ZOO 115 Invertebrate Zoology

Mollusca

Mollusca – Classes

Monoplacophora Aplacophora Polyplacophora Gastropoda Bivalvia Scaphopoda Cephalopoda

animaldiversity.ummz.umich.edu/site/resources/Grzimek_inverts/Monoplacophora/Laevipilina_antarctica.jpg/medium.jpg

Mollusca – Class Monoplacophora

Resemble the generalized mollusc

Small (3 mm), flattened molluscs that inhabit deep water

Present in the Cambrian period – thought to be extinct until 1952

Single shellwww.manandmollusc.net/advanced_introduction/Images/Monoplacophora2.gif

Foot

Gills

Anus

Mouth

MantleMantle Cavity

http://www.labsis.usc.es/workshop/images/common/2.jpg

Mollusca – Class Aplacophora

~ 300 species Small benthic dwellers

between 200-7000m Shell-less

Secrete calcareous spicules on epidermis

Foot reduced or absent No eyes, tentacles,

statocysts, or nephridia

www.manandmollusc.net/advanced_introduction/aplac.html

Mantle Cavity

Gills

Pedal groove or foot

Mouth

Mollusca – Class Polyplacophora

~800 sp Ancient (since late

Cambrian) Lives in rocky-

intertidal region Has series of

plates for a shell. It is an herbivore

(except for one species)

http://www.ucd.ie/cobid/chitons/glossary_images/2002a0404131-c.jpg

http://www.ucd.ie/cobid/chitons/glossary_images/2002a0404135-b.jpg

Mollusca – Class Polyplacophora

Mollusca – Class Gastropoda Marine and terrestrial 2nd largest class in

animal kingdom Hard shell (most)

Mollusca – Class Gastropoda variety

Mollusca - Class Gastropoda Herbivores and

predators. Has a radula Hard shell (most) Well developed

head and cephalic tentacles

Locomotion – peristalsis of foot.

http://www.pirx.com/gallery/albums/mollusks/radula.jpg

/www.ling.helsinki.fi/~simon/gallery/snails

Mollusca – Class Gastropoda Anatomy

Mollusca – Class Gastropoda - foot

How can it do both?

/www.sfu.ca/~msr/Papers/BISC/images/nucelladesiccation

Columellar muscle

Tarsos muscle

Columellar muscle Retracts head and foot

into shell Extends head and foot Twists foot

Tarsos muscle Bottom of foot and edges Locomotion Prey capture Molding of eggs

No fluid filled hemocoel

Mollusca – Class Gastropoda Shell Coiling

http://www.cartage.org.lb/en/themes/Sciences/Paleontology/Paleozoology/FossilMollusks/AboutAmmonites/enroulement.jpg

http://www.cartage.org.lb/en/themes/Sciences/Paleontology/Paleozoology/FossilMollusks/AboutAmmonites/enroulement.jpg

http://content.answers.com/main/content/wp/en/a/a1/Snail-WA_edit02.jpg

http://etc.usf.edu/clipart/25100/25194/shell_25194_lg.gif

PlanospiralUncoiled

Whorl

http://www.palaeos.com/Invertebrates/Molluscs/Gastropoda/Images/Bellerophon.jpg

http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/gastropo/Diagrams/tort.gif

Torsion

http://www.weichtiere.at/images/weichtiere/schnecken/torsion.gif

180◦ counterclockwise rotation of visceral mass

Anus position

Gill position

WHY?

Torsion - WHY?

Larval theory – allows foot to be brought up into shell

Torsion - WHY?

Adult theory – allows for better

ventilation of mantle cavity and gills

Places osphridium anteriorly

May help increase efficiency of creeping with a coiled shell

Problem from torsion

Sanitation Slits or holes to

accommodate waste

Unidirectional flow of water

http://eebweb.arizona.edu/collections/Fishes/Invertebrate%20Slide%20Photos/Invertebrate%20Photos/Abalone%201.jpg

http://www.mesa.edu.au/friends/seashores/images/limpet_under.gif

Class Gastropoda - Diversity

Subclass – Prosobranchia Order Archeogastropoda Order Mesogastropoda Order Neogastropoda

Subclass Ophistobranchia Subclass Pulmonata

Molecular evidence indicates that these classifications are no longer valid!

Subclass Prosobranchia -

Usually with a spirally coiled shell (whorl)

Mantle cavity anterior Osphridium (not shown) Gills Anus Nephridiopore (not

shown)

http://snugglynoodles.com/images/haeckel/Haeckel_Prosobranchia.jpghttp://www.nmfs.noaa.gov/pr/images/invertebrates/blackabalone_anatomy.jpg

Order Archeogastropoda

Primative Herbivores

Radula has numerous teeth in transverse rows

1-2 bipectinate gills Mantle cavity without siphon Sexes separate

Order Archeogastropoda

Abalone Keyhole

limpets Limpets*

http://www.anth.ucsb.edu/faculty/glassow/RAMP/abalone.jpghttp://www.marlin.ac.uk/imgs/Species/Mollusca/o_diogra.jpg

* Order Patellogastropoda

http://www.marietta.edu/~biol/biomes/images/shores/shield_limpet_6150.jpg

Order Mesogastropoda

http://www.maier-kern.com/wordpress/wp-content/uploads/2006/02/DSC02058.JPG

Vermetidae

Hydrobia

Turritellidae

http://elrinconmarinosgasteropodos.iespana.es/Fotos%20coleccion/Cerithidae.jpg

Cerithidae

http://www.shellmuseum.org/Shells2/alatus2.jpg

Strombidae

Janthinidae

http://elrinconmarinosgasteropodos.iespana.es/Fotos%20coleccion/Janthinidae.jpg

http://www.seashell-collector.com/beginners/CAPULIDAE.jpg

Capulidaehttp://www.seashell-collector.com/beginners/CALYPTRAEIDAE.jpg

Calyptraeidae

http://www.eumed.net/malakos/Images/Carinaria_mediterranea.jpg

Carinaridaehttp://www.timespub.tc/fileadmin/user_upload/featured/Summer2004/Shell%2028.jpg

Naticidae

http://www.seashell-collector.com/beginners/CYPRAEIDAE.jpg

Cypraeidae

http://www.seashell-collector.com/beginners/OLIVIDAE.jpg

Olividae

http://www.dkimages.com/discover/previews/965/50007882.JPG

Tonnidae

http://seashellplace.com/catalog/images/BullmouthCameoHelmet.jpg

Cassidae

http://www.seashell-collector.com/beginners/FICIDAE.jpg

Order Mesogastropoda

Operculum present Radula with seven

teeth/row Only left gill –

unipectinate One atrium One nephridium

http://oceanica.cofc.edu/shellguide/pics/univalve.gif

Order Neogastropoda

Order Neogastropoda

Entirely marine Radula with 3 or fewer

teeth per row One gill One atrium One nephridim

Order Neogastropoda

Mollusca – Order Neogastropoda Cone snail