ticks • Crustacea- Shrimp, lobster, crayfish, and barnacles • Uniramia- Insects, Centipedes, and Millipedes

4. Subphyla Trilobita • EXTINCT • Marine • Head and Segmented trunk with one pair of legs per segment • Single pair Antennae • Gills

5. Subphyla Chelicerata • 2 classes • Xiphosura- Horseshoe Crab • Arachnida- Spiders, Scorpions, Ticks and Mites

6. Chelicarata Characteristics • Two Segments • Cephalothorax • Abdomen • No Antenna • Simple Eyes called Ocelli • Six pairs of Jointed Appendages • Chelicerae- Claws or Fangs (1 pair) • Pedipalps- Feeding, Walking, Sensing (1pair) • Walking Legs- Movement (4 pair)

7. Chelicerata Cont… • Phylum Arthropoda • Subphyla Chelicerata • Class Xiphosura • Class Arachnida • Order Aranaea • Order Scorpionida • Order Acari

8. Horseshoe Crabs • Class Xiphosura • NOT TRUE CRABS • Marine • Book Gills for breathing

9. Class Arachnida • Terrestrial • 8 Legs • Chelicerae or Fangs with Venom • Ocelli • No Antenna • Breathe through Book Lungs • (Some species may have tracheal tubes)

10. SpidersOrder Aranaea • 8 simple eyes (ocelli)- Detect light, do not form images • 6 pairs of appendages • 1st pair: Chelicerae, modified pincers to hold/handle food or fangs to inject venom • 2nd pair: Pedipalps- handle/sense food, some males use to deliver sperm during reproduction • 3rd-6th pair: legs used for locomotion, located on cephalothorax

11. Spiders Cont… • Fangs pierce prey, inject poison, & suck out body fluids (feed primarily on insects, a few species feed on small vertebrates) • Have silk glands to make silk & spinnerets to release silk for webs • Lay eggs in silken sacs, young resemble adults and are often cannibalistic • Most spiders are solitary except at mating

12. Ticks and MitesOrder Acari • Most abundant Arachnid • Only 1 body section-Head, thorax, and abdomen are completely fused • Ticks are external parasites • Can be found on reptiles, birds and mammals • Mites are small and often invisible to naked eye • Parasitic while some adults can be free-living

13. ScorpionsOrder Scorpionida • Multiple body segments • Cephalothorax and long segmented abdomen • Pedipalps modified into Enlarged Pincers • Up-Curved tail ends with a poisonous stinger • Common in southern and southwestern United States • Nocturnal, feed mostly on insects and spiders • Breathe through Book Lungs • Give birth to live young

14. Subphyla Uniramia • 3 Classes • Chilopoda- centipedes • Diplopoda- millipedes • Insecta- insects

15. CentipedesClass Chilopoda • ·Are carnivores, also eat soil arthropods, snails, worms, and slugs • ·They bite • ·Have 1 pair of legs per segment; have 15 to 181 segments (always odd numbers); 1st segment has a pair of poison claws • ·  Have tracheal tubes w/ 1 pair of spiracles on each segment • · Most lay eggs

16. MillipedesClass Diplopoda • · Eat plants and dead materials • · Have 2 legs per segment; can have 100+ segments; • · Have tracheal tubes; each segment has 2 spiracles • · do not bite • · spray obnoxious smelling fluid as defense mechanism • · lay eggs in a nest and guard them

17. InsectsClass Insecta • Entomology – study of insects • Largest group of arthropods • Generally have 3 pair legs, usually 2 pair of wings, 1 pair antennae and 3 body regions • Mate once or only a few times • Internal fertilization, shell forms around them, then female lays eggs (large number increases chance of survival)

18. Metamorphosis • Most go through a metamorphosis – series of changes, controlled by hormones. • Usual 4 stages of development 1.egg 2.larva - free-living, wormlike stage 3.pupa – period of reorganization; larva organs and tissues breakdown and are replaced w/adult tissues 4.adult • Complete metamorphosis is an advantage because young do not compete w/adults for food. Example – caterpillar to butterfly

19. Caterpillar > Butterfly • In pupal stage, larval tissues break down & cells called imaginal disk develops into tissues of the adult • Cocoon or chrysalis is a protective case formed around the pupa • Metamorphosis controlled by hormones • Different stages have different functions (caterpillar/growth & adult/reproduction)

21. Insects Cont… • Many other insects go through 3 stages – gradual or incomplete metamorphosis • 1. egg 2.nymph – looks like adult but smaller, lacks certain appendages and cannot reproduce. 3.adult Example – grasshoppers or cockroaches • Respiratory system is a tracheal system with spiracles • Have both compound and simple eyes, most adults have just 2 compound eyes that may cover much of the head

22. Success of Insects • Found everywhere except in deep part of ocean • Very short life span & rapidly adapt to new environments • Small size helps minimize competition in habitats • Flight helps escape predators & move into other environments

23. Defense Mechanisms • Wasps & bees can sting • Some insects use camouflage to blend into their environments • Some insects taste bad & have warning colorations • Some insects spray noxious chemicals.

24. Environmental Impact • Pollinate almost 2/3's of all plants • Serve as food for fish, birds, & mammals • Help recycle materials (termites recycle wood) • Make useful byproducts such as silk & honey • Some spread disease • Agricultural pests

25. Crabs, Lobsters, Crayfish, & ShrimpSubphyla Crustacea • Most are aquatic, w/gills • Have mandibles for crushing food; move side to side instead of up and down • 5 pair walking legs used for walking, for seizing prey, and for cleaning other appendages • 1 pair antennae and 1 pair antennules • 2 compound eyes which are usually on movable stalks • Swimmerets, located on abdomen, create water currents, which enhance aeration of gills; some females use them to hold eggs until hatching, males use it as a copulatory structure