Chapter 36

1. Chapter 36 Arthropods

2. Objectives • Describe the distinguishing characteristics of arthropods. • Explain the process of molting in an arthropod. • List the five major subphyla of the phylum Arthropoda.

3. Characteristics of Arthropods • The members of the phylum Arthropoda are called arthropods. • Arthropods are segmented animals with body segments that bear appendages. Tarantula

4. Characteristics of Arthropods • Arthropods have an exoskeleton that provides protection and support and contains chitin. • Arthropods show a high degree of cephalization. Most have segmented antennae and compound eyes.

5. Characteristics of Arthropods • The rigid exoskeleton limits the size to which an arthropod can grow. • So, each arthropod periodically sheds its exoskeleton and makes a new one in the process of molting. • An anthropod goes through many cycles of molting during its life. Exoskeleton Link

6. Characteristics of Arthropods

7. Classification of Arthropods • Arthropods are usually divided into five subphyla on the basis of differences in development and in the structure of appendages, such as mouthparts. • The two major types of mouthparts are: • mandibles, which are jawlike • chelicerae (singular, chelicera), which are pincerlike

8. Chelicerae are the two iridescent green mouthparts. Mandibles of a Bull ant

9. Classification of Arthropods • The five main subphyla are: • Trilobita • Crustacea • Chelicerata • Myriapoda • Hexapoda

10. Crustacea Cooked Shrimp Cocktail Whole wild Pink Shrimp

11. Chelicerata Horse-shoe Crab

12. Myriapoda Centipede

13. Hexapoda Flesh Fly

14. Subphylum Crustacea • Describe the characteristics of crustaceans. • Compare aquatic crustaceans with terrestrial crustaceans. • Explain the functions of the appendages on a crayfish. • Summarize digestion, respiration, circulation, excretion, and neural control in crayfish.

15. Characteristics • The subphylum Crustacea contains about 38,000 known species. • Crustaceans are so diverse that their single defining characteristic is having two pairs of antennae. two pairs of antennae.

16. Characteristics • Most crustaceans also have: • a pair of mandibles • a pair of appendages on each body segment • some branched appendages • 16 to 20 segments and several tagmata Fiddler Crab Pinchers

17. Characteristics Some crustaceans respire through their exoskeleton, others respire through gills. • Many have a free-swimming larval stage called a nauplius.

18. Types • The crayfish is an abundant freshwater crustacean that is structurally similar to lobsters, which are marine crustaceans. • Crayfish, lobsters, crabs, and shrimp are decapods, or members of the order Decapoda. Decapoda means “10 feet.” • Decapods have five pairs of legs that are used for locomotion.

19. Crayfish External Structure External Structure • The crayfish’s body is divided into • the cephalothorax, which is covered by the carapace and is divided into • the head, which has five segments • the thorax, which has eight segments • the abdomen, which is is divided into six segments

21. Crayfish Internal Structures Digestion • Crayfish have a digestive gland that is near the stomach and that secretes enzymes for digestion. Respiration • Walking circulates water across the gills. Circulation • The circulatory system is open.

22. Crayfish Internal Structures Excretion • Green glands assist in excretion of excess water that enters the body by osmosis. Neural Control • The nervous system of the crayfish is typical of arthropods and is similar to that of annelids.

23. Crayfish Sensory Organs Sensory Organs • Crayfish sense vibrations and chemicals in the water with thousands of small sensory hairs. • Their compound eyes are set on two stalks.

24. Internal Anatomy of a Crayfish

25. Objectives Subphyla Chelicerata and Myriapoda • List the characteristics of arachnids, as represented by a spider. • Explain the adaptations that spiders have for a predatory life on land. • Identify the unique characteristics of scorpions, mites, and ticks. • Compare the characteristics of millipedes and centipedes.

26. Subphylum Chelicerata • The subphylum Chelicerata, the chelicerates, includes spiders, scorpions, mites, sea spiders, and horseshoe crabs. • Chelicerates lack antennae and typically have six pairs of appendages.

27. Subphylum Chelicerata • The first pair of appendages, the chelicerae, are modified into pincers or fangs. Chelicerate Green Pinchers

28. Class Arachnida • Class Arachnida, the arachnids, includes spiders, scorpions, mites, and ticks.

29. Class Arachnida • The arachnid’s body is divided into: • a cephalothorax that usually bears six pairs of jointed appendages: • one pair of chelicerae • one pair of pedipalps • four pairs of walking legs • an abdomen Deer Tick

30. Subphylum Chelicerata Anatomy of a Spider • Spiders have eight simple eyes and chelicerae that are modified as fangs. • Spiders produce silk threads using spinnerets.

31. Subphylum Chelicerata Anatomy of a Spider • Spiders respire through spiracles that connect to book lungs or tracheae. • Malpighian tubules function to excrete wastes while conserving water.

32. Anatomy of a Brown Recluse Spider

33. Spiders Feeding Habits • Spiders feed on insects and other small animals. Many species are adapted to capture certain prey. • Spiders rarely harm humans, but two species in the United States are dangerous: • the black widow • the brown recluse

34. Black Widow Brown Recluse

35. Life of a Spider • A male spider is usually smaller than the female. • Females lay eggs in a silken case.

36. Subphylum Chelicerata Scorpions Scorpions • Scorpions have large, pincherlike pedipalps and a stinger on the last segment of the abdomen.

37. Subphylum Myriapoda • Members of the subphylum Myriapoda have antennae, mandibles, and unbranched appendages. Class Diplopoda • Millipedes have rounded bodies and two pairs of jointed legs on each body segment except the last two segments.

38. Subphylum Myriapoda Class Chilopoda • Centipedes have flattened bodies and one pair of jointed legs on each body segment except the first segment and the last two segments.