Mollusks Odyssey Expeditions

2 Phylum Molluska Means “soft body” Includes clams, snails, sea slugs, and octopus Freshwater, marine and terrestrial Most have external shell of calcium carbonate Jason Buchheim

3 General Characteristics Posses a mantle –Circulates water through organism –Feeding, propulsion, and/or shell production –Gills or lungs found in mantle cavity Posses a muscular foot –Used to crawl with –Tentacles in cephalopods Posses a radula –Tongue bearing teeth used for feeding (like a conveyor belt) Radula

4 Classes Class Monoplacophora Class Polyplacophora Class Aplacophora Class Gastropoda Class Bivalvia Class Scaphopoda Class Cephalopoda

5 Class Monoplacophora Relic class Many fossilized mollusks belong to this class Less than 20 extant (living) species Single cap-like shell Creeping foot Found in deep water (2000 to 7000m)

6 Class Polyplacophora Chitons Oval in shape Eight over lapping plates Creeping foot that adheres tightly to rocky surfaces Mostly inhabit rocky intertidal zones Feed on algae and other organisms on the rocks

7 Class Aplacophora Worm-like Small (<5mm) No shell, have calcareous spicules in mantle Inhabit deep water (200 to 7000m) Creep or burrow Very little known Ventral View

8 Class Gastropoda Largest class of mollusks (30,000 species) Snails and snail-like organisms Well developed head with tentacles and eyes Most possess single coiled asymmetrical shell Most crawl with foot but some swim with it

9 Gastropod Subclasses Subclass Prosobranchia Subclass Opisthobranchia Subclass Pulmonata

10 Subclass Prosobranchia Mantle cavity anterior Marine Shelled Many have operculum (hard disc attached to the foot that covers the opening to the shell for protection) Some use mantle as camouflage Includes conchs, whelks, cones, abalone, and drills Herbivores and carnivores

11 Subclass Opisthobranchia Mostly marine Shell reduced or lacking Mantle cavity on right side, posterior, or even lacking Some respire through skin or external gills Mantle generally colorful and ornate May have modified foot to swim with Typically few inches in length Includes sea hares, nudibranchs, sea slugs Herbivores and carnivores (have very specific diets)

12 Subclass Pulmonata Typically terrestrial Shelled (except slugs) Mantle cavity modified into lungs Includes terrestrial snails, freshwater snails and slugs Typically herbivores

13 Class Bivalvia Consists of two hinged shells or valves Gills used for filter feeding as well as respiration (water brought in and out by siphons while buried in sediment) The mantle of some contains tentacles and eye spots to detect movement. No head Second largest molluscan class (8,000 extant species) Freshwater and marine Includes cockles, mussels, oysters, scallops, and clams

14 Class Scaphopoda Tusk or tooth shell (looks like elephant’s trunk) Marine Single elongated tube-like shell. Burrowing Modified foot for digging Possess tentacles to capture interstitial (organisms found among sediment grains) 2-6 cm long

15 Class Cephalopoda Elongated Highly cephalized Well developed nervous system Foot modified into specialized arms and tentacles for prey capture Shell external, internal, or absent Includes nautilus, squid, octopus, and cuttlefish Propulsion created by expulsion of water from mantle cavity NOAA Jason Buchheim

16 Cephalopod Subclasses Subclass Nautiloidea Subclass Ammonidea Subclass Coleoidea

17 Subclass Nautiloidea Nautilus Only 4 extant species (most are extinct) Multi-chambered external shell Gas in chambers provides buoyancy (connected by central siphuncle canal and separated by septa) Siphuncle used to add or remove gas to chambers Many arms (~90) for prey capture

18 Subclass Ammonidea All members extinct Coiled, external, multi-chambered shells Complex septa with siphuncle found along outer axis of shell Index fossils

19 Subclass Coleoidea Squid, octopus, cuttlefish Internal or lacking shell Eight arms with suckers Squid and cuttlefish also have two tentacles for prey capture Ability to camouflage is exceptional Have large nerve cells used in research NOAA Jason Buchheim

20 Resources Barnes, Robert D. and Edward Ruppert. Invertebrate Zoology: Sixth Edition. Fort Worth: Saunders College Publishing, 1994 Humann, Paul and Ned Deloach. Reef Creature Identification: Florida Caribbean Bahamas. Florida: New World Publications, Inc., 2003 Kinsella, John, Drew Richardson and Bob Wohlers. Life on an Ocean Planet. California: Current Publishing Corp., 2006 Taylor, Walter K. and Robert L. Wallace. Invertebrate Zoology: A Laboratory Manual Sixth Edition. New Jersey: Prentice Hall, 2002