The Arthropods

1. The Arthropods Chapter 33

2. General statistics • Most numerous and successful phyla • 400,000 known plant species • 250,000 known non-arthropod animals • Over 1,000,000 species of arthropods.

3. 5 classes of arthropods diplopoda crustacea chilopoda Insecta arachnida

4. General characteristics • Arthropoda: • From the Greek word arthron meaning “joint” and poda meaning “foot” • 1) Jointed appendages used for crawling, swimming, flying, etc.

5. More characteristics 2. Possess an exoskeleton • Made up of protein and chitin • Helps to waterproof and prevent water loss • Main disadvantage: exoskeleton does not “grow” with the organism. Must be shed. • molting

6. 3. Segmented body • 4. Well developed nervous systems • 5. Open circulatory system

7. Class Crustacea • Lobsters, crayfish, crabs, shrimp. • Mostly marine, some fresh water. • All have 2 pairs of antennae on the head and 2 body regions.

8. The crayfish • Cephalothorax: fusion of the head and thorax • Antennules: first pair of appendages attached to the head. Shorter of the two pairs of antennae • Used for touch, taste, and balance

9. More appendages • 2nd pair : antennae (long) used for touch and tasting • Mandibles (jaws) 1 pair. Used for crushing food • Maxillae: 2 pairs. Used to handle food • Maxillipeds: 3 pairs. Touch, taste, handling of food

10. Chelipeds • Large first legs where claws are found. • Used for defense and grasping prey.

11. and more appendages • Walking legs (4 pairs) • Swimmerets : appendages found on the underside of the abdomen. • Used for swimming and carrying eggs and young.

12. Internal Structure • NUTRITION • Food is caught with the chelipeds, crushed by the mandibles and passed into esophagus. • Food then digested and wastes passed out the anus.

13. Excretion • Wastes from the blood are removed by the green glands in the head.

14. Circulation and respiration • Possess a dorsal heart. • Open circulatory system (no capillaries nor veins) • Arteries dump blood into open spaces, sternal sinus collects old blood and channels it to gills to pick up oxygen.

15. Hemocyanin = copper containing pigment in the blood that aids in transport of oxygen. • Gasses are exchanged at gills:

16. Nervous system • Well developed sensory organs • Compound eyes, many sensory hairs • Statocysts: sacs at the base of the antennules that aids in balance.

17. Reproduction • Separate sexes. Can determine sex by looking at first pair of swimmerets. • Male will have enlarged first pair of swimmerets to transfer sperm to seminal receptacle of female during the fall. • Eggs attach to swimmerets and hatch in the spring. • Young stay attached until self sufficient.

18. Baby crayfish:

19. Class Chilopoda (centipedes) • “centipede” literally means 100 feet • Usually 30 to 60 legs, can be as many as 350 legs • A distinct 6 segmented head • Worm-like body with similar segments.

20. More centipede facts • All body segments have one pair of legs except the one behind the head and the last two. Fairly fast crawlers • Feed on insects using poison claws. • Usually found in dark damp places • Under logs and rocks, in basements

21. Class diplopoda (millipedes) • Literally 1000 legs although no species has this many legs. World record is 750 legs. • Usually anywhere from 100 to 300 legs. • Two pairs of legs per body segment except for the last two segments. Slow moving • No poison claws; feed on decaying plant material.

22. Class arachnida • Spiders, scorpions, ticks, and mites • Mostly free-living. A few parasitic • Some are harmful to humans (poisonous cause disease) • Mostly helpful • Get rid of pests like mosquitos

23. Ticks • Can cause disease ex. • Spotted Rocky Mt. Fever • Lyme Disease

24. Lyme Disease • Carried by deer ticks. Caused by a bacterium. • Usually in wooded areas of Mid-Atlantic states and New England.

25. spiders • 2 body segments • Cephalothorax (6 pairs of appendages) • Adbdomen • No antennae or Chewing jaws

26. chelicerae • First pair of appendages • Also known as the “fangs” of a spider • Will inject a poison into its prey.

27. pedipalps • Found between the first pair of legs and the chelicerae. • Used for sensing chemicals and touch • Used to manipulate food.

28. Abdomen appendages: • 4 pairs of walking legs • Book lungs = respiratory organs on underside of abdomen • Spinnerets: posterior end of abdomen, used to make silk for webs and raising and lowering themselves.

29. Class insecta • Most successful class of arthropods: 30 orders • Live in all habitats • High reproductive rates (all reproduce sexually) • Small in size • Only invertebrates capable of flight

30. Why is flight such an advantage? • Escape form enemies • Search for food • Allow insects to inhabit environments not inhabited by other organisms. • Less competition for natural resources.

31. 3 body regions: • Head (mouthparts, antennae, eyes) • Thorax (3 pairs of legs, wings) • Abdomen (respiratory structures)

32. Specialized structures: • Mouthparts 2 main types: sucking chewing

33. legs • Used for swimming, collecting pollen. Defense, grasping prey, jumping

34. Incomplete metamorphosis • Series of changes where an insect grows from eggs to a nymph to an adult • Nymph = immature form that closely resembles the adult form except for certain features. • Examples: grasshoppers, crickets

35. Complete metamorphosis • 4 stages: • Eggs, larva, pupa, adult • Larval stage examples: caterpillars, maggots • Pupa: cocoon • Changes are controlled by hormones. • ex.

36. Grasshopper (order Orthroptera) • Head • 2 large compound eyes • 3 simple eyes • 1 pair of antennae • Mouthparts located outside the mouth(mandible, maxilla, special tongue-like organ)

37. Thorax • 3 separate segments to the thorax with each possessing a pair of legs • Each leg has five segments ending in a clawed tarsus or foot • 1st and 2nd pairs of legs are for crawling. • Last pair used for jumping • 2 pairs of wings

38. Abdomen • Made up of 10 segments • Each segment has one pair of spiracles (openings into air tubes) • 1 pair of tympanum (hearing organs) • reproductive organs

39. Female abdomen • Ovipositor = hard four pointed organ at the base of the abdomen used to dig holes for burying eggs.

40. Harmful effects of insects: • Cause millions of dollars in crop damage. • examples: • Corn smut, rootworm, locusts, tent caterpillars

41. Images:

42. Transmit diseases • Malaria = transmitted by mosquitoes • West Nile virus = also mosquitoes • West Nile link

43. Destroy property • Cockroachestermites moths

44. Economic value of insects: • Help pollinate fruit trees • Produce honey • Kill other harmful insects • Eat dead plant and animal material

45. Ways to kill insects: • Most common: insecticides • Trap and sterilize males • Genetic engineering • Bt corn

46. Phylum Echinodermata • Literally means “spiny-skinned” • All marine • Examples: starfish sea urchin

47. characteristics • Well developed coelom • Endoskeleton • Simplest organism showing embryological formation of the anus before formation of the mouth. • Radial symmetry

48. starfish • Usually five arms but can possess up to 20 arms • Extensive water-vascular system • Water will enter through the sieve plate and pass through a series of canals into each arm.

49. Tube feet • Small water filled tubes or projections on the ventral surface used for locomotion, respiration, grabbing prey, and digestion.

50. More starfish facts • Feed on clams and oysters • Skin gills = small finger-like appendages on the surface of starfish that is a site for respiration • Separate sexes • Can regenerate lost arms. An entire new starfish can grow as long as part of the central disk is present.