I.Mollusca B.Bivalvia Laterally compressedLaterally compressed Two-valved shellTwo-valved shell No headNo head No radulaNo radula Some have muscular foot for burrowing (How?)Some have muscular foot for burrowing (How?) Gills used for suspension feeding (active) & respirationGills used for suspension feeding (active) & respiration Water enters and leaves through siphonsWater enters and leaves through siphons Some anchor to substrate with byssal threadsSome anchor to substrate with byssal threads Largest mollusk (giant clam)Largest mollusk (giant clam) Shipworms (boring – use shells as rasps)Shipworms (boring – use shells as rasps) Common fouling organismsCommon fouling organisms Oysters – Produce pearlsOysters – Produce pearls Scallops – Swim!Scallops – Swim!

I.Mollusca B.Bivalvia Laterally compressedLaterally compressed Two-valved shellTwo-valved shell No headNo head No radulaNo radula Some have muscular foot for burrowing (How?)Some have muscular foot for burrowing (How?) Gills used for suspension feeding (active) & respirationGills used for suspension feeding (active) & respiration Water enters and leaves through siphonsWater enters and leaves through siphons Some anchor to substrate with byssal threadsSome anchor to substrate with byssal threads Largest mollusk (giant clam)Largest mollusk (giant clam) Shipworms (boring – use shells as rasps)Shipworms (boring – use shells as rasps) Common fouling organismsCommon fouling organisms Oysters – Produce pearlsOysters – Produce pearls Scallops – Blue eyes, Swim!Scallops – Blue eyes, Swim!Swim

I.Mollusca C.Cephalopoda 1.Octopuses – Eight arms, no shell; Cryptic 2.Squids – Shell reduced to pen made of chitin 3.Cuttlefishes – Carbonate shell 4.Nautilus – Shell with chambers Highly mobile predatorsHighly mobile predators Large eyesLarge eyes Complex nervous systemComplex nervous system Closed circulatory system**Closed circulatory system** Shell reduced or absent (Why?)Shell reduced or absent (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 Siphon – Directs water released from mantle cavitySiphon – Directs water released from mantle cavity Ink sac for defenseInk sac for defense

Fig. 7.24

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 (segmentation?) Possible indication of relationship to Annelida

II.Arthropoda 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 Exoskeleton made of chitinExoskeleton made of chitin Growth requires moltingGrowth requires molting 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 CaCO 3Exoskeleton often hardened with CaCO 3 Gills + two pairs of antennae (sensory)Gills + two pairs of antennae (sensory)

II.Arthropoda A.Copepoda (Copepods) Extremely abundant and important planktonExtremely abundant and important plankton Among most abundant animals on earthAmong most abundant animals on earth Benthic forms also importantBenthic forms also important Important primary consumers of phytoplanktonImportant primary consumers of phytoplankton Some parasitic formsSome parasitic forms

Fig. 7.28

Fig Herbivorous vs. Predatory Copepod