Invertebrates II: Mollusca, Arthropoda, Echinodermata, Chordata (non-vertebrate chordates)

1. Invertebrates II:Mollusca, Arthropoda, Echinodermata, Chordata (non-vertebrate chordates)

2. ©2004 Amanda Demopoulos I. Phylum Mollusca • More species (200,000+) than any other animal phylum except Arthropoda • Soft body – often protected by CaCO3 shell • Unsegmented, typically bilaterally symmetrical

3. BODY PLAN: • Head (eyes/sensory), visceral mass (organs), muscular foot • Mantle – covers visceral mass, secretes shell • Radula – Ribbon of small chitin teeth used in feeding • Gills (ctenidia-comb like) for gas exchange in mantle cavity Fig. 7.19

4. Radula – Ribbon of small chitin teeth used in feeding

5. I. Phylum Mollusca • Exceptions to basic plan • Bivalves lack radulas • Squids have internal shells • Octopuses have no shells • Reproduction (for some gastropods and bivalves) • 2 larval forms • Trocophore – looks similar to annelid larva • Veliger – ciliated, wing-like, with shell Veliger Trocophore

6. ©2004 Amanda Demopoulos • Phylum Mollusca • 4 classes A. Class Gastropoda (=stomach foot) • Largest, most common, most diverse group (40K-75K sp) • Coiled mass of vital organs=visceral mass enclosed by a shell • Snails • Limpets • Abalones • Nudibranchs – lose shell in larval stage • Ventral creeping foot • Diet • Many vegetarian (scrape algae off rocks with radula) • Some predatory • Prey on bivalves, worms, fishes, sponges

7. I. Phylum Mollusca A. Class Gastropoda • Torsion : during late veliger stage, twisting of visceral mass 180º, counter-clockwise, resulting in coiled shell • Operculum : leathery, trap door • *Drawing: radula slide, live lettuce slugs-order Sacoglossa, marine snails*

8. Abalones Snails Snails Snails

9. Nudibranchs

10. Anterior adductor muscle Posterior adductor muscle Valves Mantle Foot I. Phylum Mollusca Giant clam B. Class Bivalvia (=2 valved) • Laterally compressed • Hinged, 2-valved shell – (oysters, clams, mussels, scallops) muscles keep closed • No head , no radula • Sedentary lifestyle • Some have muscular foot for burrowing (e.g., clams) • Gills used for suspension feeding (active) & respiration • Water enters and leaves through siphons (incurrent and excurrent) • Some anchor to substrate with byssal threads (e.g., mussels) • Scallops – Swim! (repeated clapping of valves) • *Drawing-Scallop shell, live flame scallop

11. I. Phylum Mollusca C. Class Cephalopoda (=head footed) • Octopuses (5 cm – 9 m)– no shell; Cryptic, bite prey with beak-like jaw • Squid (giant ~ 1000 kg, 18 m) – Shell reduced to pen made of chitin • Cuttlefish – Carbonate shell=cuttlebone, aid in buoyancy • Nautilus – Shell with chambers (septa) filled with gas, buoyancy organ • Exclusively marine • Fast moving, highly mobile predators • Large eyes • Shell reduced or absent • Foot modified as arms and tentacles bearing suckers • Siphon – Directs water released from mantle cavity • Move by jet propulsion-move in any direction • Ink sac for defense-distraction • http://www.pbs.org/wnet/nature/octopus/

12. **Drawing-squid and nautilus** Phylum MolluscaClass Cephalopoda- Octopus and squid have beak-like jaws- Mouth is central among tentacles Squid 8 arms + 2 tentacles non-retractable w/suckers and hooks Octopus 8 arms, non-retractable w/ 2 rows of suckers Nautilus 60-90 suckerless tentacles Cuttlefish 8 arms + 2 tentacles, retractable w/ suckers, no hooks

13. eye 2 –extensible tentacle stalks fin mantle funnel tentacle clubs arm

14. I. Phylum Mollusca C. Class Polyplacophora (Many-plate-bearing=Chitons, 800 species) • Mostly graze algae on rocky shorelines • Exclusively marine • 8 overlapping plates • *drawing-chiton* D. Class Scaphopoda (=spade foot, Tusk shells) • Predators on foraminifera and juvenile bivalves • Most common in deep water, buried in sediment © Charlotte M. Lloyd

15. II. Phylum Arthropoda • Most species of any phylum (1 million+), 75% of all animals species described • Insects, spiders, centipedes, crabs, lobsters, shrimp, barnacles, etc. • Segmented, bilaterally symmetrical body • Jointed appendages • Exoskeleton made of chitin • Growth requires molting - defenseless • Body segments • Head, thorax, abdomen • Some groups have head and thorax fused = cephalothorax • Discuss 3 subphyla and representative classes

16. Subphylum Trilobitomorpha Class Trilobita • Marine • Extinct since 250 mya • Rich fossil history because of exoskeleton • Dorso-ventrally flattened • *drawing-trilobite fossil*

17. Subphylum Chelicerata A. Class Merostomata (=legs attached to mouth, Horseshoe crabs) • Not true crabs • Named for feeding appendages – chelicerae • Distinctive, horseshoe-shaped carapace • No antennae • Benthic predators/scavengers on clams and small invertebrates • No jaws - Grind food with bristles on walking legs (must be walking to “chew”) • Much of what we know understand about vision based on horseshoe crab eyes • Blood is used to test injectable pharmaceutical solutions for bacterial contamination • **drawing-horseshoe crab**

18. Subphylum Chelicerata B. Class Pycnogonida (= thick knees, Sea spiders) • All marine • Superficially resemble spiders • Mouth at end of large proboscis • Carnivores • Feed on sea anemones, hydrozoans, • other soft inverts • Legs much longer than body, more than 8 • *Drawing-sea spider* PHOTO: Bill Rudman

19. Subphylum Crustacea (40K species) • Contains majority of marine arthropod species • Gills + two pairs of antennae (sensory) • Larval forms – nauplius and zoea A. Class Copepoda (=oar foot, Copepods) • Extremely abundant holoplankton (always plankton) • Some live on/in substrates (benthos) • **Among most abundant animals on earth** • Important primary consumers of phytoplankton • Small << 1-2 mm • Some parasitic forms • *drawing-copepod slide*

20. Subphylum Crustacea B. Class Cirripedia (= hairy foot, Barnacles) • Active suspension feeders (filter feeders) • Use feathery cirri (modified swimming appendages) • Sessile (attached to surfaces-whales, piers) • Fouling organisms (boats, whales) • Resemble mollusks superficially – calcareous plates • *drawing-barnacle nauplii, cypris*

21. Subphylum Crustacea C. Class Malacostraca(=soft shell, 75% crustacean species-Discuss 4 Orders) 1. Order Amphipoda (Amphipods) beach hoppers, sand fleas, whale lice • Laterally compressed • Generally small (< 2 cm), but larger in deep ocean • Head and tail downward • Widespread distribution • Generally free living • Important scavengers • *drawing-Gammarus slide, Daphnia slide* ©2004 Amanda Demopoulos

22. Subphylum Crustacea C. Class Malacostraca 2. Order Isopoda (Isopods-rock lice, fish lice) • Dorsoventrally compressed • Generally small (< 2 cm), but larger in deep ocean • Related to terrestrial pill bugs • Widespread distribution • Generally free living • Important scavengers • Some parasites

23. Subphylum Crustacea C. Class Malacostraca 3. Order Euphausiacea (Krill) - holoplankton • 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 (whales, penguins, fish) • Keystone species in some ecosystems (Polar, Southern Ocean) • Aggregate in schools (billions of individuals) • *Drawing: euphausid (krill) specimens*

24. Subphylum Crustacea C. Class Malacostraca 4. Order Decapoda (=10 legs, Crabs, Lobsters, Shrimps) • Most species in Crustacea (~10,000) • Scavengers/Predators/Both • Largest crustaceans • Five pairs of walking legs (deca=10) • First pair usually modified as claws for feeding/defense • Well-developed carapace = cephalothorax • Rest of body = abdomen, tail • Laterally compressed, except crabs – abdomen under cephalothorax • *drawing-crab zoea slide, lobster

25. Fig. 7.30

26. Phylum Arthropoda Subphylum-Uniramia Class Insecta=Hexapoda (6 footed) • 1 million species described to date • Found in every known terrestrial + freshwater habitat, some marine except deep sea • Diversity attributable to • Feeding specialization • Dispersal capabilities • Predator-avoidance possibilities (flight) • *Drawing-insect leg types a) walking legs b) swimming legs

27. Phylum Echinodermata – • spiny skin • 6000 species • Sea lilies, feather stars, brittle stars, sea stars, sand dollars, sea urchins, sea biscuits, sea cucumbers • Radial symmetry • Pentaradial symmetry in adults • Oral/aboral • Endoskeleton = hard plates, ~95% calcium carbonate, covered by skin • Complete digestive, nervous systems, and reproductive organs • Regeneration • Water vascular system = internal hydraulic system • Unique to echinoderms • Tube feet (podia) extended by pressure from ampullae (muscular sacs) • Tube feet used for locomotion, feeding, sensory functions • Connected to exterior through madreporite (porous plate)

28. Phylum Echinodermata • Class Stelleroidea = a star A. Subclass Asteroidea (=star like, Sea stars) • 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 • *drawing-sea star, starfish young slide*

29. Crown of Thorns Acanthaster planci

30. Phylum Echinodermata • Class Stelleroidea B. Subclass Ophiuroidea (Brittle stars, Serpent stars) • Arms long and very flexible • May resemble writhing snakes • Tube feet lack suckers (used for feeding) • Central disk distinct • 1 Mouth, no anus • Cryptic – Usually not in open areas • Scavengers/Detritivores • Particles collected by tube feet and passed to mouth • (*drawing brittle star*)

31. III. Phylum Echinodermata C. Class Echinoidea (=spine like, Sea urchins, sea biscuits, sand dollars), (Echinus = Gr. Hedgehog) • Round, rigid test with movable spines and pedicellariae • Spines and tube feet used for locomotion • Tube feet in shallow ambulacral grooves (5 rows) along outside of test • Complete digestive system • Mouth on bottom, anus on top • Herbivores • Feed on seaweeds and seagrasses (especially drifting) plus attached encrusting organisms • Mouth includes Aristotle’s lantern (system of jaws and muscles used to bite off algae, other food from bottom) • *drawing-sea urchin, sand dollar*