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Exploring Molluscs: Characteristics and Diversity

Dive into the diverse world of molluscs, from their segmented body structures to the unique attributes of each class. Discover the fascinating features of molluscs such as trochophore larvae, shell composition, and specialized organs. Learn about Monoplacophora, Gastropoda, Bivalvia, Cephalopoda, and Scaphopoda, each with distinct characteristics and adaptations. Uncover the wonders of molluscs through this educational exploration.

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Exploring Molluscs: Characteristics and Diversity

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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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