I Arthropoda B Cirripedia Barnacles Active suspension feeders

I. Arthropoda B. 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? ? )

Fig. 7. 29

I. Arthropoda B. 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? ? )

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

Fig. 7. 30

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

I. Arthropoda E. Euphausiacea (Krill) • Laterally compressed • • Up to 10 cm long (usually smaller) Head 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)

I. Arthropoda F. 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

Fig. 7. 32

I. Arthropoda F. 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

Shediac, NB

Fig. 7. 37

I. Arthropoda G. 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”)

I. Arthropoda H. 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

Fig. 7. 39

II. 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

Fig. 7. 42

II. Echinodermata A. Asteroidea (Sea stars) - Class • • • Most species have five arms (some more) Tube feet on oral surface in ambulacral grooves Endoskeleton composed of Ca. CO 3 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

Heliaster helianthus

Crown of Thorns Acanthaster planci

II. Echinodermata B. 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? ?

Amphipholis squamata