I.I. MolluscaMollusca

B.B. BivalviaBivalvia• Laterally compressedLaterally compressed• Two-valved shellTwo-valved shell• No headNo head• No radulaNo radula• Some have muscular foot for burrowing (Some have muscular foot for burrowing (How?How?))• Gills used for suspension feeding (active) & Gills used for suspension feeding (active) &

respirationrespiration• Water enters and leaves through Water enters and leaves through siphonssiphons

• Some anchor to substrate with Some anchor to substrate with byssal threadsbyssal threads• Largest mollusk (giant clam)Largest mollusk (giant clam)• Shipworms (boring – use shells as rasps)Shipworms (boring – use shells as rasps)• Common Common fouling organismsfouling organisms• Oysters – Produce pearlsOysters – Produce pearls• Scallops – Swim!Scallops – Swim!

I.I. MolluscaMollusca

B.B. BivalviaBivalvia• Laterally compressedLaterally compressed• Two-valved shellTwo-valved shell• No headNo head• No radulaNo radula• Some have muscular foot for burrowing (Some have muscular foot for burrowing (How?How?))• Gills used for suspension feeding (active) & Gills used for suspension feeding (active) &

respirationrespiration• Water enters and leaves through Water enters and leaves through siphonssiphons

• Some anchor to substrate with Some anchor to substrate with byssal threadsbyssal threads• Largest mollusk (giant clam)Largest mollusk (giant clam)• Shipworms (boring – use shells as rasps)Shipworms (boring – use shells as rasps)• Common Common fouling organismsfouling organisms• Oysters – Produce pearlsOysters – Produce pearls• Scallops – Blue eyes, Scallops – Blue eyes, SwimSwim!!

I.I. MolluscaMollusca

C.C. CephalopodaCephalopoda1.1. Octopuses – Eight arms, no shell; CrypticOctopuses – Eight arms, no shell; Cryptic2.2. Squids – Shell reduced to Squids – Shell reduced to penpen made of made of chitinchitin3.3. Cuttlefishes – Carbonate shellCuttlefishes – Carbonate shell4.4. Nautilus – Shell with chambersNautilus – Shell with chambers• Highly mobile predatorsHighly mobile predators

• Large eyesLarge eyes• Complex nervous systemComplex nervous system• Closed circulatory systemClosed circulatory system****• Shell reduced or absent (Shell reduced or absent (Why?Why?))

• Type of shell affects prey selectionType of shell affects prey selection• Foot modified as arms and tentacles bearing suckersFoot modified as arms and tentacles bearing suckers• SiphonSiphon – Directs water released from – Directs water released from mantle cavitymantle cavity

• Ink sac for defenseInk sac for defense

Fig. 7.24

I.I. MolluscaMollusca

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 (segmentation?)• Possible indication of relationship to

Annelida

II.II. ArthropodaArthropoda

• Most species of any phylum (1 million+)Most species of any phylum (1 million+)• UbiquitousUbiquitous

• Segmented, bilaterally symmetrical bodySegmented, bilaterally symmetrical body• Jointed appendagesJointed appendages• ExoskeletonExoskeleton made of chitin made of chitin• Growth requires Growth requires moltingmolting

• Crustacea (subphylum)Crustacea (subphylum)• Contains majority of marine arthropod speciesContains majority of marine arthropod species

• 150,000+ described species150,000+ described species

• Exoskeleton often hardened with CaCOExoskeleton often hardened with CaCO33

• Gills + two pairs of antennae (sensory)Gills + two pairs of antennae (sensory)

II.II. ArthropodaArthropoda

A.A. Copepoda (Copepods)Copepoda (Copepods)• Extremely abundant and important Extremely abundant and important

planktonplankton• Among most abundant animals on earthAmong most abundant animals on earth• Benthic forms also importantBenthic forms also important

• Important primary consumers of Important primary consumers of phytoplanktonphytoplankton

• Some parasitic formsSome parasitic forms

Fig. 7.28

Fig. 15.7

Herbivorous vs. Predatory Copepod