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Phylum Mollusca

Phylum Mollusca. Attributes of the molluscs. Segmental Trochophore larvae Head, foot and body component Shell is secreted by mantle Periostracum Prismatic Mother of pearl==nacreous Radula in the mouth cavity Have pairs of feather like gills--ctenidial gills Paired excretory organs.

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Phylum Mollusca

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  1. Phylum Mollusca

  2. Attributes of the molluscs • Segmental • Trochophore larvae • Head, foot and body component • Shell is secreted by mantle • Periostracum • Prismatic • Mother of pearl==nacreous • Radula in the mouth cavity • Have pairs of feather like gills--ctenidial gills • Paired excretory organs

  3. Classes • Monoplacophora • Polyplacophora • Gastropoda • Bivalvia • Cepahalopoda • Scaphopoda

  4. Monoplacophora • Neopilina-- • Missing links= • Architype==theoretical construct • Homeobox genes

  5. Polyplacophora • Chitons • Chitin--a complex mucopolysaacharide • Pieces of eight=shell is in eight pieces • Foot looks segmental • Paired gills in the mantle cavity

  6. Gastropoda • All mollusk characteristics • Shell • Simple • Coiled shell • Lacking • Torsion • Veliger • Walter Garstang

  7. Cephalopoda • Head is surround by the foot in the form of arm/tentacles • Radula is present but vestigial, chitin jaws • Muscular mantle and siphon allows for jet propulsion • Paired ctenidial gills • Have a partially closed circulatory system with visceral and gill hearts • Very efficient digestive system

  8. Kinds of cephalopods • Nautiloids • Chamber Nautilus • The Chambered Nautilus Poem • Squid (calamari) shell reduced replaced by chitinous pen • Cuttlefish • octopus

  9. Bivalvia (Pelcypoda) • Shell of two halves • Mantle is often produced into a siphon • Incurrent/excurrent • Gill is sheet-like (lamellibranch) • Foot may be extensible or small or lacking • Gooeyduck, mussel, scallop • Most are filter feeders • Osphraedia in incurrent siphon detect the nature of the incoming stream

  10. Scaphopoda • Shell elongate, hollow tube • Foot works similar to that of bivalves only circular in nature, with tentacle-like structures around • Lacks gills • Mantle cavity tubular • Wampum

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