2 Phylum Mollusca gastropods, bivalves,cephelapods 3 GENERAL BODY REGIONS1. head- with “brain” or sense organs2. visceral mass- contains internal organs3. foot- muscular part of body
3 Class Gastropoda (stomach-footed) Soft body in CaCO3 shell secreted by mantleBody is bilaterally symmetricalVentral muscular foot for locomotionRadula- rasping tongue, ribbon of small teeth used to feed on algae“breathe” through gills
6 Head-Foot RegionThe radula is a rasping, protrusible feeding structure found in most molluscs (not bivalves).Ribbon-like membrane with rows of tiny teeth.
7 Class GastropodaThe shell of a gastropod is always one piece – univalve – and may be coiled or uncoiled.The apex contains the oldest and smallest whorl.Shells may coil to the right or left – this is genetically controlled.
8 Class GastropodaEarly gastropods had a planospiral shell where each whorl lies outside the others.BulkyConispiral shells have each whorl to the side of the preceding one.UnbalancedShell shifts over for better weight distribution.
9 Class GastropodaMany snails can withdraw into the shell and close it off with an operculum.
10 ABALONE SNAILS LIMPETS CONCH NUDIBRANCH (sea slugs) gastropods that have lost their shellCONE SNAIL (car nivorous)
11 Class bivalvia Clams, oysters, mussels Laterally compressed body enclosed in two shells(valves) joined at a hinge, controlled by strong musclesGills used for getting 02 and filter feedNo head or radula
12 CLAMS- use foot to burrow in sediment CLAMS- use foot to burrow in sediment. Uses siphon to draw in water for O2 and food.
13 Largest bivalve- giant clam up to 3ft in length! (Tridacna gigas)*symbiotic zooxanthella help its size
14 SCALLOPS- some can swim by ejecting water rapidly out siphon MUSSELS- not burrowers, secrete strong byssal threads to attach to surfacesOYSTERS- cement their shells to a hard surface, sometimes to other oystersSCALLOPS- some can swim by ejecting water rapidly out siphonGEODUCK
15 PEARL OYSTERS- when there’s an irritant or parasite in the mantle, shiny layers of nacre coats it to form pearl in some* Most pearls we encounter are cultured pearls
16 Class BivalviaScallops have a row of small blue eyes along the mantle edge.
17 Class Bivalvia Native freshwater clams in the U.S. are jeopardized. Of more than 300 species once present, 12 are extinct, 42 are endangered and 88 more are of concern.Sensitive to water quality changes,Zebra mussels are a serious exotic invader into the Great Lakes Region.
18 Class cephalopoda (“head-footed”) Octopuses, squids, cuttlefishActive lifestyles, agile swimmersComplex nervous system, eyes similar to oursReduction/loss of shellFoot is modified into tentacles/arms with suckers
19 Nautilus Last living type of externally-shelled cephalopod Don’t exhibit many other squid/octopus-like qualities“Swimming snail”
20 “Jet-propulsion” of water, controlled by flexible siphon, for quick movement Fans out body in defense
21 OCTOPUSES-8 long arms, lack shell, bite prey (crabs, lobsters, shrimp) with beak-like jawsDistract predators by emitting cloud of dark fluid produced by ink sac
22 SQUID- better swimmers, elongated body, two triangular fins, 8 arms and two tentacles w/suckers circling mouth, shell reduced to stiff pen
23 Colossal squid- largest invertebrate, hooks on tentacles GIANT SQUID: up to 60ft in length, teeth on suckers.
24 CUTTLEFISH: have calcified internal shell that helps in bouyancy and gives its shape (cuttle bone) Look like squid but have fin running along sides
25 CAMOUFLAGEChromatophores-Red, brown, yellow pigments under skin controlled by musclesLight reflectors under skinMuscles able to change texture