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Zoology > Chapter 16: Mollusca > Flashcards

Chapter 16: Mollusca Flashcards

1
Q

Phylum Mollusca

A

Latin - molluscus (soft)
-coelomate
-extremely diveresed, 90,000 living species
-very important to humans via food and industries

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2
Q

Mollusca Characteristics

A

-dorsal body wall forms pair of folds called mantle, modified to form gills/lungs, secretes shell, ventral body wall sometimes a foot
- radula in mouth
occasionally parasitic
-bilaterally symmetrical and unsegmented, triploblastic
-circular, diagonal, and longitudinal muscles
- nervous system with many large ganglia, sometimes a well developed brain

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3
Q

mollusc characteristics pt 2

A

-hihgly developed sense organs, cephalopods have highly developed direct eye
-alway sexual reproduction
- both monoecious and dioecious forms, spiral cleavage, ancestral larvae called trochophore
-one or two kidneys called metanephridia
-gaseous exchange by gills, lungs, mantle, or body wall
-open circulatory system (closed in cephalopods)

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4
Q

mollusc form and function

A
  • always contains a head/foot and visceral mass
  • most possess a radula, a rasping, a protrusible, tongue like organ
    (as many as 250,000 teeth and new rows of tissue are continually replaced)
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5
Q

molluscan foot

A

usually for locomotion or attachment
-slimy sliding surface for snails/slugs
-muscular protuberance of bivalves
-attachment disc of limpets
-siphon of cephalopods

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6
Q

mantle and associated structure

A

mantle cavity house respiratory organs, surface functions in gas exchange

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7
Q

ctendia

A

function as countercurrent exchanger of oxygen and carbon dioxide between circulatory sytem and water or air (gills)

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8
Q

shell

A

secreted and lined by the mantle
three layers: peristracum, prismatic layer, and nacreous layer

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9
Q

peristracum

A

outer organic layer

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10
Q

prismatic layer

A

middle layer of calcium carbonate embedded in a protein matrix

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11
Q

nacreous layer

A

inner layer contrinously secreted by mantle thicken though life

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12
Q

open circuatory system

A

blood bathes the organs directly
- no distinction between blood and interstitial fluid

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13
Q

hemolyph

A

general body fluid

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14
Q

OCS path

A

contractions of 1 or more hearts pumps hemolymph through circulatory vessels into interconnected sinuses

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15
Q

closed circulatory system

A

blood confined to vessels and is distinct from the interstitual fluid
-more efficient at transporting

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16
Q

CCS path

A

materials exchanged between smallest vessels and interstitual fluids bathing cells and between interstitial fluid cells

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17
Q

digestive and nervous systems

A

digestive system complexed and highly specialized
- usually two kidneys called metanephridia where the inner opens into coelom at a nephrostome. soemtimes function to release gametes

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18
Q

mollusc reproduction

A

Trochophore larvae very similar to annelids (sometimes in an egg)
- direct metamorphisis
-some have a unique veliger larvae stage
-cephalopods have direct development

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19
Q

oyster life cycle

A

foating fertilized egg
swimming straight hinged veliger
swimming late veliger
swimming and crawling pediveliger
spat setting and attaching to oyster shells
1-3 years male and females

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20
Q

giant floater mussel

A

male releases spem and female releases mature larvae
mature larvae encyst onto fins of fish host
metamorphosing juvenile
crawling juveniles

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21
Q

zebra mussel

A
  • native to black and caspian seas, discovered in US in 1988
    -cause an estimated 40 billion dollar economic impact every year in the US
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22
Q

Classes of Phyllum Mollusca

A

Caudofoveata
Solenogastres
Polyplacophora
Monyplacophora
Gastropoda
Cephalopoda
Bivalvia
scaphopoda

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23
Q

Class Caudofoveata

A

120 species marine, wormlike burrowing animals
-feed on microorganisms and detritus
-posses an oral shell and radula
-dioecious

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24
Q

Class solenogastres

A

250 species, like caudofoveates
-no radula and no gills
-foot is pedal groove
-hermaphroditic
-feed on cnidarians

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25
Q

hermaphroditic

A

having both male and female reproductive organs,
can reproduce sexually

26
Q

Class polyplacophora

A

Chitons
-seven or eight articulated plates
-sensory organs reduced, possess esthestes
live on rocky surfaces
- clings with broad foot, can roll like armadillo,
gills along foot
3 chambered heart
- scrape algae, few preds
- have pairs of osphradia
- sexes separate, trocophores become juveniles, no veligers

27
Q

Esthestes

A

tiny ‘eyes’

28
Q

Osphradia

A

chemoreceptive sense
organs for sampling water

29
Q

Monoplacophora

A

25 species, low rounded single shell
-resemble limpets but have repeated organs (evidence of serial metamerism)
-sister group to polyplacophora

30
Q

Gastropoda

A

Most diverse, 70,000 species
- snails, slugs, limpets, conchs
- shells are chief defence, called a valve

31
Q

shells

A

starts at the apex, forms whorls downwards around a central axis called a columnella
- dextra or sinistral
- many have an operculum or cover that protects the shells opening (aperture)

32
Q

gastropod form and function

A

exhibit torsion (body can morph and twist)
ontogenetic (changes with age)

33
Q

torsion function

A

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
2 step process
- foot retraactor muscle contracts and pulls the shell and enclosed viscera (containing organs) 90 degrees counterclockwise
- brings anus from posterior to right side

34
Q

coiling

A

early gastropods planospiral (all whorls in same plane)
Conispiral shells evolved years later

35
Q

gastropod defense

A

protected shells, distasteful or toxic secretion
-some eat cnidarians and use their nematocysts for defense
-cone shells use a modified radula as a needle to inject toxin (can be fatal)
-some use foot and operculum as a weapon

36
Q

Gastropod feeding

A

Very diverse, but all use radula
Most are herbivorous

37
Q

gatropod internal form and function

A

Respiration by ctenidia
Pulmonates lack ctenidia, but have a lung, opens in a pneumostome
Usually have a single kidney
Eyes (some with a cornea and lens), photoreceptors, statocysts, tactile organs, and chemoreceptors (one called and osphradium)

38
Q

gastropod reproduction

A

Both dioecious and monoecious
Some pulmonates shoot a dart into their partner’s body to stimulate excitement!
Some marine forms enclose their eggs, some brood their eggs, some attached, some drift as plankton

39
Q

Gastropod taxonomy

A

prosobranchia
opithobranchia
pulmonata

40
Q

prosobranchia

A

marine snails, few freshwater and terrestial
- mantle cavity anterior, gills in front of heart, operculum present
(water goes up and out holes to prevent fouling)
-one pair of tentacles
-sexes separate

41
Q

opithobranchia

A

sea slugs, hares, butterflies, bubble shells
-partial or complete detorsion
-two pairs of tentacles
(second modified into rhinophores)
-shell reduced or absent
-all monoecious
-sea butterflies use foot for swimming
-some feed on cnidarians, keep nematocysts, hold them in papillae called cerata
-some sea slugs pierce algae cell eating contents

42
Q

pulmonates

A

land and freshwater snails, slugs
-lost ctenidia, vascularized mantle is lung
-anus and nephrdiopore open near pneumatostome
-some detorsion
-monecious
-aquatic forms with one pair of tentacles terrestrail forms with two,
posterior has eyes

43
Q

Class cephalopoda

A

From the Greek roots kephale (head) and podos (foot)
Squid, octopus, nautilus, devilfish, cuttlefish
All active predators
Modified foot concentrated in head region
-Takes the form of a funnel for jet propulsion
Smallest: 2 cm Largest: 18 m (60 feet)!
All marine, sensitive to salinity (like it high)

44
Q

Shell form and function

A

Nautilus have a shell with open spaces called gas chambers, enables them to have neutral buoyancy, divided by tansverse septa
- Chambers connected by cord of living tissue called a siphuncle
Cuttlefish have a small, curved shell
Squid have a nearly absent shell
Octopus have no shell

45
Q

cephalopod locomotion

A

Forcefully expel water from the siphon
-Mobile for directional control
Squid very fast, cuttlefish slower, nautilus even slower, octopus usually crawl

46
Q

cephalopod respiration

A

Nautiloids one pair of gills, all others two
- No cilia on gills, require more oxygen than cilia can get
One way valves and strong circular muscles keep water going one way
Entire systemic circuit before blood reaches gills
- Opposite of vertebrates (blood leaves heart and goes to lungs/gills)
- Have branchial hearts at base of gills to increase blood pressure

47
Q

cephalopod nervous and senosry system

A

Very elaborate systems
- Squid have the largest known nerve fibers
Eyes have statocysts, so slit shaped pupils always horizontal, regardless of the animal’s orientation
Most colorblind, but excellent visual acuity
Many trainable and good at observational learning
-Respond to positive and negative reinforcement

48
Q

cephalopod communication

A

Visual signals extremely important
-Body motions
-Color changes through chromatophores
Use ink gland for defense

49
Q

cephalopod reproduction

A

Sexes separate
One arm of adult males modified into a hectocotylus
- Plucks the spermatophore (sperm packet) and insert it into the mantle cavity of the female near the oviduct

50
Q

cephalopod taxonomy

A

nautiloidea
ammonidiea
coeloidea

51
Q

nautiloidea

A

one pair of gills
only one surviving genus with 5 species

52
Q

ammonoidea

A

all extinct in the cretaceous
-before asteroid
chambered shells with more developed septa

53
Q

coeloidea

A

squids
octopuses
cuttlefish

54
Q

Bilvalvia (Pelycopoda)

A

“Hatchet footed” animals
Mussels, clams, scallops, oysters, shipworms
Most are sedentary filter feeders
Most marine, plenty freshwater
Very important to humans

55
Q

Bivalve shell form and function

A

Two shells held together by hinge ligament
Umbo: oldest part of shell, growth emanates from it
Pearls form when foreign object lodges between mantle and shell

56
Q

bivalve Body, mantle,

A

Visceral mass suspended from dorsal midline, ctenidia hang on each side of foot
Some clams have a mantle modified into long siphons

57
Q

bivalve locomotion

A

Most push foot between valves, muscles contract for movement, extra blood increases size to be an anchor into substrate
Scallops and file shells swim by pushing water out of the mantle edges forcefully

58
Q

bivalve Gills

A

Gas exchange occurs in both mantle and gills
Some have modified these gills through lengthening of filaments, can interlock to form lamellae

59
Q

bivalve feeding

A

Most bivalves filter feeders
- Respiration brings both food and gas exchange
One group, the shipworms or “termites of the sea” bore into and eat wood
- Very damaging

60
Q

bivalve internal structures

A

Floor of most folded into ciliary tracts
- Particles sorted, nonfood excreted, food directed to digestive gland or engulfed by amebocytes
Style sac has a crystalline style and whirls by ciliary action, keeps digestive processes moving
Three chambered heart
Two U-shaped kidneys
Three pairs of ganglia separate from each other
Sense organs poorly developed
-Some have decent eyes

61
Q

bivalve reproduction

A

Sexes usually separate, gametes usually discharged into water
Glochidium: specialized veliger
Some females hold glochidia in a specialized pouch called a conglutinate, specific shape for each species

62
Q

Scaphopoda

A

Tusk shells or tooth shells,
one piece tubular shell, conical at both ends
No gills
Have long feeding tentacles with ciliated knobs called captacula
Radula carries food to a gizzard
No eyes, sensory tentacles, or osphradia
Sexes separate, trochophore larvae

Zoology (3 decks)

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