Mollusca Cephalopoda Nautiloids Nautilus – Shell with chambers Coleoids

1. Mollusca • Cephalopoda • Nautiloids • Nautilus – Shell with chambers • Coleoids • Octopuses – Eight arms, no shell; Cryptic • Squids – Shell reduced to pen made of chitin • Cuttlefishes – Carbonate shell • Siphon – Directs water released from mantle cavity • Highly mobile predators • Streamlined body (coleoids) • Large eyes • Complex nervous system • Closed circulatory system** • Shell reduced or absent (Why?) • Type of shell affects prey selection • Foot modified as arms and tentacles bearing suckers

2. Fig. 9-15 Fig. 9-16

4. Mollusca • Cephalopoda • Ink sac for defense • Chromatophores, iridophores: Facilitate color change video Fig. 9-17 Fig. 9-18

5. Mollusca • Cephalopoda • Reproduction: Dioecious; internal fertilization • Courtship behavior common • Male transfers spermatophore to female • Females sometimes guard benthic eggs • Often semelparous Squid eggs

6. Mollusca • Cephalopoda • Most massive invertebrates • Giant squid (Architeuthis) may be >15 m long!!

7. Mollusca • Polyplacophora (Chitons) • Mostly graze algae on rocky shorelines • Occupy home scar when not foraging • Scaphopoda (Tooth shells) • Predators on foraminifera and juvenile bivalves • Most common in deep water • Monoplacophora • Rediscovered in 1952 • Some repeated organs (pre-segmentation?) • Possible indication of relationship to Annelida

9. Fig. 9-6

10. Arthropoda • Most species of any phylum (1 million+) • Ubiquitous • Segmented, bilaterally symmetrical body • Jointed appendages • Exoskeleton made of chitin • Growth requires molting • Chelicerata (subphylum) • Crustacea (subphylum) • Contains majority of marine arthropod species • 150,000+ described species • Exoskeleton often hardened with CaCO3 • Gills + two pairs of antennae (sensory)

11. Arthropoda • Chelicerata • Terrestrial: spiders, ticks, mites, scorpions • Marine: horseshoe crabs, sea spiders • Merostomata (Horseshoe crabs) (class) • 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”) • Reproduce on beaches at high tide; eggs buried

12. Fig. 9-31

13. Arthropoda • Chelicerata • Pycnogonida (sea spiders) (class) • 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 • Males carry eggs (very unusual for marine inverts)

14. Fig. 9-32

15. Arthropoda • Crustacea • Mandibulates (paired mandibles) • Body regions: head, thorax, abdomen • Head and thorax may be fused (cephalothorax) • Two pairs of sensory antennae • Other appendages differ between groups

16. Crustacean Anatomy Fig. 9-33

17. Molting Fig. 9-34

18. Arthropoda • Crustacea • Decapoda (order) • Crabs, true shrimp, lobsters • Most species in Crustacea (~10,000) • Scavengers/Predators/Both • 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 • Largest crustaceans • Lobster > 42 lbs • Crab > 13 feet “tall”

20. Arthropoda • Crustacea • Decapoda (order) • Crabs, true shrimp, lobsters • Most species in Crustacea (~10,000) • Scavengers/Predators/Both • 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 • Largest crustaceans • Lobster > 42 lbs • Crab > 13 feet “tall”