I. Mollusca

C. Cephalopoda1. Nautiloids

a. Nautilus – Shell with chambers

2. Coleoidsa. Octopuses – Eight arms, no shell; Crypticb. Squids – Shell reduced to pen made of chitinc. 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. 9-15

Fig. 9-16

I. Mollusca

C. Cephalopoda• Ink sac for defense• Chromatophores,

iridophores: Facilitate color change video

Fig. 9-17

Fig. 9-18

I. Mollusca

C. Cephalopoda• Reproduction: Dioecious; internal fertilization

• Courtship behavior common• Male transfers spermatophore to female• Females sometimes guard benthic eggs• Often semelparousSquid eggs

I. Mollusca

C. Cephalopoda• Most massive

invertebrates• Giant squid

(Architeuthis) may be >15 m long!!

I. Mollusca

D. Polyplacophora (Chitons)• Mostly graze algae on rocky shorelines• Occupy home scar when not foraging

E. Scaphopoda (Tooth shells)• Predators on foraminifera and juvenile bivalves• Most common in deep water

F. Monoplacophora• Rediscovered in 1952• Some repeated organs (pre-segmentation?)• Possible indication of relationship to Annelida

Fig. 9-6

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 CaCO3

• Gills + two pairs of antennae (sensory)

II. Arthropoda

A. Chelicerata• Terrestrial: spiders, ticks, mites, scorpions• Marine: horseshoe crabs, sea spiders

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. Arthropoda

A. Chelicerata2. 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. Arthropoda

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. 9-33

Crustacean Anatomy

Fig. 9-34

Molting

II. Arthropoda

B. Crustacea1. 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. Arthropoda

B. Crustacea1. 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”