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 TIFF (Unc om pres s ed) dec ompres s or are needed to s ee t his pict ure. Veliger larva: QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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 TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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? QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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: QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. http://scubadive.tv/photographers/pics/pulpo.jpg http://www.spc.org.nc/coastfish/Countries/Tokelau/octopus.jpg QuickTi me™ and a T IFF (Uncompressed) decompressor are needed to see thi s pi cture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. http://artstream.ucsc.edu/fdm170a/joanne/slug.gif QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. http://www.wildlifebcnp.org/wtphotos/smalls/Ian%20Towle%20-%20slug.jpg http://www.smartassglass.com/images/Slug-Big-Hands-Gold.jpg gastropod QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. http://neogirlfl.tripod.com/sitebuildercontent/sitebuilderpictures/slug.jpg http://home.att.net/~onefin/images/clam.jpg bivalve QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.