A1260943007VtAOc

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subclass Opistobranchia
class Scaphopoda
class Polyplacophora
subclass Pulmonata
(nudibranchs, sea slugs, bubble shells,
pteropods, sea angels, sea hares...)
(tusk shells)
class Cephalopoda
(chitons)
class Gastropoda
(terrestrial snails, tree snails, garden snails,
pond snails, escargot, land slugs...)
PHYLUM MOLLUSCA
subclass Prosobranchia
order Archaeogastropoda
order Mesogastropoda
class Bivalvia
(limpets, abalone, keyhole limpets...)
order Neogastropoda
Keith Hiscock
(periwhinkles, conches, slipper shells, cowries,
tritons, moon snails...)
(nautilus, squid, cuttlefish, octopus)
(clams, mussels, scallops, jingle shells,
oysters, shipworms...)
(cone snails, oyster drills, dogwinkles,
whelks...)
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• Images on previous slide
• scaphopod (Antalis pretiosum) shell occupied by
  a hermit crab (Orthopagurus minimus). Photo by
  R. Shimek. http//www.rshimek.com/Scaph1.htm
• scallop (Placopecten magellanicus) from the Gray
  Museum Slide Collection. http//tolweb.org/tree?
  groupMolluscacontgroupBilateria
• chiton (Tonicella lineata) by E. Eugenia Patten.
  http//tolweb.org/tree?groupPolyplacophoracontgr
  oupMollusca
• squid (Loligo pealei) by David Remsen.
  http//tolweb.org/tree?groupMolluscacontgroupBi
  lateria
• silver cloud nudibranch by P. Crawford D.
  Giberson http//tolweb.org/tree?groupGastropoda
  contgroupMollusca
• limpet by P. Crawford. http//tolweb.org/tree?gro
  upGastropodacontgroupMollusca
• pulmonate snail http//tolweb.org/tree?groupGast
  ropodacontgroupMollusca
• mesogastropod (Littorina littorea)
  http//www.marlin.ac.uk/index2.htm?demo/Litlit.htm
  
• naogastropod (Conus marmoreus, the Marble Cone)
  by Giuseppe Mazza. http//www.cpsc.ucalgary.ca/Res
  earch/bmv/papers/shells.sig92.pdf

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An idealized mollusc, internal anatomy
From Kozloffs Invertebrates (1990)
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THE MANTLE AND THE MANTLE CAVITY variations on a
theme
the mantle secretes the shell the mantle cavity
is also the site for excretion in most
molluscs the mantle cavity houses the gills
(ctenidia, etc.) ...in chitons and
"archaegastropods", the mantle cavity is in the
rear of the animal - consequences for sediment
clogging the gills and, hence, a limitation to
hard surfaces ...in "mesogastropods" and
"neogastropods", torsion brings the mantle
cavity (and the gills) to the anterior, thus
reducing the problem of clogging ...in bivalves,
the mantle cavity becomes the filtering cavity
- their (mainly) stationary lifestyle makes
clogging a non-issue ...in cephalopods, the
mantle cavity becomes a jet propulsion
system ...and in terrestrial molluscs, the
mantle cavity becomes a lung!
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the stages of torsion
http//online.sfsu.edu/biol240/Labs/ lab_18mollus
cs/Pages/cephalopods.html
(some) snails have lungs too the apple snail
Asolene (Pomella) megastoma
bivalve anatomy
S. Gesquiere
1. lung opening 2. lung
lung close-up
modified from Kozloff's Invertebrates (1990)
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circulation
clams blood acts as hydraulic system to extend
the foot for burrowing cephalopods
well-developed heart, closed circulatory
system, relatively high blood pressures
abalone have a fairly well-developed delivery
system, despite their open circulation
foot 66 of body weight, 27 cardiac output
digestive gland 6 of weight, 13 of
output
(
)
http//www.heptune.com/cutfish.html
http//www.abalone.net/guide/ab_flt01.htm
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A COMPARATIVE VIEW OF EYES
from K. Schmidt-Nielsen Animal Physiology (1997).
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NERVOUS SYSTEMS non-cephalopod molluscs -
variable ladder-like system in chitons
multiple ganglia in many gastropods
well-developed brain in many sea slugs
WB Rudman
JA Pechenik (2000) Biology of the Invertebrates
the sea hare (Aplysia californica)