Chapter 26 Arthropods Joint limbed arthropods (1 min)

1. Chapter 26 ArthropodsJoint limbed arthropods (1 min)

4. Arthropod Characteristics • Segmented • Coelomates • Invertebrate • Bilateral symmetry • Exoskeleton (chitin) • Jointed appendages – which allow for more flexibility

5. Arthropod Senses • Antennae - detects movement, sound, and chemicals • Pheromones – communication chemicals • May have 2 compound eyes and 3 to 8 simple eyes • Simple eyes w/ one lens used to detect light • Compound eyes w/ many lenses used to detect movement and color

6. Arthropod Body Systems • Well developed nervous system • Open circulatory systems w/ one or more hearts • Complete digestive system w/ mouth, stomach, intestine, and anus

7. Other Systems • Malpighian tubules remove waste • Good muscular system attached to the inside of the exoskeleton • Most reproduce sexually • Internal fertilization (on land) • External fertilization (in water)

8. Parthenogenesis • Parthenogenesis - when an adult forms from an unfertilized egg (asexual reproduction) • In social insects (honeybees & ants) • unfertilized eggs (haploid) develop into the male drones • fertilized eggs (diploid) develop into the female workers and queens. • Used to increase reproduction rates.

9. Arthropod Molting • Exoskeletons are heavy and cannot grow • Arthropods molt (shed their exoskeleton) in order to grow. • Most molt 4 – 7 times • They are very vulnerable during this time

10. Arthropod Segmentation • Most have three body sections: • The head, thorax, and abdomen • Some have two body sections: • an abdomen and a cephalothorax (fused head and thorax)

11. Gas Exchange • Three types of respiratory structures: • Gills – found in aquatic species • Tracheal tubes – found in insects • Hollow air passageways • Spiracles are openings that allows air to enter or leave • Book lungs – found in spiders • Air-filled chambers with leaflike plates • Some diffuse air directly through the body

12. Diversity of Arthropods • Six classes of arthropods. • Arachnida, Crustacea, Chilopoda, Diplopoda, Merostomata, and Insecta • Amazing Arthropods (13 min)

13. Class: Arachnida • Examples: Spiders, scorpions, mites, & ticks • North America has only two species of spiders dangerous to people • Arachnids are found throughout the world in nearly every habitat, but they reach their greatest size and diversity in warm arid and tropical regions • 6 pairs of jointed appendages

14. Arachnid Characteristics • The body is divided into two parts • The anterior part, the cephalothorax • Has sense organs, mouthparts, and limbs in pairs • They do not have antenna • The first pair of limbs, the chelicerae, may form pincers or poison fangs • the second pair, the pedipalps, may serve as pincers, feelers, legs, hold reproductive parts • The other limb pairs, generally four, are used for walking. • The posterior part of the body, the abdomen • Has the genital opening • Has book lungs • Solitary except at the time of mating, when a variety of complex behavior patterns may be observed. Females may guard eggs or young, which are often born live.

17. Arachnida • Spiders use extracellular digestion • All spiders spin silk, but not all make webs • Spinnerets are used to spin silk • Ticks and mites have a single fused body section • Scorpions have many abdominal segments, large pincers, and a venomous stinger on their tail

18. Spider Silk • Spider's silk is made up of chains of amino acids (protein). • Spider silk is extremely strong -- it is about five times stronger than steel and twice as strong as Kevlar of the same weight. • Spider silk also has the ability to stretch about 30-percent longer than its original length without breaking, which makes it very resilient.

19. Spider Silk • Goats are being genetically altered to produce ‘spider silk’ in their milk. • A thread of silk the diameter of a pencil could lift a 747 • After a few days the web dries out and is no longer sticky. The spider eats and recycles the old web.

20. Normal 5x 20x

21. Spinnerets

23. Shown here is a close-up view of the pedipalps of a mature male Grammastola rosea (Chilean rose hair tarantula).

24. Flower spider

25. Black Widow Spider (26 min)

26. Crustaceans • Most crustaceans are aquatic and have gills • 2 pairs antennae • All have 2 compound eyes, usually on moveable stalks • Mandibles open sideways • Some have 5 pairs of walking legs • Pill bugs are the only land crustaceans

27. Examples of Crustaceans • Crabs Crustacean Video (3 min) • Lobsters • Shrimp • Crayfish • Barnacles Barnacles (18 sec) • Water fleas (Daphnia) • Pillbugs

30. Centipedes and Millipedes • Centipedes - class Chilopoda • Millipedes - class Diplopoda

31. Centipedes • Centipedes are carnivorous and have a painful bite using fangs • Centipedes have an odd number (15-181) of body segments • One pair of legs per segment • Generally flattened • Have a pair of well developed antennae on the head

32. Millipedes • Millipedes eat mostly plants • They don’t bite, but they can release a foul smelling fluid • Millipedes can have 100+ segments, each with 4 legs and two spiracles • Millipedes have more rounded bodies

33. South American Centipede Video (1 min)

35. Class: Merostomata • Horseshoe crabs are almost the same now as they were 500 million years ago during the Cambrian period and are called living fossils • They have a very effective exoskeleton

36. Horseshoe Crabs • The horseshoe crab has survived because it can go a year without eating and endure extreme temperatures and salinity • A horseshoe crab's tail, while menacing, is not a weapon. Instead, the tail is used to plow the crab through the sand and muck, to act as a rudder, and to right the crab when it accidentally tips over.

37. Horseshoe Crab Video (11 min)

38. Class Insecta • The largest class of arthropods! • Insects usually mate only once or they might mate only a few times during their lifetime • They lay many eggs at once • Eggs are fertilized internally • Insecta is the most successful and diverse class of organisms on earth

39. Class Insecta • Have 3 body segments • Have 3 pairs of legs • Have 1 pair of antenna • Many fly • Amazing World of Insects (26 min)

44. Metamorphosis • Many insects undergo metamorphosis from egg to adult • Complete Metamorphosis – egg, larva, pupa, and adult • Larva is wormlike and are called caterpillars • The pupa stage is a major change in body systems • Examples include butterflies, ants, wasps, beetles, etc.

46. Metamorphosis • Incomplete Metamorphosis – is a gradual change with three stages • Egg, nymph, and adult • Nymphs look like tiny adults • Examples are cockroaches and grasshoppers

48. Insect Metamorphosis (21 min)

50. Insect Fact and Folklore (22 min)