Zoology ch 16 Molluscs

what does the latin root molluscus mean?

soft

how many living species of organisms are in phylum molluscus?

90,000

t/f moolluscs have a good fossil record

true, very extensive and detailed fossil record

what are molluscs used in? why are they important to humans?

food, industrial processes

what is the Kraken?

mythological creature in Norse mythology

what type of muscles do mollusc posses?

circular, longitudinal, diagonal

molluscs have a nervous system with many large ___

ganglia, sometimes a well developed brain

t/f molluscs are bilaterally symmetrical and unsegmented

true

are molluscs triploblastic or diploblastic

triploblastic

where is the radula located?

in mouth

molluscs general description

Dorsal body wall forms pair of folds called mantle, modified to form gills or lungs, secretes shell, ventral body wall sometimes a foot

t/f molluscs have highly developed sense organs

true, cephalopods have highly developed direct eye

what type of reproduction do molluscs always exhibit

sexual

what type of forms do molluscs have?

both monoecious and diecious

what is the ancestral larvae called?

trochophore

what type of cleavage do molluscs have?

spiral cleavage

what is the kidney of mollusc called?

metanephridia

how do molluscs exchange gases?

by gills, lungs, mantle, or body wall

what kind of circulatory system do molluscs have?

open circulatory system

what kind of circulatory system do cephalopods have?

closed circulatory system

what do molluscs always contain?

head/foot and a visceral mass

what is a radula?

a rasping, protrusible tonguelike organ used for feeding
- As many as 250,000 teeth

• most gastropoda are herbivores

what is the foot used for in molluscs?

Usually for locomotion or attachment

t/f the foot of molluscs is not very diverse

false, very very diverse

what is the foot used for in snails/slugs?

Slimy sliding surface

what is the foot used for in bivalves?

Muscular protuberance

what is the foot used for in limpets?

Attachment disc

what is the foot used for in cephalopods?

siphon

what does the mantle cavity house?

respiratory organs, surface functions in gas exchange

what is the function of the Ctenidia (goose foot example in class)

countercurrent exchanger of oxygen and carbon dioxide between circulatory system and water or air

t/f many taxa can’t withdraw their head into the mantle cavity

false, they can

how many layers are in the shell?

3

what lines and secretes the shell?

the mantle

Periostracum

outer, rough, proteinaceous layer; very tough

Prismatic layer

middle layer of calcium carbonate embedded in a protein matrix

Nacreous layer

inner layer continuously secreted by mantle, thickens through life

what is an Open circulatory system

blood bathes the organs directly

where is an open circulatory system found?

Insects, arthropods, most molluscs

t/f there is no distinction between blood and interstitial fluid

true, General body fluid called hemolymph

what animals is the closed circulatory system found in?

Annelids, cephalopods, all vertebrates

what is the closed circulatory system?

Blood confined to vessels & is distinct from the interstitial fluid

what is a closed system more efficient at doing?

transporting circulatory fluids to tissues & cells

how many hearts are in a closed circulatory system?

One/more hearts pump blood into large vessels that branch into smaller ones, coursing through organs

t/f the digestive system is simple in molluscs

false, complex and highly specialized, lots of dietary diversity

what is the opening of the kidney?

nephrostome

what does the kidney duct sometimes function as?

release gametes

t/f the Nervous system usually more complex than annelids or arthropods

false, more simpler

cephalopods have a large developed…

brain, very large optical lobe

what is a veliger?

unique larval stage that can also exhibit torsion

direct metamorphosis is what for mollusca?

ancestral

what do cephalopods exhibit?

direct development

when were zebra mussels first discovered in the US?

1988

where are zebra mussel native to?

Black and Caspian Seas

how were zebra mussels introduced to America?

via ballast water

how much is the estimated economic impact?

40 billion dollars

how many species of Class Caudofoveata are there?

About 120 species of marine, wormlike, burrowing animals

what do Caudofoveata feed on?

microorganisms and detritus

are Caudofoveata monoecious or dioecious?

Dioecious

what do Caudofoveata possess?

oral shield and a radula

how many species are in the class Solenogastres?

about 250

what do Solenogastres possess?

No radula and no gills, foot is a pedal groove

what do Solenogastres usually feed on?

Cnidarians

how long did it take for zebra mussels to evolve heat resistance?

10 years

what does the greek root Chiton mean?

coat of mail, tunic

what are Polyplacophora commonly known as?

sea beef

how many articulated plates does Polyplacophora have?

7-8 plates

what photosensitive structure do Polyplacophora possess?

esthestes

where do Polyplacophora live?

rocky surfaces in intertidal regions

what kind of heart do Polyplacophora have?

3 chambered heart

Polyplacophora have a pair of…?

osphradia

what is the function of osphradia?

chemoreception in mantle cavity

t/f the sexes are separate in Polyplacophora

true, trochophores become juveniles, no veliger stage

How many species are in Class Monoplacophora

about 25

what are monoplacophora the sister group to?

Polyplacophora

what is serially repeated in Monoplacophora?

organs, evidence of serial metamerism

How many species are in the class gastropoda?

70,000 species (most diverse of molluscs)

what is the main defense of Gastropoda

shells, called a valve, always univalve

what is the central axis of the shell

columnella

what is more common in snails, sinistral or dextral?

dextral (right handed), genetically controlled

what is the cover that protects the shell’s opening

operculum

what is the shell’s opening called?

aperture

what is torsion?

all of the body morphs and changes through twisting

when does torsion happen

during or after the veliger stage

• ontogenetic - changes with age

how many steps is the veliger torsion process?

2 step

how does the digestive tract move during torsion?

laterally and dorsally

in what direction does the foot retractor muscle contract and pull the shell and viscera?

90 degrees counterclockwise

what is the function of torsion?

• Puts gills and mantle cavity up front

• Allows foot to be pulled in last for protection

• Puts anus and mouth on same side, outside shell

what does detorsion occur in?

opistobranchs and pulmonates

what is torsion derived from?

torted ancestors

what problem does torsion create?

Anus opens over head and gills (fouling)

• waste being washed over respiratory structures

why does torsion happen?

Deals with coiling and the original/final placement of organs

what have some modern gastropods evolved?

planospirality

t/f conispiral shells evolve before planospiral

false, evolve later, early gastropods were planospiral

did coiling originate before or after torsion?

before torsion (torsion evolves later to deal with this)

what are other forms of gastropod defense?

shells, distasteful or toxic secretions

why do some gastropods eat Cnidarians?

incorporate nematocysts, use them for defense

what do cone shells use as protection?

modified radula as a needle to inject toxin

what do fighting conchs use as a weapon? (video in class)

foot and operculum

what do gastropods use for respiration?

ctenidia, two is the ancestral condition

what do pulmonates lack?

ctenidia