The Animal Clade
Extant
deuterostomia
protostomia
acoelomates
radiata
pseudocoelomates
bilateria
parazoa
eumetazoa (true tissues)
loss of chloroplast, colonial organization
Ancestral Choanoflagellate
coelomates
This cladogram omits
several smaller animal
phyla!
Animals
Domain Eukarya
Kingdom Animalia
Phylum Mollusca
35,000 species making this the second-largest phylum of Animalia
Polyplacophora: chitons
The most-primitive mollusc has 8
valves (plates) protecting its soft
tissues beneath. The chiton foot
attaches to rocks and the animal
uses its radula to scrape organic
material from the rock surfaces.
http://www.dec.ctu.edu.vn/sardi/mollusc/images/chiton.jpg
http://www.birdsasart.com/red%20Chiton.jpg
After working hard to remove the “suck rock” organism from the rock,
the ventral surface of the chiton shows the obvious mollusc features.
gills
foot
mouth
(radula inside)
http://faculty.clintoncc.suny.edu/faculty/Michael.Gregory/files/Bio%20102/Bio%20102%20lectu
res/animal%20diversity/protostomes/chiton_ventral_surface.jpg
The chiton has multiple eyes. Some are just light-sensitive spots.
The primary eyes are of a lens-type. Many chiton species lack eyes.
http://nighthawk.tricity.wsu.edu/museum/ArcherdShellCollection/Illustrations/Chiton_Eyes.JPG
This cartoon shows a longitudinal slice of a chiton with the three
principal parts: foot (locomotion or attachment), visceral mass
(internal organs), and mantle (secretes valves).
dorsal aorta
gonad
valve plates
heart
pericardial cavity
(coelom)
ventricle
hemocoel
auricle
radula
mantle
mouth
anus
foot
digestive stomach
nephridium
nephridiopore
gland
ventral
gonopore
nerve cord
(not shown)
As for all other molluscs, chitons use a radula to scrape their
food from environmental surfaces. Below is a radula removed
from a chiton mouth.
http://www.abc.net.au/quantum/stories/Chiton_teeth_m97943.jpg
Gastropoda: snails and relatives (slugs)
Snails have a single spiral-shaped valve (univalve)
Slugs and nudibranchs have lost this feature.
optical tentacle
shell
eye
foot
gonopore
sensory tentacles
http://www.zetnet.co.uk/~pm/photos/snail.jpg
http://coris.noaa.gov/glossary/trochophor_larv_186.jpg
And now for a look inside our gastropod mollusc…
Trochophore
larva:
Quic kTime™ and a
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Veliger larva:
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http://www.zetnet.co.uk/~pm/photos/snail.jpg
http://people.bu.edu/veliger/veliger.jpeg
The shell obviously provides a hard covering for the visceral mass.
The snail shown here is a pulmonate, with a vascularized mantle
cavity serving as a lung. Vascularizing this led to loss of the gills in
most gastropods.
The gastropods, are clearly hermaphroditic, and some are self-fertile.
This is a slug, its mantle is reduced to a “saddle” and does not
secrete a shell. The other features of the snail are all present.
optical tentacles
sensory
tentacles
mantle
foot
skirt
http://people.ucsc.edu/~cpncrunk/banana_slug_06.jpg
Here is the longitudinal section of an optical tentacle.
The eye of the slug is a lens-type eye.
1. digitate ganglion
2. collar cell
3. olfactory nerve
4. tentacle retractor muscle
5. lateral processed cell
6. lateral oval cell
retinal cell:
7. optic nerve
11. microvilli
8. accessory retina
12. pigment cell
9. lens
13. light sensitive cell
10. retina
http://www.byteland.org/slugfest/banana_slug_mark_bonnington.jpg
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
http://members.tripod.com/arnobrosi/eye.gif
Here is a micrograph of a longitudinal section of a snail eye
The tentacle
has all of the
optical,
sensory, and
neural parts
we expect for
vision.
lens
olfactory
ganglion
retina
optic
nerve
olfactory
nerve
http://www.az-microscope.on.ca/images/eye.jpg
The tentacle
has all of the
sensory, and
neural parts
we expect for
chemical
sensation too.
The sensory
tentacles
have these
features too.
The slug shows the pneumostome in the mantle for breathing.
pneumostome
foot
skirt
mantle
optical tentacles
sensory tentacles
http://www.nawwal.org/~mrgoff/photojournal/2003/winspr/pictures/05-17slug2.jpg
These two slugs are showing mating behavior.
The slugs are dangling on a slime thread and
grip each other with their feet.
http://members.optushome.com.au/awnelson/davidavid/slug/
The slugs evert their
reproductive organs out
through the gonopore.
The organs unite and
spermatophores are
exchanged.
Sperm are stored in a
spermatheca for a week
or more. Syngamy and
deposition of zygotes
occurs later.
http://www.arnobrosi.com/3.jpg
http://www.arnobrosi.com/6.jpg
Bivalva: bivalves
This group includes the
clams, oysters, mussels,
and scallops.
Their body is typical
mollusc too, but with
two hinged valves
(shells)
http://users.actrix.com/littlejn/bivalve.jpg
http://www-biol.paisley.ac.uk/biomedia/
graphics/jpegs/aopercu.jpg
Here is a cartoon of a lateral view of the foot, visceral mass and mantle
Adductor muscles to hold the valves together.
Bivalves have gills rather than lungs.
Their incurrent siphons take in plankton lodging in mucus.
The mucus
laden particles
gather on the
gills (palps)
and enter the
mouth.
The mouth
lacks the
radula.
http://bio.classes.ucsc.edu/bio136/molluscs/bivalve/bivalvia.html
This cartoon is shows a plane of section perpendiular to the previous one.
The foot can push a
bivalve through
sediments.
The food-trapping
gills are used for
gas exchange.
The heart pumps
the blood into the
hemocoel bathing
the tissues. It goes
through the gills
for gas exchange.
The blood then
returns to the heart.
hinge and ligament
shell
heart
nephridium
intestine
mantle
gonad
gills
foot
Nephridia cleanse the blood of nitrogenous waste.
Here are three different molluscs. Between the valves of the
bivales the mantle fringe is quite visible. With the valves ajar, the
bivalve can carry out its filter feeding. If you swim nearby, the
bivalve adductor muscles snap the valves shut.
http://www.photogg.de/frokt02/10-10-scallop.jpg
How does the bivalve know you are swimming by? Eyes!
http://www.nmfs.noaa.gov/prot_res/images/other_spec/scallop_eyes.jpg
Here are close-ups of the bivalve eye and a cartoon of its structure.
This gives the impression of being somewhat intermediate
between a lens-type and a pinhole-type eye.
http://www.eyedesignbook.com/ch3/fig3-05aBG.jpg
http://nighthawk.tricity.wsu.edu/museum/ArcherdShellCollection/Illustrations/Pecten_Eye.JPG
Tridacna crocea
Gymnodinium microadriaticum
QuickTime™ and a
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QuickTime™ and a
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http://reef.geddis.org/p/1425-clam.jpg
http://reef.geddis.org/p/0846-clam.jpg
Cephalopoda: the chambered nautilus, squid, and octopus
The
nautilus
has
gastropod
features
operculum
eye
tentacles
http://www.worldstart.com/wallpaperjpg/1ws-%20Nautilus.jpg
valve
Pinhole eye of Nautilus
Advantage: simple, detailed
Disadvantage: low light collection
retina
pinhole
This Caribbean reef squid is small. The giant squid is the largest
invertebrate animal known…17 meters long…2 tons!
fin
eye
mantle
chromatophores
Smaller arms surround the mouth
Two grasping tentacles
http://www.macalester.edu/geology/wirth/tilefish/cozumel/image/squid.jpg
Contrary to the
filename, this is a
Humboldt squid.
It is certainly
large, but is not
the giant squid.
Between the
tentacles part of
the beak is
shown.
The eyes face the
man’s knee and
elbow.
The mantle is in
his lap and the fin
is over his
shoulder.
http://www.seacamsys.com/Scott-Giant%20Squid-1.jpg
The squid eye is a lens-based
eye, rather than a pinhole eye.
Is this cartoon correct, based
upon your dissection of the
squid in class?
retina
http://www.biol.lu.se/funkmorf/vision/dan/pupil1.jpg
lens
Advantage: collects more light
Another cephalopod is the octopus.
It obviously has eight tentacles surrounding the mouth…no, duh!
This one is obviously swimming.
http://www.pmel.noaa.gov/vents/nemo/logbook/images/sep7-octopus-lores.jpg
Here is another swimming octopus. The idea of cephalopod (headfoot) is shown nicely here. Behind one tentacle the siphon is
showing the basis for jet-action locomotion among cephalopods.
http://www.pithagorio.net/Mat/octopus%202.jpg
What kind of eye does an octopus have?
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Squid eye
http://www.cas.vanderbilt.edu/bsci111b/eye/octopus-eye.jpg
http://www.notcot.com/images/vert.octopus.baby.ap-thumb.jpg
Note: I am fairly certain that the
animal shown above on the right
is a squid, rather than an octopus:
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http://scubadive.tv/photographers/pics/pulpo.jpg
http://www.spc.org.nc/coastfish/Countries/Tokelau/octopus.jpg
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http://artstream.ucsc.edu/fdm170a/joanne/slug.gif
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http://www.wildlifebcnp.org/wtphotos/smalls/Ian%20Towle%20-%20slug.jpg
http://www.smartassglass.com/images/Slug-Big-Hands-Gold.jpg
gastropod
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http://neogirlfl.tripod.com/sitebuildercontent/sitebuilderpictures/slug.jpg
http://home.att.net/~onefin/images/clam.jpg
bivalve
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