Invertebrates Phylum Annelida

1. Invertebrates Phylum Annelida • Segmented Worms • segmentation allows specialization of system • Body Plan: Tube-within-a-tube • Body Systems • Digestion • Pharynx, esophagus, crop, gizzard, intestine, accessory glands • Musculatory • Longitudinal and circular muscles in each segment • Circulatory • Closed system with pumping hearts • Nervous system • brain, ventral nerve cord, and ganglia in each segment • Excretory system • nephridia in most segments

2. Annelidacont’d • Class Polychaeta • Largest class - marine worms • Have setae-bristles for anchoring worm or helping in locomotion • Arranged in bundles on parapodia • Swimming, gas exchange • Polychaetes are seasonal breeders • After fertilization, a trochophore larva develops-same larval type as molluscs

3. Annelidacont’d • Class Polychaeta cont’d • Representative Organisms • Clam worms-Nereis • Predators-eat crustaceans and other small animals • Tube worms • Tentacles that form a funnel-shaped fan • Sessile filter feeders

4. Polychaete diversity • Fig. 30.13

5. Annelidacont’d • Class Oligochaeta • Earthworms • Few setae per segment • No obvious head • Gas exchange across body wall • Feed on leaves and other organic matter • Food is drawn into mouth by muscular movements • Digestive tract has a large surface area • Typhlosole-expanded region on dorsal surface of intestine

6. Earthworm, Lumbricus • Fig. 30.14

7. Annelidacont’d • Class Oligochaetacont’d • Segmentation • Structure • External - evident by body rings • Internal - septa • Nervous System • Ventral nerve cord has ganglionic swellings in each segment • Lateral nerves extend from ganglions • Excretory • Paired nephridia in each segment • 1st funnel-like collects coelomic fluid • 2nd exits through body wall

8. Annelidacont’d • Class Oligochaeta cont’d • Segmentation cont’d • Circulation • Blood moves anteriorly through dorsal vessel • Enters aortic arches- “hearts” • Pump blood to ventral vessel • blood then moves posteriorly • Branches in each segment

9. Annelidacont’d • Class Oligochaeta cont’d • Reproduction in earthworms • Hermaphroditic • Male organs- testes, seminal vesicles, sperm ducts • Female organs-ovaries, oviducts, seminal receptacles • Worms lie parallel in opposite directions • Clitellum produces mucus to keep sperm moist • After separation, produces a slime tube which moves eggs and sperm together for fertilization • Slime tube then produces a cocoon

10. Annelidacont’d • Class Hirudinea • Leeches • Most live in freshwater • Most are ectoparasites- have suckers for feeding • Saliva contains hirudin-anticoagulant • Have same general body plan as other annelids • Lack setae • Each body ring has transverse grooves • Makes leech appear to have more segments

11. Invertebrates Phylum Arthropoda • Exoskeleton of chitin • Must undergo molting to allow growth • Exhibit jointed appendages • Walking, swimming, reproduction, eating, sensory reception • 3 body regions • Head, thorax, abdomen • Well-developed nervous system • Brain and ventral nerve cord • Sense organs-compound eyes, antennae

12. Arthropod diversity • Fig. 30.15

13. Phylum Arthropodacont’d. • Subphylum Crustacea • Barnacles, shrimps, lobsters, crabs, crayfish • Terrestrial - sowbug

14. Phylum Arthropodacont’d. • Subphylum Crustaceacont’d • Crayfish: Representative external structure • Fused cephalothorax • Head has compound eyes and 5 pairs of appendages • First 2 pairs are antennae, 3 pair are mouth parts • Thorax has 5 pair of appendages-walking legs • 1st walking leg has a pinching claw • Gills are situated above the walking legs • Abdomen- has swimmerets • Last 2 segments have uropods and telson

15. Phylum Arthropodacont’d. • Subphylum Crustacea cont’d • Crayfish: Representative internal structure • Digestive system • 2 part stomach, green glands for waste excretion • Vascular system • heart pumps blood with hemocyanin into hemocoel • Hemocyanin has blue pigment • Hemolymph flows around organs

16. Phylum Arthropodacont’d. • Subphylum Crustaceacont’d • Crayfish: Representative internal structure cont’d • Nervous system • Brain and ventral nerve cord with segmental ganglia • Sensitive hair like receptors on antennae • Mechanoreceptors: responds to physical stimuli • Chemoreceptors: sensitive to chemicals in the water • Reproduction • Sexes separate- sperm transfer by first pair of swimmerets • Ovaries open at base of third walking legs • After fertilization, eggs attach to swimmerets of female

17. Male crayfish, Cambarus • Fig. 30.16

18. Phylum Arthropodacont’d. • Subphylum Uniramia • Insects; largest and most diverse group • General structure • Head with pair of compound eyes or several simple eyes, a pair of antennae, mouthparts adapted to specific way of life • Thorax: 3 pairs of legs and wings if present • Abdomen: contains internal organs

19. Phylum Arthropodacont’d. • Subphylum Uniramiacont’d • Representative Organism: Grasshopper • 3rd pair of legs is adapted for jumping • 2 pairs of wings • Tympanum on side of first segment of abdomen • Ovipositor of females- for digging a hole in which to lay eggs.

20. Phylum Arthropoda cont’d. • Subphylum Uniramiacont’d • Grasshopper cont’d. • Internal organs • Digestive system-stomach, intestine, rectum, anus • Excretory system - Malpighian tubules • Uric acid-nitrogenous waste • Respiratory system-spiracles lead into trachae • Air pumped by contraction and relaxation of body wall • Circulatory system-heart pumps hemolymph into aorta, leads to a hemocoel • Hemolymph has no specialized pigment and is colorless

21. Phylum Arthropoda cont’d. • Subphylum Uniramiacont’d • Grasshopper cont’d. • Reproduction • Adapted to terrestrial life • Internal fertilization protects zygotes and gametes from drying • Penis inserted into female, sperm stored in seminal receptacle • Fertilized eggs are deposited into ground • Metamorphosis • change in form and physiology that occurs as a larva becomes and adult • Immature grasshopper called nymph

22. Female grasshoppers • Fig. 30.18

23. Phylum Arthropodacont’d. • Comparing Subphyla Uniramia and Crustacea • Grasshopper: terrestrial • Spiracles and trachae for gas exchange • O2 diffuses directly through to reach cells • Has tympanum for reception of sound • Use legs for hopping and wings for flying • Penis for passing sperm to female to prevent drying • Crayfish: aquatic • Crayfish gills for gas exchange • require oxygen-carrying pigment to carry oxygen to cells • Hair like receptors • Utilize uropods for swimming • Sperm passed to female, eggs carried externally.

24. Phylum Arthropodacont’d. • Subphylum Chelicerata • Arachnids: Spiders, ticks, scorpions, mites • Cephalothorax • 6 pairs of appendages • Chelicerae, pedipalps, and 4 pairs of walking legs • Abdomen contains internal organs • Ticks and mites are ectoparasites

25. Phylum Arthropodacont’d. • Subphylum Cheliceratacont’d • Representative Organism: Spiders • Narrow waist separates cephalothorax from abdomen • Fangs deliver poison to prey • Pedipalps sense and hold prey • Digestion: • Digestive juices released into prey, initial digestion is external • digested “broth” then is sucked into stomach • Gas Exchange • lamellae of inner body wall for gas exchange • “book lungs” • Silk glands for web-spinning

26. Arachnid diversity • Fig. 30.19