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1 2 Lophophorates • Ciliated Lophophore- feeding structure • Hollow lophophore tentacles are projections of the coelom (respiratory) • Surrounds mouth 3 4 Phylum Bryozoa • “Ectoprocta” • 4000 species, both FW and Marine • Colonial– Zoecium – Jack-in-the-box – operculum 5 Phylum Brachiopoda 6 • 325 extant, 12,000 extinct • Two calcareous shells: Top/bottom, not right/left 1 7 Phylum Mollusca: snails, slugs, chitons, 8 clams, octopus and squid “HAM” • Trend toward rounder body: low SA/vol ratio • Lack of segmentation (except Neopilina) • Hypothetical Molluscan ancestor – Mantle and mantle cavity, shell – Muscular foot: sensory and locomotory – Visceral Mass • Cephalization: sensory and feeding • Gills (most) • Complete GI w/ glands, radula • Open circ. system*: heart and haemocoel • Metanephridium • Separate sexes 9 10 ! The trochophore larva Shell and Mantle 3 layers 1. Periostracum 2. Prismatic 2nd larval stage-Veliger larva of snail 11 3. Nacreous 12 Radula 2 13 14 Class Monoplacophora Class Scaphopoda 15 Class Polyplacophora: chitons • • • • • 16 Cryptochiton stelleri- Gumboot Chiton 600 living species, mostly intertidal Most similar to ancestral mollusc Broad-footed herbivores 8 overlapping plates Very little cephalization: no eyes or tentacles, small head w/ radula Class Gastropoda: snails, slugs, limpets • Largest molluscan class, 40,000 species • Mobile: Herbivores and Carnivores • 3 important changes from ancestral mollusc – Greater cephalization: affects sensory and locomotion – Asymmetrical spiral shell: portable protection – Torsion: realignment of body with shell • Feeding strategies and specializations • Gills or “lungs” 17 18 Torsion- do you see a problem? (and de-torsion) 3 19 20 Class Bivalvia: clams • Laterally compressed w/dorsal hinge • Very large mantle cavity: use of gills for respiration and suspension (filter) feeding Pulmonate gastropodsmantle cavity modified into lung – Incurrent and excurrent siphons • No radula or distinct head present • Pearls: require inner nacreous layer 21 22 Ctenidia Internal Anatomy Highly modified for respiration AND feeding Water/Food path 23 24 Burrowing Locomotion Cl. Cephalopoda: nautilus, squid, octopus • 650 species, extinct members include Ammonites (65 mya) • Predators • Swimming lifestyle: jet propulsion • Reduced or absent shell • Closed circulatory system • Cephalization: sensory, movement, learning • Foot gives rise to funnel • Arms that are probably derived from the molluscan head • Chitinous beaks • Direct development (larvae?) • Cephalopod eye: convergence 4 25 26 27 28 Squid Internal Anatomy 29 30 Giant Squids Architeuthis 5 31 6