Download Mollusca and Annelida

Mollusca
Soft bodied animals
Mollusca General Info
• 150,000 known species
• Most mollusks are marine, but some live in
fresh water environments
• Mollusks are soft-bodied animals that are
sometimes protected by a hard shell
Symmetry in Mollusca
• In the beginning of the
life cycle of a mollusk,
bilateral symmetry is
present, but this may
be lost by adulthood as
they have spiral
development
Body Development in Mollusks
• 3 main parts: muscular
foot, a visceral mass, and a
mantle
• The muscular foot is used
for movement
• The visceral mass contains
most of the internal organs
• The mantle is a fold of
tissue that secretes the
shell if present, covers the
visceral mass
• The shell secreted by the
mantle is made of CaCO3
Movement
• In Polyplacophora,
Gastropoda, and
Bivalvia, a muscular
foot is used for
locomotion
• In Cephalopods,
siphon made from
the mantle allows jet
propulsion
Germ Layers and Coelom
• Open circulatory system, where the body
cavity is a blood-filled hemocoel filled with
hemophyll (blood and lymph between
organs)
Life Cycle/Reproduction
• Starts with a ciliated
larva, otherwise known
as a trochophore
• No true segmentation
unlike Annelids
• Normal sexual
reproduction is present,
although some are
hermaphrodites
• Most have external
fertilization
Specialized Tissue
• The radula is a tongue-like structure that scrapes up
food and is modified into a beak in the octopus
• The mantle cavity is a water-filled chamber that houses
the gills, anus, and excretory pores
• Torsion is a process in Gastropoda where one set of
muscles grows faster than the other, which creates the
shell to grow in a spiral pattern
Chiton (Polyplacophora)
Octopus
(Cephalopoda)
Snail
(Gastropoda)
Squid (Cephalopoda)
Scallops (Bivalvia)
Mollusk behavior
http://www.youtube.com/watch?v=nHVoV0MVwSc nudibranch
http://www.youtube.com/watch?v=zsScH4TJ7NA chiton
http://www.youtube.com/watch?v=5oExwxkuT_c octopus camoflauge, beak, and feeding
http://www.youtube.com/watch?v=9azBDt0kik&feature=PlayList&p=EF6646ECD09DBAB3&index=0&playnext=1 flexible octopus body
http://www.youtube.com/watch?v=T8cf7tPoN5o&feature=PlayList&p=EF6646ECD09DBAB3&index
=1&playnext=2&playnext_from=PL octopus intelligence
http://www.youtube.com/watch?v=k_coXZq05xY swimming clam
http://www.youtube.com/watch?v=UUNsrkV_KIY&feature=related burrowing clam
http://www.youtube.com/watch?v=XbOwjE8EkSw&feature=PlayList&p=859B17D0EA1926B2&playnex
t=1&index=2 chambered Nautilus