The Animal Clade Chordata Ancestral Choanoflagellate Cnidaria Hemichordata Echinodermata Extant deuterostomia Arthropoda Annelida Mollusca protostomia

The Animal Clade

Chordata

Ancestral Choanoflagellate

Cnidaria

Hemichordata

EchinodermataExtant

deuterostomia

Arthropoda

Annelida

Mollusca

protostomia

coelomates

Nematoda

Rotifera

pseudo-coelomates

Platyhelminthes

acoelomates

radiatabilateria

eumetazoa (true tissues)

Porifera

parazoa

loss of chloroplast, colonial organization

This cladogram omits several smaller animal phyla!

Animals

Domain EukaryaKingdom AnimaliaPhylum Mollusca

35,000 species making this the second-largest phylum of Animalia

http://www.dec.ctu.edu.vn/sardi/mollusc/images/chiton.jpghttp://www.birdsasart.com/red%20Chiton.jpg

Polyplacophora: chitonsThe 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://faculty.clintoncc.suny.edu/faculty/Michael.Gregory/files/Bio%20102/Bio%20102%20lectures/animal%20diversity/protostomes/chiton_ventral_surface.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

footmouth(radula inside)

http://nighthawk.tricity.wsu.edu/museum/ArcherdShellCollection/Illustrations/Chiton_Eyes.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.

mouth

radula

valve plates

gonadheart

pericardial cavity(coelom)

mantle

anusfootdigesti

ve gland

nephridiumstomach

ventral nerve cord(not shown)

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).

auricle

ventricle

nephridioporegonopore

hemocoel

dorsal aorta

http://www.abc.net.au/quantum/stories/Chiton_teeth_m97943.jpg

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.zetnet.co.uk/~pm/photos/snail.jpg

Gastropoda: snails and relatives (slugs)Snails have a single spiral-shaped valve (univalve)Slugs and nudibranchs have lost this feature.

foot

shell

eye

optical tentacle

sensory tentaclesgonopore

http://www.zetnet.co.uk/~pm/photos/snail.jpg

And now for a look inside our gastropod mollusc…

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.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

http://coris.noaa.gov/glossary/trochophor_larv_186.jpg

Trochophore larva:



http://people.bu.edu/veliger/veliger.jpeg

Veliger larva:

http://people.ucsc.edu/~cpncrunk/banana_slug_06.jpg

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.

mantlefoot

skirt

optical tentaclessensory

tentacles

http://members.tripod.com/arnobrosi/eye.gif

Here is the longitudinal section of an optical tentacle. The eye of the slug is a

lens-type eye.

retinal cell:11. microvilli12. pigment cell13. light sensitive cell



http://www.byteland.org/slugfest/banana_slug_mark_bonnington.jpg

1. digitate ganglion2. collar cell3. olfactory nerve4. tentacle retractor muscle5. lateral processed cell6. lateral oval cell7. optic nerve8. accessory retina9. lens10. retina

http://www.az-microscope.on.ca/images/eye.jpg

Here is a micrograph of a longitudinal section of a snail eye

olfactoryganglion

olfactorynerve

lens

retina

opticnerve

The tentacle has all of the optical, sensory, and neural parts we expect for vision.

The tentacle has all of the sensory, and neural parts we expect for chemical sensation too.The sensory tentacles have these features too.

http://www.nawwal.org/~mrgoff/photojournal/2003/winspr/pictures/05-17slug2.jpg

pneumostome

optical tentacles

sensory tentacles

mantlefoot

skirt

The slug shows the pneumostome in the mantle for breathing.

http://www.arnobrosi.com/3.jpg

http://www.arnobrosi.com/6.jpg

http://members.optushome.com.au/awnelson/davidavid/slug/

These two slugs are showing mating behavior.The slugs are dangling on a slime thread and grip each other with their feet.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://users.actrix.com/littlejn/bivalve.jpg

http://www-biol.paisley.ac.uk/biomedia/

graphics/jpegs/aopercu.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://bio.classes.ucsc.edu/bio136/molluscs/bivalve/bivalvia.html

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.

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.

Nephridia cleanse the blood of nitrogenous waste.

hinge and ligament

nephridium

mantle

shell

gills

foot

gonad

intestine

heart

http://www.photogg.de/frokt02/10-10-scallop.jpg

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.nmfs.noaa.gov/prot_res/images/other_spec/scallop_eyes.jpg

How does the bivalve know you are swimming by? Eyes!

http://nighthawk.tricity.wsu.edu/museum/ArcherdShellCollection/Illustrations/Pecten_Eye.JPG

http://www.eyedesignbook.com/ch3/fig3-05aBG.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://reef.geddis.org/p/1425-clam.jpg





http://reef.geddis.org/p/0846-clam.jpg

Tridacna crocea Gymnodinium microadriaticum

http://www.worldstart.com/wallpaperjpg/1ws-%20Nautilus.jpg

Cephalopoda: the chambered nautilus, squid, and octopus

valve

operculum

tentacles

eye

The nautilus has gastropod features

Pinhole eye of NautilusAdvantage: simple, detailed

Disadvantage: low light collectionretina

pinhole

http://www.macalester.edu/geology/wirth/tilefish/cozumel/image/squid.jpg

This Caribbean reef squid is small. The giant squid is the largest invertebrate animal known…17

meters long…2 tons!

Two grasping tentacles

Smaller arms surround the mouth

mantlefin

eye chromatophores

http://www.seacamsys.com/Scott-Giant%20Squid-1.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.biol.lu.se/funkmorf/vision/dan/pupil1.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

lens

Advantage: collects more light

http://www.pmel.noaa.gov/vents/nemo/logbook/images/sep7-octopus-lores.jpg

Another cephalopod is the octopus.It obviously has eight tentacles surrounding the mouth…no, duh!This one is obviously swimming.

http://www.pithagorio.net/Mat/octopus%202.jpg

Here is another swimming octopus. The idea of cephalopod (head-foot) is shown nicely here. Behind one tentacle the siphon is showing the basis for jet-action locomotion among cephalopods.

http://www.cas.vanderbilt.edu/bsci111b/eye/octopus-eye.jpg

Note: I am fairly certain that the animal shown above on the right is a squid, rather than an octopus:

Squid eye

http://scubadive.tv/photographers/pics/pulpo.jpg

What kind of eye does an octopus have?



http://www.notcot.com/images/vert.octopus.baby.ap-thumb.jpg



http://www.spc.org.nc/coastfish/Countries/Tokelau/octopus.jpg

http://artstream.ucsc.edu/fdm170a/joanne/slug.gif





http://www.smartassglass.com/images/Slug-Big-Hands-Gold.jpgQuickTime™ and aTIFF (Uncompressed) decompressor


http://www.wildlifebcnp.org/wtphotos/smalls/Ian%20Towle%20-%20slug.jpg



http://neogirlfl.tripod.com/sitebuildercontent/sitebuilderpictures/slug.jpg



http://home.att.net/~onefin/images/clam.jpg

bivalve

gastropod

Documents

The Animal Clade Chordata Ancestral Choanoflagellate Cnidaria Hemichordata Echinodermata Extant deuterostomia Arthropoda Annelida Mollusca protostomia