Arthropods and Echinoderms

1. ArthropodsandEchinoderms

2. Phylum Arthropoda • Most diverse phylum • Most successful of all time • About 1 million species have been identified • = more than 3 times the number of all other animal species combined!!

3. What is an Arthropod • Includes insects, crabs, centipedes, and spiders • All have segmented bodies, tough exoskeletons, and jointed appendages

4. Exoskeletons • Provide protection and support • Made of protein and carbohydrate called chitin • Vary in shape, size and toughness • Terrestrial arthropods have waxy covering to prevent water loss

5. Appendages • Appendages: structures such as legs and antennae that extend from the body wall • All are jointed • Include antennae, claws, walking legs, wings, flippers, mouthparts, tails, and other specialized structures • Named for this: arthron means “joint” in Greek, and podos means “foot”

6. Evolution of Arthropods • First arthropods appeared in the sea more than 600 million yrs. Ago • Live in every habitat on Earth: sea, freshwater, land, and air • Evolution has led to fewer body segments and highly specialized appendages for feeding, movement, and other functions

7. Form and Function • Use complex organ systems • Feeding: herbivores, carnivores, and omnivores • Bloodsuckers, filter feeders, detritivores, and parasites • Mouthparts modified for chewing, sponging, sucking, and probing

8. Form and Function • Respiration • Terrestrial arthropods breathe through network of branching tracheal tubes that extend throughout the body • Air enters and leaves the tubes through spiracles: small openings located on outside of body • Spiders have book lungs: organs with layers of respiratory tissues stacked like a book • Aquatic arthropods use featherlike gills or book gills

9. Form and Function • Open circulatory system • Well-developed heart pumps blood through arteries that branch and enter the tissues • Leaves vessels moves through sinuses or cavities • Collects in large sinus surrounding heart • Re-enters heart and is again pumped through body

10. Form and Function • Excretion • Terrestrial arthropods use malpighian tubules: saclike organs that extract wastes from the blood and then add them to feces that move through the gut • Aquatic arthropods use diffusion to move cellular wastes from the body to the water

11. Form and Function • Well developed nervous systems • Have brains that receive information and send it out to muscles • Two nerves connect brain to a ventral nerve cord • Along nerve cord are several ganglia that coordinate movements of individual legs and wings • Sophisticated sense organs: compound eyes may have more than 2000 separate lenses to detect color and motion very well

12. Form and Function • Movement by well-developed groups of muscles made of individual muscle cells that contract and pull on exoskeleton • At each joint, different muscles either flex or extend

13. Form and Function • Reproduction • Terrestrial arthropods have internal fertilization • Some put sperm inside female, others deposit sperm packet that female picks up • Aquatic arthropods may have internal or external fertilization

14. Growth and Development • Exoskeleton does not grow, must be shed as arthropod gets bigger • Molting: shedding of entire exoskeleton and making a new one • Controlled by hormones • Can take several hours • Makes them vulnerable to predators while shell is still soft • Most hide during molting or molt at night

15. Groups of Arthropods • Arthropods are classified based on the number and structure of their body segments and appendages – particularly their mouthparts

16. Subphylum Crustacea • Mostly aquatic • Includes crabs, shrimps, lobsters, crayfishes, and barnacles • Range in size from small terrestrial pill bugs to enormous spider crabs up to 20 kilograms • Typically have 2 pairs of antennae, 2 or 3 body sections, and chewing mouthparts called mandibles

17. Subphylum Crustacea • Cephalothorax: anterior, fusion of head with the thorax • Thorax: holds internal organs • Abdomen: posterior part of the body • Carapace: part of the exoskeleton covering the cephalothorax

18. Subphylum Crustacea • 1st 2 pairs of appendages are antennae covered in sensory hairs • Used as sensory organs, filter-feeding, or swimming • 3rd pair are the mandibles adapted for biting and grinding food • Gills are attached to appendages associated with the cephalothorax

19. Subphylum Crustacea • Decapods: crayfish, lobsters, and crabs • Largest group of crustaceans • Five pairs of legs • 1st pair of legs called chelipeds, bear large claws modified to catch, pick up, crush and cut food • 4 pairs of walking legs • Along abdomen are several pairs of swimmerets: flipperlike appendages used for swimming • Final abdominal segment is fused to form a large, flat tail: uropod

21. Subphylum Chelicerata • Includes horseshoe crabs, spiders, ticks, and scorpions • Have mouthparts called chelicerae and two body segments and 4 pairs of walking legs • No antennae • Cephalothorax contains brain, eyes, mouth, and walking legs • Abdomen contains internal organs

22. Subphylum Chelicerata • Chelicerae contain fangs used to stab and paralyze prey • Pedipalps used to grab prey • Respire with either book gills or book lungs • Two main classes: Merostomata and Arachnida

23. Subphylum Chelicerata • Class Merostomata • Includes horseshoe crabs • Oldest living arthropods: first appeared 500 mya • Not true crabs at all • Anatomy similar to spiders • Have chelicerae, five pairs of walking legs, and long spikelike tail • Can grow to size to frying pan • Common along eastern US coast

24. Subphylum Chelicerata • Spiders: largest group of arachnids • Capture food in a variety of ways: webs made of protein called silk, stalk and pounce on prey (turantula), lie in wait then grab • Feed on animals ranging from other arthropods to small birds • No jaws for chewing, must liquefy food to swallow it

25. Subphylum Chelicerata • Once prey is caught, fangs inject paralyzing venom • Once prey is dead, spider injects digestive enzymes into the wounds • Spider sucks out tissues into a specialized pumping stomach • Food then moves to the rest of the digestive tract being further broken down by enzymes

26. Subphylum Chelicerata • All spiders produce silk even if they don’t spin webs • Stronger than steel! • Used for webs, cocoons for eggs, wrappings for prey • Force liquid silk through spinnerets: organs that contain silk glands • As silk comes out it hardens into single strand • Spinning webs seems to be preprogrammed behavior

27. Subphylum Chelicerata • Mites and Ticks: small and often parasitic • Specialized chelicerae for piercing tissue and sucking out blood • Pedipalps are often equipped with claws for holding on to host • Parasitize plants and animals • Can cause itching, painful rashes, and transmit diseases such as Rocky Mtn. spotted fever and Lyme disease

28. Subphylum Chelicerata • Scorpions: widespread in warm areas including southern US • Pedipalps enlarged into claws • Long, segmented abdomen has a venomous stinger that can kill or paralyze prey • Chew up prey with chelicerae

29. Subphylum Uniramia • Includes centipedes, millipedes, and insects • Response to stimuli • Compound eyes • Chemical receptors for taste and smell on mouthparts, antennae and legs • Sensory hairs to detect movement • Well-developed ears that hear above human range; found in strange places (behind legs in grasshoppers)

30. Subphylum Uniramia • Adaptations for feeding • 3 pairs of appendages for mouthparts including mandibles • Saliva contains digestive enzymes • Bee saliva help change nectar into honey • Glands in bee’s abdomen secrete wax, used to build beehives

31. Subphylum Uniramia • Movement and Flight • Legs used for jumping, walking, capturing and holding prey • Flying insects usually have two pairs of wings made of chitin • Flight has allowed for movement worldwide and wide variety of habitats

32. Subphylum Uniramia • Metamorphosis: process of changing shape and form • 2 types: incomplete and complete • Incomplete metamorphosis: gradual change with nymph immature forms • Nymphs lack sexual organs and wings and usually look similar to the adult form • Complete metamorphosis: dramatic change with larval stage and pupa

33. Insect Communication • Use sound, visual, chemical, and other types of signals • Most communication is for mating • Sound: crickets chirping by rubbing legs together; cicadas buzz by vibrating special membranes on their abdomens • Visual cues: fireflies lighting up • Chemical signals: pheromones used for alarm or alerting other insects and for mating

34. Insect Societies • Ants, bees, termites, and some of their relatives form complex associations called societies • Societies work together for the benefit of the whole group • Can have more than 7 million individuals • Castes: groups of individuals performing a certain job or role in the society (queen, workers, drones, etc)

35. Classification for Subphylum Uniramia • Centipedes: Class Chilopoda • Millipedes: Class Diplopoda • Insects: Class Insecta • Order Orthoptera: Crickets, grasshoppers, locusts • Order Isoptera: termites • Order Hymenoptera: bees, wasps, and ants • Order Lepidoptera: butterflies and moths • Order Diptera: true flies • Order Coleoptera: beetles • Order Hemiptera: true bugs • Order Anoplura: human louse (lice) • Order Odonata: dragonflies • Order Dictyoptera: cockroaches and mantids