Transcript Phylum Mollusca - Plymouth State University

Phylum Mollusca
Attributes of the molluscs
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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
Classes
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Monoplacophora
Polyplacophora
Gastropoda
Bivalvia
Cepahalopoda
Scaphopoda
Monoplacophora
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Neopilina-Missing links=
Architype==theoretical construct
Homeobox genes
Polyplacophora
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Chitons
Chitin--a complex mucopolysaacharide
Pieces of eight=shell is in eight pieces
Foot looks segmental
Paired gills in the mantle cavity
Gastropoda
• All mollusk characteristics
• Shell
– Simple
– Coiled shell
– Lacking
• Torsion
– Veliger
– Walter Garstang
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
Kinds of cephalopods
• Nautiloids
• Chamber Nautilus
– The Chambered Nautilus Poem
• Squid (calamari) shell reduced replaced by
chitinous pen
• Cuttlefish
• octopus
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
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