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BIOL 321 > Phylum Mollusca > Flashcards

Phylum Mollusca Flashcards

1
Q

the shell of molluscs is made of:

A

calcium carbonate

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2
Q

defining characteristics of molluscs (3)

A
  1. dorsal epithelium forms mantle
  2. radula (except bivalves)
  3. ventral body wall muscles develop into foot
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3
Q

chitons (class)

A

Class Polyplacophora

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4
Q

chitons have how many osphradia?

A

two

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5
Q

defining characteristics of chitons (5)

A
  1. minimal cephalization
  2. dorso-ventral flattening
  3. 8 shell plates
  4. thickened mantle - ‘girdle’
  5. radula with magnetite-capped teeth
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6
Q

significance of the 8 shell plates

A

bodies can conform to uneven topography

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7
Q

how does the mantle of chitons assist with substrate adhesion?

A

press with the periphery of mantle and raise interior of mantle cavity to create negative pressure for suction

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8
Q

what is the function of magnetite caps on teeth

A

hardening of radular teeth

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9
Q

where are the two osphradia of chitons located

A

either side of the anus

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10
Q

differences between coelomic compartments in annelids vs. molluscs

A

molluscan compartments are much smaller
dorsal blood vessel is more muscular- forms ‘heart’
ultrafiltration into the perciardium
connection between gonads and pericardium lost in molluscs

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11
Q

radula of molluscs are inside of the:

A

buccal mass

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12
Q

teeth of radula are secreted by the:

A

radular sac

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13
Q

____ are the only molluscs lacking radula

A

bivalves

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14
Q

chiton reproduction

A

dioecious
broadcast spawn gametes
external fertilization

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15
Q

larva of chitons is similar to

A

trochophore larva (ciliated and non-feeding)

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16
Q

chitons have which type of ctenidia

A

bipectinate

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17
Q

blood flow is ____to the direction of water flow in chitons

A

opposite - countercurrent exchange

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18
Q

monoplachophora is sister to all other____

A

conchiferans

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19
Q

monoplachophorans have __ pairs of metanephridia and __ pairs of gonads

A

2; 2

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20
Q

which is the largest class of molluscs?

A

gastropoda

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21
Q

2 major defining characteristics of gastropods

A
  1. torsion

2. operculum

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22
Q

2 major body regions of gastropods

A

cephalopodium and visceropallium

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23
Q

the shell of gastropods evolved as:

A

a protective retreat for the head and foot

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24
Q

what is the columella in gastropods

A

the central column of calcium carbonate that the shell coils around

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25
Q

the ancestor of all gastropods was likely ___-like

A

monoplacophoran

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26
Q

the contraction of which muscles draws the head and foot into the gastropod shell

A

columellar muscles - extend from the foot to the central axis

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27
Q

function of the operculum in gastropods

A

drawn in last (following the head and foot) and seals the operculum of the shell

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28
Q

according to the torsion hypothesis, what happens between the monoplacophoran state and intermediate state?

A

reduction of:

  • shell aperture
  • # of shell muscles
  • # of ctenidia
  • posterior mantle cavity
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29
Q

according to the torsion hypothesis, what happens between the intermediate state and gastropod state?

A

180 degree rotation of the visceropallium relative to the cephalopodium

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30
Q

evidence for torsion (2)

A
  1. anatomy of living gastropods - crossover of visceropallial nerve cords
  2. development of basal gastropods - rotation during development
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31
Q

adaptive value of torsion in larval stages

A

survival adaptation - carried into the adult stage

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32
Q

adaptive value of torsion in adult stages

A

ctenidia and osphradia become located at the front, in the direction of locomotion

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33
Q

what is the fouling problem in gastropods

A

the anus discharges over the head - inefficient turbulence and circulation of water in the mantle cavity might have fecal material

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34
Q

solutions to the fouling problem (2)

A
  1. shell perforations : one way water flow lessens contamination (vetigastropoda)
  2. shift of the anus to the right side (caenogastropoda)
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35
Q

all vetigastropods have shell perforations and __ ctenidia

A

two

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36
Q

caenogastropods lose the ____ ctenidia as the anus shifted to the right side

A

right

37
Q

what is the primitive feeding strategy of gastropods

A

herbivorous grazing using radula

38
Q

feeding strategies of caenogastropods (2)

A
  1. herbivorous grazers

2. predators - use proboscis

39
Q

what makes predatory gastropods unique?

A
  • expanded body wall around the mouth
  • body wall opens into proboscis sac
  • elongation of anterior esophagus
40
Q

what makes shell drills unique?

A
  • accessory boring organ at the tip of the proboscis
  • likely secrete toxins
  • mucus and sand used to produce egg case
41
Q

elaboration of mid-esophageal gland in moon snail

A

elaborated into venom gland that excretes conotoxins

42
Q

what is unique about the proboscis of moon snails?

A

no radular ribbon of teeth - hollow harpoon at the end of the proboscis instead

43
Q

what are conotoxins?

A

small peptides that target neural antigens

44
Q

defense strategies of marine heterobranchs (4)

A
  1. chemical defense - toxic secondary metabolites taken from prey or secreted by themselves
  2. escape/defensive behaviour - flexions takes them to prevailing current to carry them
  3. sequestration of cnidocytes - store nematocysts from cnidarians in cnidosacs
  4. autotomy - cell cutting of cerata along autotomy plane
45
Q

adaptations of terrestrial heterobranchs (3)

A
  1. mantle cavity forms internalized ‘lung’ with pneumostome to exterior
  2. conversion of ammonia to uric acid to preserve water
  3. aestivation - metabolic slow-down, tolerate dessication and rapidly rehydrate
46
Q

reproduction strategy in vetigastropods

A

broadcast spawning - external fertilization

47
Q

reproduction strategy in caenogastropods and heterobranchs

A

internal fertilization and encapsulated eggs

48
Q

gastropod larval type

A

veliger larvae

49
Q

major characteristics of class bivalvia (5)

A
  1. laterally compressed
  2. 2 lateral shell valves hinged dorsally
  3. spacious lateral mantle cavities - each with ctenidium
  4. minimal cephalization
  5. no radula
50
Q

what is the foot used for in bivalves

A

burrowing

51
Q

adductor muscles in bivalves are used to:

A

close the shell

52
Q

how do bivalves burrow

A

contraction of circular muscles projects the foot into the substrate, the foot then expands to form terminal anchor

53
Q

what is the periostracum of bivalves?

A

layer of protein secreted by between middle and outer lobes - covers the calcium carbonate shell

54
Q

where do the pallial muscles of bivalves insert?

A

run from the inner lobe to the point where the mantle touches the shell

55
Q

what are the pallial muscles used for?

A

pull the periphery of the mantle fold into the shell so it can be closed tightly without tissue caught inside

56
Q

3 lobes of bivalves and their function

A
  1. inner lobe - muscular
  2. middle lobe - sensory
  3. outer lobe - secretes periostracum
57
Q

what is the function of hinge teeth

A

interlock to prevent shell valves from laterally slipping

58
Q

how do protobranchs feed

A

deposit feeding using palp tentacles

59
Q

the ctenidia of protobranchs are used for:

A

gas exchange only

60
Q

most bivalves have ______ ctenidia

A

lamellibranch

61
Q

3 types of cilia on demibranch of lamellibranch ctenidia

A
  1. lateral cilia - create water current/draw water in
  2. laterofrontal cilia - intercept flow of particles
  3. frontal cilia - carry particles to frontal apex ‘elbow’ of gill filaments
62
Q

septibranchs feeding strategy

A

predators

  • use suction via inhalant siphon to suck prey into mantle cavity
  • highly modified gill with perforations elevates and increases volume of mantle cavity to create negative pressure
63
Q

which bivalve has byssal threads and what are they used for

A

mussels - byssal threads are secreted by byssal glands for attachment to rocky substrates

64
Q

how does attachment work in mussels

A

byssal gland secretes liquid that runs down a groove in the foot and creates puddle on the substrate
- the foot is then removed and byssal strands remain to keep the mussel attached

65
Q

what allows shipworms to damage wood

A

ctenidia are populated with enzymes that break down cellulose

66
Q

defining characteristics of Class Cephalopoda (4)

A
  1. shell divided by septa - chambers connected by siphuncle
  2. closed circulatory system
  3. foot modified to form flexible arms and siphon
  4. ganglia fused to form large brain enclosed in cartilaginous cranium
67
Q

molluscan characteristics found in cephalopods (3)

A
  1. radula
  2. molluscan - style ctenidia (but not ciliated)
  3. shell secreting mantle (shell often reduced or lost)
68
Q

distinctive characteristics of Cephalopods (different from other molluscans (2))

A
  1. septate shell

2. highly modified foot

69
Q

what is the difference between a funnel and a siphon

A

funnel is derived from foot tissue

70
Q

which cephalopods show the most primitive characteristics

A

nautilus

71
Q

characteristics of nautiloidea

A
  • tentacles without suckers

- external shell that can be sealed with hood

72
Q

water flow in nautiloidea

A

water enters on either side of the head into the mantle cavity, passes over ctenidia and out through funnel

73
Q

what facilitates water flow in nautiloidea

A

muscular contractions of the funnel

74
Q

which structure is responsible for the gas filled chambers? how does this work?

A

the siphuncle - replaces fluid within cavities with gas in order to maintain neutral buoyancy

75
Q

how does the gas in the chambers of Nautilus maintain volume during diel vertical migration?

A

because of the rigidity of the shell

76
Q

why do Nautiloids undergo diel vertical migration?

A

to avoid visual predators

77
Q

what might be the reason for the adaptations found in squid?

A

competition with fish

78
Q

adaptation of shell in squids

A

reduced to proteinaceous internalized “pen”

79
Q

what is used for slow swimming in squids

A

undulation of the fins

80
Q

what is used to facilitate jet propulsion in squids

A

muscular pumping of the mantle

81
Q

how does jet propulsion work in squids?

A

radial muscles contract, expands mantle cavity and creates area of negative pressure, sucking water in on either side of the head
- circular muscles then contract, forcing the water out through the funnel

82
Q

what allows the alteration of swimming patterns in squid?

A

the ability to point the funnel in different directions

83
Q

which sensory modality is most important for squids as predators?

A

visual

84
Q

typical mollusc blood vascular system

A

oxygenated blood is passed via dorsal blood vessels

- blood percolates through hemal system connective tissue

85
Q

cephalopod blood vascular system

A
  • branchial heart increases the blood pressure before becoming oxygenated again – increases efficiency
  • blood capillaries efficiently deliver oxygenated blood to specific tissues
86
Q

what is the function of branchial hearts in cephalopods?

A

act as booster pumps to force blood through gills

87
Q

what accounts for the high metabolic rate of cephalopods (3)

A
  1. ventilation of gills by pumping of muscular mantle
  2. closed circulatory system - capillary beds
  3. systemic and branchial hearts
88
Q

what are chromatophores in cephalopods

A

pigment-filled cells, rapidly changing colours

89
Q

what happens to chromatophores when muscles contract?

A

chromatophores enlarge

BIOL 321 (5 decks)

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