Arthropoda Cirripedia (Barnacles) Active suspension feeders (filter feeders)

1. Arthropoda • Cirripedia (Barnacles) • Active suspension feeders (filter feeders) • Use feathery cirri(modified swimming appendages) • Sessile (attached to surfaces) • Fouling organisms (boats, whales) • Resemble mollusks superficially • Some parasitic forms • Simultaneous hermaphrodites • Internal fertilization (How??)

2. Fig. 7.29

3. Arthropoda • Cirripedia (Barnacles) • Active suspension feeders (filter feeders) • Use feathery cirri (modified swimming appendages) • Sessile (attached to surfaces) • Fouling organisms (boats, whales) • Resemble mollusks superficially • Benthic forms also important • Some parasitic forms • Simultaneous hermaphrodites • Internal fertilization (How??)

5. Arthropoda • Amphipoda (Amphipods) • Laterally compressed • Generally small (< 2 cm), but larger in deep ocean • Widespread distribution • Generally free living • Important scavengers • Often highly mobile • Some sedentary forms • Diverse lifestyles • Brood young

6. Fig. 7.30

10. Arthropoda • Isopoda (Isopods) • Dorsoventrally compressed • Generally small (< 2 cm), but larger in deep ocean • Related to terrestrial pill bugs • Widespread distribution • Generally free living • Important scavengers • Often highly mobile • Some parasitic forms • Brood young

12. Arthropoda • Euphausiacea (Krill) • Laterally compressed • Up to 10 cm long (usually smaller) • Head and anterior segments fused to form distinct carapace • Widespread distribution • Important primary consumers and predators • Important prey for larger consumers • Keystone species in some ecosystems (Southern Ocean) • Aggregate in schools • May be immense (450 sq km x 200 m @ >1000 m-3)

14. Arthropoda • Decapoda (Crabs, Lobsters, Shrimps) • Most species in Crustacea (~10,000) • Scavengers/Predators/Both • Largest crustaceans • Lobster > 42 lbs • Crab > 10 feet “tall” • Five pairs of walking legs • First pair usually modified as claws for feeding/defense • Well-developed carapace = cephalothorax • Rest of body = abdomen • Lobsters, shrimp – Usually laterally compressed • Tail/Abdomen behind thorax • Crabs – Usually dorsoventrally compressed • Tail/Abdomen curled underneath thorax

15. Fig. 7.32

16. Arthropoda • Decapoda (Crabs, Lobsters, Shrimps) • Most species in Crustacea (~10,000) • Scavengers/Predators/Both • Largest crustaceans • Lobster > 42 lbs • Crab > 10 feet “tall” • Five pairs of walking legs • First pair usually modified as claws for feeding/defense • Well-developed carapace = cephalothorax • Rest of body = abdomen • Lobsters, shrimp – Usually laterally compressed • Tail/Abdomen behind thorax • Crabs – Usually dorsoventrally compressed • Tail/Abdomen curled underneath thorax

19. Shediac, NB

20. Fig. 7.37

21. Arthropoda • Merostomata (Horseshoe crabs) • Not true crabs • Five living species • Distinctive, horseshoe-shaped carapace • Benthic predators/scavengers on clams and small invertebrates • No jaws - Grind food with bristles on walking legs (must be walking to “chew”)

23. Arthropoda • Pycnogonida (Sea spiders) • Superficially resemble spiders • Mouth at end of large proboscis (unusual) • Carnivores • Feed on sea anemones, hydrozoans, other soft inverts • No respiratory or excretory systems • Digestive system extends into legs

24. Fig. 7.39

26. Echinodermata • Radial symmetry (secondary) • Bilateral symmetry in larvae • Pentaradial symmetry in adults • Oral/aboral - No anterior/posterior, dorsal/ventral • Complete digestive tract (except Ophiuroidea) • Endoskeleton • Covered with layer of tissue • Water vascular system • Unique to echinoderms • Tube feet extended by pressure from ampullae • Tube feet used for locomotion, feeding, sensory functions • Connected to exterior through madreporite

27. Fig. 7.42

28. Echinodermata • Asteroidea (Sea stars) - Class • Most species have five arms (some more) • Tube feet on oral surface in ambulacral grooves • Endoskeleton composed of CaCO3 plates • Flexible skeleton – permits movement • Aboral surface often covered with pedicellariae • Small claws used for grooming surface • Predators • Feed on bivalves, snails, barnacles • Pry shells of bivalve apart and insert stomach

30. Heliaster helianthus

31. Crown of Thorns Acanthaster planci

32. Echinodermata • Ophiuroidea (Brittle stars, Serpent stars) • More species (~2000) than any other class • Arms long and very flexible • May resemble writhing snakes • Tube feet lack suckers (used for feeding) • Cryptic – Usually not in open areas • Scavengers/Detritivores • Particles collected by tube feet and passed to mouth • May suspension feed by climbing on taller objects (e.g. sponges) • Some have eyes and produce bioluminescence • Why??

33. Amphipholis squamata