Download Phylum Mollusca

http://www.palaeos.com/Invertebrates/Molluscs/Images/mollusc_classes.jpg
Phylum Mollusca
• Triploblastic- 1st with coelom (small cavity
space around various organs- for molluscsheart and gonads)
• Bilateral symmetry (3 body parts: head-foot,
visceral mass, and mantle)
• Visceral mass contains all organs
• Mantle is outer layer and may secrete a shell
• Mouth has radula structure which is a belt
with rows of curved teeth on a tongue-like
structure called an odontophore.
http://www.science.mcmaster.ca/Biology/Harbour/SPECIES/BIVALVIA/IMAGES/ORGAN1.GIF
http://upload.wikimedia.org/wikipedia/commons/thumb/4/45/Radula_diagram3.png/300px-Radula_diagram3.png
Radula and odontophore
Molluscan shell loss and reduction…
http://images.google.com/imgres?imgurl=http://www.andrewgray.com/essays/cepshell.gif&imgrefurl=http://www.andrewgray.com
/essays/molluscs.htm&usg=__pHYWvKpK6tG9esL_b7xpQx8mQ8w=&h=234&w=312&sz=7&hl=en&start=2&um=1&tbnid=S2drmzyr1D
DJZM:&tbnh=88&tbnw=117&prev=/images%3Fq%3Dmollusc%2Bloss%2Bof%2Bshell%26hl%3Den%26um%3D1
Class Gastropoda
• Largest class of mollusks! (Snails, slugs, and
limpets)
• Undergo torsion in early development (body
twisting 180°)
– 3 advantages to torsion:
• Head enters shell first to escape predators
• Anterior opening allows clean water to enter mantle
• Sensory organ around head help snail to be more
sensitive to stimuli
*some snail go through detorsion (twist 180then untwist 90)
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Most shells asymmetrical
Feed by scraping with radula
Cilia in digestive tract as well as on foot
Some gastropods have a siphon =rolled extension of
the mantle
Respiration is by gills in aquatic snails, and by gas
exchange through mantle in land snails
Open circulatory system with heart
Hydraulic skeleton of blood
Well developed sensory structures (tentacles with
eyes)
Most marine snails dioecious, others monoecious
Eggs laid in external fertilization, deposited in moist
environments
http://www.marietta.edu/~biol/
biomes/images/shores/shield_li
mpet_6150.jpg
Limpets
http://www.guardianseries.co.uk/resources/images/23155
4/?type=display
http://oceanexplorer.noaa.gov/explorations/0
4fire/logs/april14/media/limpet_eggs_600.jpg
Barnacles- NOT
mollusks!
http://www.mtkembla-e.schools.nsw.edu.au/gallery/galleryimages/barnacles.jpg
http://www.restaurantwidow.com/images/20
07/04/27/barnacles.jpg
Class Bivalvia
• 2nd largest mollusk class (clams, oysters, mussels,
scallops)
• 2 halves = valves
• Oldest part of shell = umbo (near anterior)
• Hinges of protein to keep shell closed
• Pearls made from secretions of mantle (best
pearls come from pacific oysters)
• Loss of head and radula
• Folded Gills for resipration
• Filter feed from water: cilia in bivalve moves food
along food grooves toward mouth; labial palps
sort food
• Open circulatory system
• Nervous system with ganglia (only some
species have eyes- scallops)
• Most dioecious, few monoecious
• External fertilization- most brood young
http://oregonstate.edu/dept/ncs/photos/oysters.jpg
http://blueoceannotes.files.word
press.com/2009/08/oysters.jpg
http://www.pac.dfo-mpo.gc.ca/science/speciesespeces/shellfish-coquillages/geopath/Images/intro1.jpg
http://www.barrierreefaustralia.com/IMAGEGALLERY/giant-clam.jpg
http://community.adn.com/sites/community.adn.com/files/i
mages/Weathervane%20scallops%20-%20ASMI.preview.jpg
http://cookingoysters.co.uk/wp-admin/images/preparing%20mussels.jpg
http://wednesdaychef.typepa
d.com/photos/uncategorized/
mussels_1.jpg
http://oceangrow.septentriones.com/data/upi
mages/scallop.jpg
Class Cephalopoda
• Octopus, squid, cuttlefish, nautilus
• Most complex of phylum mollusca
• Foot modified into tentacles/arms and funnel for
locomotion
• Head is in line with visceral mass
• Mantle has radial and circular muscles
• Possess jaws and radula (octopus inject venom)
• Locate prey by sight and capture with tentacles
(mostly fish, crustaceans, and other
invertebrates)
• Nautilus is the only cephalopod with an
external shell
• Cuttlefish and squid have internal skeletons
– Cuttlefish = Cuttlebone
– Squid = Pen
• The octopus has no shell
• Closed circulatory system
• Pigment cells (chromatophores) to change
color
• Complex nervous system- large brain/ganglia
– Eyes similar to vertebrates
• Ink glands behind anus
• Dioecious
• Reproduction by male placing spermatophore
into female near oviduct; eggs are laid singly
or in strings and usually attach to substrate.
Cuttlefish
http://www.oceanfutures.org/spongebob/gallery/images/gallery_pim432c3.jpg
http://fundiesvatheists.lefora.com/composition/atta
chment/c441ea1fa6c330e0c9bc72ff5c5e7d54/19297
0/ComCuttlefish9.jpg
Squid
http://images.google.com/imgres?imgurl=http://nea
torama.cachefly.net/images/2008-04/giantsquid.jpg&imgrefurl=http://www.neatorama.com/20
08/04/30/colossal-squid-at-te-papa-museum-in-newzealand/&usg=__1XokKm5sRqqkWnKCQx86OvA5f8I=
&h=374&w=500&sz=46&hl=en&start=31&um=1&tbn
id=qXUY7pVNM1cWgM:&tbnh=97&tbnw=130&prev
=/images%3Fq%3Dsquid%26ndsp%3D20%26hl%3De
n%26sa%3DN%26start%3D20%26um%3D1
http://images.google.com/imgres?imgurl=http://news.nationalgeographic.com/news/2007/02/images/070222squid_big.jpg&imgrefurl=http://news.nationalgeographic.com/news/2007/02/070222-squidpictures.html&usg=__b5FBOMpbizi4ZbuOxcWpzGr9uRI=&h=454&w=461&sz=59&hl=en&start=28&um=1&tbnid=1G9OtH5
NzdUoQM:&tbnh=126&tbnw=128&prev=/images%3Fq%3Dsquid%26ndsp%3D20%26hl%3Den%26sa%3DN%26start%3D20%
26um%3D1
http://www.scuba-equipmentusa.com/marine/FEB04/images/Octopus_tetricus.jpg
Octopus
http://www.smh.com.au/ffximag
e/2005/02/12/octopus_wideweb
__430x308.jpg
http://media.smithsonianmag.com/images/deep4.jpg
http://www.bbc.co.uk/devon/content/images/2007/12/06/blue_ringed_octopus_465x310.jpg