Chapter 7Chapter 7

Phylum MolluscaPhylum MolluscaClass BivalviaClass Bivalvia

Class GastropodaClass Gastropoda

Class CephalopodaClass Cephalopoda

http://www.zsm.mwn.de/mol/e/

ucmp.berkeley.edu

ucmp.berkeley.eduseawater.no

Xaxor.com

Phylum MolluscaPhylum Mollusca• Characteristics:Characteristics:

– More than 200,000 speciesMore than 200,000 species

– Name means "soft body”Name means "soft body”

– Basic body plan – head, muscular foot and visceral mass Basic body plan – head, muscular foot and visceral mass in most speciesin most species

home.sandiego.edu

General Anatomy of General Anatomy of MolluscsMolluscs– Mantle- secretes shell, waste disposal, sensory Mantle- secretes shell, waste disposal, sensory

reception, respirationreception, respiration

– Many have a shell of calcium carbonateMany have a shell of calcium carbonate

– Radula for grazing is unique to this groupRadula for grazing is unique to this group

– Some are deposit feeders, others carnivores, Some are deposit feeders, others carnivores, some use radula for scraping algae, encrusting some use radula for scraping algae, encrusting animals, etc. off substrates animals, etc. off substrates

– Well developed nervous systemWell developed nervous system

– Open circulatory systemOpen circulatory system

– Complete digestive systemComplete digestive system

– Sexual reproduction - Sexual reproduction - trochophoretrochophore larvae larvae develops into a develops into a planktonic veligerplanktonic veliger larvae larvae complete with shell (miniature version of adult)complete with shell (miniature version of adult)

General ReproductionGeneral Reproduction

fao.org

Class PolyplacophoraClass Polyplacophora

• ChitonsChitons• 800 species800 species

• All marineAll marine

• Dorsal shell of 8 platesDorsal shell of 8 plates

• Ventral muscular footVentral muscular foot

• Ventral mouth with radulaVentral mouth with radula

shells.tricity.wsu.edu

Class PolyplacophoraClass Polyplacophora

• ChitonsChitons• Mostly found in shallow water, coastal environments Mostly found in shallow water, coastal environments

of hard substrateof hard substrate

• Many graze on algae & small animals in marine Many graze on algae & small animals in marine intertidal zone (area between high and low tides)intertidal zone (area between high and low tides)

Class BivalviaClass Bivalvia– Clams, oysters, scallops, mussels, etc.Clams, oysters, scallops, mussels, etc.

– Two shells or Two shells or ““valvesvalves””

– Oldest part of the shell is called the umboOldest part of the shell is called the umbo

– Shell grows out from the umbo in concentric rings Shell grows out from the umbo in concentric rings

– No head presentNo head present

– No radula presentNo radula present

– Adductor muscles secure valves togetherAdductor muscles secure valves together

– Muscular foot used for burrowing in bottom and other Muscular foot used for burrowing in bottom and other locomotionlocomotion

– Water circulated with siphonsWater circulated with siphons

– Gills for respiration & food gathering (filter feeding)Gills for respiration & food gathering (filter feeding)

– Some species burrow, others attach to hard substrates Some species burrow, others attach to hard substrates via byssal threads, or grow attached to each other via byssal threads, or grow attached to each other

Class BivalviaClass Bivalvia

Class BivalviaClass Bivalvia

• Italy’s Giant Mussels

•Giant Clam

•Geoduck Clams

Byssal Threads

Class GastropodaClass Gastropoda

Class GastropodaClass Gastropoda– Largest class of molluscs, about 75,000 speciesLargest class of molluscs, about 75,000 species

– Name means "belly-footed”Name means "belly-footed”

– Coiled shell on most speciesCoiled shell on most species

– No shell on sea slugs (nudibranchs)No shell on sea slugs (nudibranchs)

– Radula for grazing on plants in most, some are Radula for grazing on plants in most, some are deposit feeders deposit feeders

– Some species are carnivorous and use radula Some species are carnivorous and use radula for prey capture (some will even prey on for prey capture (some will even prey on members of the same species)members of the same species)• Cone snailCone snail

Berkley.edu

A few Bahamian molluscsA few Bahamian molluscs

A few Bahamian molluscsA few Bahamian molluscsTide Pool Gastropods

Coral ReefFlamingo Tongue

Class CephalopodaClass Cephalopoda– Squid, octopus, nautilus, & cuttlefishSquid, octopus, nautilus, & cuttlefish

– All 650 species marineAll 650 species marine

– Fast swimming predators due to water jet Fast swimming predators due to water jet propulsionpropulsion

– Well developed eyesWell developed eyes

– Thick mantle covers the bodyThick mantle covers the body

– Use beak-like jaws and radula to crush or rip Use beak-like jaws and radula to crush or rip preyprey

– Adapted tentaclesAdapted tentacles

Class CephalopodaClass CephalopodaOctopusesOctopuses

– Shell internal or absent in most Shell internal or absent in most – Most advanced invertebrates (smart octopus)Most advanced invertebrates (smart octopus)– In octopus, the shell has been replaced by a In octopus, the shell has been replaced by a

beak-like jaw which can deliver a powerful bitebeak-like jaw which can deliver a powerful bite– Some octopus have toxic bitesSome octopus have toxic bites– Ink sac is also seen in octopus to allow escape Ink sac is also seen in octopus to allow escape

from predatorsfrom predators– A stiff internal A stiff internal ““penpen”” is seen in squid is a is seen in squid is a

modified shell; cuttlebone in cuttlefishmodified shell; cuttlebone in cuttlefish

Class CephalopodaClass Cephalopoda

Class CephalopodaClass CephalopodaSquid and CuttlefishSquid and Cuttlefish

Class CephalopodaClass Cephalopoda

• How smart is an octopus?How smart is an octopus?