I. I.Mollusca C. C.Cephalopoda 1. 1.Nautiloids a. a.Nautilus – Shell with chambers 2. 2.Coleoids a. a.Octopuses – Eight arms, no shell; Cryptic b. b.Squids – Shell reduced to pen made of chitin c. c.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

Fig Fig. 9-16

I. I.Mollusca C. C.Cephalopoda Ink sac for defense Chromatophores, iridophores: Facilitate color change videovideo Fig Fig. 9-18

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

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

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

Fig. 9-6

II. II.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 CaCO 3 Gills + two pairs of antennae (sensory)

II. II.Arthropoda A. A.Chelicerata Terrestrial: spiders, ticks, mites, scorpions Marine: horseshoe crabs, sea spiders 1. 1.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

Fig. 9-31

II. II.Arthropoda A. A.Chelicerata 2. 2.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)

Fig. 9-32

II. II.Arthropoda B. B.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

Fig Crustacean Anatomy

Fig Molting

II. II.Arthropoda B. B.Crustacea 1. 1.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”

II. II.Arthropoda B. B.Crustacea 1. 1.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”