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BISC 306 > Molluscs (+Brachiopods) > Flashcards

Molluscs (+Brachiopods) Flashcards

1
Q

what are the names of layers in a mollusc shell?

A

outer = periostracum (organic)
middle = prismatic (calcium carbonate without magnesium)
inner = nacreous (calcium carbonate with magnesium)

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2
Q

what is the name of the ciliated gas exchange structure used by molluscs?

A

ctenidium

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3
Q

what features make a mollusc’s gas exchange system effective?

A
  • ciliated
  • bipectinate (forked, increases SA)
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4
Q

what feeding structures do molluscs have?

A
  • radula (chitinous invagination of pharynx)
  • odontophore (sits underneath radula)
  • retractor muscles
  • protractor muscles
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5
Q

what structures do molluscs use to move around?

A
  • foot (ventral muscular extension)
  • pedal retractor muscles
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6
Q

Gastropods
what shape are gastropods’ shells?

A

single and spiraled

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7
Q

Gastropods
what is the name of the group of gastropods without a shell?

A

opisthobranchs (nudibranchs)

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8
Q

Gastropods
what common species are found in Gastropoda?

A
  • limpets (cone shaped shell)
  • snails (spiral shell)
  • opisthobranchs (nudibranchs)
  • ‘sea slugs’ (no shells)
  • sea angels
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9
Q

Gastropods
what are the three types of nudibranchs?
what characteristics define each one?

A

dorid = has gill plume on posterior end of dorsal side
dendronoid = has branched cerata (dorsal projections)
aeonid = has cerata (dorsal projections)

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10
Q

Gastropods
what are the three groups within Gastropoda?

A
  • prosobranchs (have siphons for water entry and osphiradiums) –> sea snails, limpets etc.
  • opisthobranchs (lack or have reduced shells) –> nudibranchs
  • pulmonata (have land based respiration instead of ctenidia) –> snails, slugs
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11
Q

Gastropods
what unique trait allows cone shells to be effective predators?

A

barbed radula with toxins and pheromones

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12
Q

Gastropods
describe the pathway of gastropod circulatory systems

A
  • oxygen enters blood stream via ctenidia
  • oxygenated blood goes to heart
  • heart pumps oxygenated blood into hemocoel
  • deoxygenated blood from hemocoel returns to ctenidia
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13
Q

Gastropods
what kinds of nephridia do gastropods have?

A
  • excretory
  • reproductive
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14
Q

Gastropods
what disparities do gastropods have?

A
  • well developed heads
  • torsion (twisted internal structure)
  • shell coiling
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15
Q

Gastropods
what are the axis of symmetry for gastropods?

A

anterior = mouth end
posterior = anus end

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16
Q

Gastropoda
what feeding techniqiues can a gastropod have?

A
  • grazing
  • suction
  • drilling
  • photosynthesis
  • suspension
  • toxic harpooning
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17
Q

what three classes have veliger stages after being a trochophore?

A
  • bivalvia
  • scaphophora
  • gastropoda
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18
Q

describe the veliger larva stage

A
  • has a velum (projected cilliar disc) for swimming and feeding
  • develops a mantle shell
  • can swim far distances
  • develops into adults once settling down
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19
Q

Polyplacophora
what are the common names of polyplacophores?

A

chitons

20
Q

Polyplacophora
what is unique about polyplacophore mantles?

A

made up on 8 plates versus the typical 1

21
Q

Polyplacophora
what feeding niche do polyplacophores fill?

A

grazers

22
Q

Polyplacophora
what disparities do chitons have?

A
  • reduced central nervous system
  • has hundreds of small eyes along plates
  • no tentacles
23
Q

Scaphopoda
describe the shell of a scaphopod and how it is used

A
  • long, tubular shell with an opening at the tip
  • water enters and exits through the tip
24
Q

Scaphopoda
how do scaphopods eat?

A

uses sticky bulbs on feeding tentacles at the foot pick out organic matter in sediment

25
Q

Scaphopoda
what are the axis of a tusk shell? (up/down/left/right)

A

pointing up = dorsal
pointing down = ventral
left = anterior (concave)
right = posterior (convex)

26
Q

Scaphopoda
what disparities do scaphopods have?

A
  • orientation (L/R –> anterior/posterior)
  • no ctenidia
27
Q

Bivalvia
what common species are found in Bivalvia?

A
  • scallops
  • clams
  • oysters
  • mussels
  • cockle
28
Q

what do infaunal and epifaunal mean?

A

infaunal = buried in sediment
epifaunal = live on top of benthic sediment

29
Q

Bivalvia
what disparities do bivalves have?

A
  • no head
  • no radula (filter feed instead)
  • no odontophore
30
Q

Bivalvia
what are the axis for clams and oysters?

A

left = left shell (curls to the right)
right = right shell (curls to the left)
ventral = “mouth” opening (far from hinge)
dorsal = hinge side
anterior = shorter outer edge
posterior = longer outer edge (siphon is here)

31
Q

Bivalvia
what are the axis for mussels?

A

posterior = wide end
anterior = narrow end
ventral = arched or flat end
dorsal = wide end
left = right of hinge
right = left of hinge

32
Q

Bivalvia
what are the axis for scallops?

A

left = facing up
right = facing down
anterior = larger auricle
posterior = smaller auricle
ventral = “mouth” end
dorsal = hinge end

33
Q

Bivalvia
briefly describe the path of water through a bivalve

A

water enters via incurrent siphon (ventral) and exits via excurrent siphon (dorsal)

34
Q

Bivalvia
how do bivalves feed?

A
  • food enters via mucus strings
  • labial palps filter through food and directs edible materials into mouth
  • after digestion, excretion exits the anus near the excurrent siphon
35
Q

Bivalvia
what differences in siphons do infaunal and epifaunal bivalves have?

A

infaunal (buried) = long siphons
epifaunal (above surface) = short siphons

36
Q

Bivalvia
how do bivalves open and close their shells?

A

adductor muscles relax = shell opens
adductor muscles contract = shell pulls shut

37
Q

Aplacophora
what disparities do aplacophores have?

A
  • reduced foot
  • reduced mantle (single pair of ctenidia)
  • reduced shell (no shell, has spicules)
  • reduced head (no eyes/tentacles)
  • no specialized sensory/feeding structures
38
Q

Cephalopoda
what are the axis of a squid?

A

ventral = arm end
dorsal = fin end
anterior = opposite to funnel
posterior = side with funnel

39
Q

Cephalopoda
what disparities do cephalopods have?

A
  • highly derived CNS (large brain)
  • reduced/lost shell (exception = nautilus)
  • foot has become tentacles, funnel and arms
  • closed circulatory system
  • head is ventral not anterior
  • mantle is muscular
40
Q

Cephalopoda
what do siphuncles do in a nautilus?

A

maintains buoyancy by regulating gas

41
Q

Cephalopoda
what structure helps squid and octopus hunt?

A

chitinous beak on mouth

42
Q

Cephalopoda
describe the pathway for food in a squid

A
  • mouth
  • esophagus
  • stomach
  • caecum (digestive enzymes here)
  • intestines
  • anus
43
Q

Cephalopoda
describe the pathway for blood flow in a squid

A
  • 2 branchial hearts bring deoxygenated blood to ctenidia
  • ctenidia sends oxygenated blood to systemic heart
  • systemic heart pumps blood to body and returns to branchial hearts
44
Q

Cephalopoda
how do squids pump water to ctenidia?

A

muscle contraction (versus cilia current)

45
Q

Cephalopoda
describe the pathway for sperm in a squid

A
  • produced in testis
  • passed through sperm duct (vas deferens)
  • seminal vesicle packages sperm into spermatophores (coated with cement body)
  • passed to spermatophore sac
  • hectodactyl arm pulls spermatophores out for insemination
46
Q

Cephalopoda
describe the pathway for eggs in a squid

A
  • created in ovary
  • passed through ovaduct
  • oviducal, nidamental glands package eggs into ribbons
  • fertilized eggs secreted out funnel
47
Q

Brachiopods
how do brachiopods differ from bivalves?

A
  • brachiopod = shells are dorsally/ventrically
    symmetrical
    bivalves = shells are left/right symmetrical
  • 2 sets of muscles used to control shells (abductor and adductor) vs one set of bivalves (adductor)
  • lophophore used for gas exchange vs ctenidia

BISC 306 (14 decks)

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