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Molluscs Flashcards

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1
Q

What makes blue-ringed octopus dangerous?

A

Tetrodotoxin causes paralysis while the victim remains conscious.

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2
Q

Name the largest known invertebrate.

A

Colossal squid (Mesonychoteuthis hamiltoni), up to 30 m.

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3
Q

How old is the cephalopod fossil record?

A

Dates back to the Ordovician (~480 million years ago).

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4
Q

What is an octopus midden?

A

A pile of discarded prey remains outside its den—evidence of feeding and tool use.

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5
Q

What is notable about squid axons?

A

They have giant axons used for rapid escape responses.

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6
Q

Name some notable cephalopod behaviours.

A

Camouflage, mimicry (e.g., Sargassum posture), deimatic displays (eyespots), “bad hair” defence posture.

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7
Q

What is the hectocotylus?

A

A modified arm in males for sperm transfer, often breaks off during mating.

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8
Q

How do octopus eggs develop?

A

Direct development—no larval stage.

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9
Q

What is the term for cephalopods reproducing once and dying?

A

Semelparity.

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10
Q

How is the squid shell modified?

A

It is internal and vestigial—called a “pen.”

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11
Q

What is the shell structure of cuttlefish called?

A

Cuttlebone—internal, spongy, helps with buoyancy.

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12
Q

What does the siphuncle do in nautilus?

A

Regulates gas and fluid in shell chambers for buoyancy.

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13
Q

What is unique about nautilus reproduction?

A

They reproduce many times (iteroparous), unlike other cephalopods.

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14
Q

What is the function of the ink sac?

A

Defense—creates a visual/sensory smokescreen.

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15
Q

How do cephalopods move?

A

Jet propulsion via the siphon, walking, or fin movement.

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16
Q

How many arms/tentacles do octopuses and squids have?

A

Octopuses: 8 arms. Squid/Cuttlefish: 8 arms + 2 tentacles.

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17
Q

What distinguishes arms from tentacles?

A

Arms have suckers along their length; tentacles only have suckers at the tip

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18
Q

Which cephalopod is considered a “living fossil”?

A

Nautilus.

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19
Q

Name the main orders of Cephalopoda.

A

Nautilida, Teuthida, Sepiida, Sepiolida, Octopodida, Ammonoida (extinct), Spirulida.

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20
Q

What is unique about cephalopod vision?

A

They have vertebrate-like eyes, can detect polarised light, and may see in colour.

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21
Q

What is a statocyst?

A

A sensory organ for balance and low-frequency sound detection.

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22
Q

What are photophores and what do they do?

A

Light-producing organs, used for signaling, camouflage, prey attraction

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23
Q

What are chromatophores used for?

A

Camouflage, defense, communication.

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24
Q

What makes cephalopod brains special among invertebrates?

A

They are highly developed, allowing complex learning and behaviour.

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25
What part of the body do arms and tentacles derive from in cephalopods?
From the mantle
26
What structure evolved from the posterior foot in cephalopods?
Funnel (siphon).
27
What type of circulatory system do cephalopods have?
Closed circulatory system with 3 hearts.
28
What are key features of all cephalopods?
Mobile, large head, large brain, large image-forming eyes, predators, jet propulsion, high metabolic rate.
29
What is the "love dart"?
A calcareous spicule injected during mating to stimulate reproduction in pulmonates.
30
What do names of mollusc classes indicate?
Often relate to shell structure or body shape: e.g., Polyplacophora = many plates; Scaphopoda = shovel foot
31
What class of molluscs is the largest?
Gastropoda (~70,000 described species, ~15,000 fossil species)
32
What do cone snails use to catch prey?
Venomous harpoon-like radula loaded with neurotoxins tailored to prey type
33
Which gastropods are pelagic?
Pteropods (sea butterflies), Janthina (bubble raft snails)
34
How do pulmonates reduce water loss?
Secrete mucus, have a lung-like cavity, close shell aperture with mucus, respiratory and genital pores
35
What are Aplysia used for in science?
Studies on neurophysiology and learning due to their simple nervous system
36
What are key reproductive traits of pulmonates?
Hermaphroditic, use of love darts, simultaneous mutual copulation, long penes, sperm storage
37
What is the function of mucus nets in feeding?
Used by some pelagic and sessile gastropods to trap plankton and suspended particles
38
What are cerata in opisthobranchs?
External gill structures that may also house defensive nematocysts or toxins
39
What is the difference between dextral and sinistral coiling?
Dextral: aperture on right when apex pointed away. Sinistral: aperture on left
40
What adaptations help deal with waste near the head due to torsion?
Shell slits, water flushing, Bernoulli effect, separation of inhalant and exhalant flows
41
What is the osphradium?
A chemosensory organ near the gills that samples water for chemical signals
42
What is the function of the operculum in gastropods?
A horny or calcareous plate that seals the shell opening when the animal retracts, preventing desiccation or predation
43
How do gastropods feed?
Use radula to scrape, graze, or drill; some use mucus nets or toxins (e.g., cone snails)
44
What defines Pulmonata?
Mantle cavity acts as lung, terrestrial/freshwater, reduced or no operculum, secretes mucus, hermaphroditic
45
What defines Opisthobranchia?
Lateral/posterior gills (cerata), often lack shells, detorted, often chemically defended, marine
46
What defines Prosobranchia?
Anterior gills, mostly marine, may have operculum, includes diverse feeding types (grazers, predators, parasites)
47
Example animals for Pulmonata?
Land slugs and snails, some freshwater and marine forms
48
Example animals for Opisthobranchia?
Sea slugs, nudibranchs, sea hares, pteropods
49
Example animals for Prosobranchia?
Whelks, cone shells, limpets, abalone
50
What are the three major subclasses of Gastropoda?
Prosobranchia, Opisthobranchia, Pulmonata
51
What are the consequences of torsion?
Anus near head, potential sanitation issues, organs twisted, allows head to retract into shell first, may increase protection.
52
What is torsion in gastropods?
A 180° anticlockwise twisting of the visceral mass during larval development, resulting in the anus near the head.
53
What are key features of gastropods?
Coiled shell, torsion (90°-180°), operculum, well-developed head with tentacles and eyes, creeping foot movement via peristaltic muscle contractions.
54
What is the purpose of siphons in bivalves?
To draw in and expel water while remaining buried for protection.
55
What kind of symbiosis can bivalves have?
With Symbiodinium (giant clams) or sulfur-oxidizing bacteria
56
Which bivalves can swim?
Scallops
57
What are common bivalve lifestyles?
Sessile, burrowing, swimming, boring.
58
What is the function of the bivalve foot?
Burrowing and testing the environment (contains blood sinus).
59
What is sclerochronology?
The study of shell growth patterns to reconstruct past environmental conditions.
60
What bivalves are in Eulamellibranchia?
Clams, cockles, freshwater mussels; advanced filter feeders with fused gills.
61
What bivalves belong to Lamellibranchia?
Mussels, oysters, scallops; filter feeders with filibranch gills.
62
Give an example and features of Protobranchia.
Nucula species; marine, deposit feeders, gills for respiration only.
63
What are the three major subclasses of Bivalvia?
Protobranchia, Lamellibranchia, Eulamellibranchia.
64
What is the key trait of Protobranchia?
Gills for gas exchange only; deposit feeders (e.g., Nucula).
65
What is the crystalline style?
A rod in the gut that rotates to aid in grinding food and enzyme release.
66
What structure sorts food particles in mussels?
Labial palps (chemosensory).
67
What are eulamellibranch gills?
Fused filaments forming ostia, creating a sieve for efficient feeding using Bernoulli's principle.
68
What are filibranch gills?
Ciliated filaments that beat water through the gill.
69
What feeding structure evolved in Lamellibranchs?
Leaf-like gills adapted for filter feeding.
70
How are protobranch gills used?
Gas exchange only; not used for feeding.
71
What is the umbo?
The oldest part of the shell, used to determine the natal environment.
72
Why is shell chemistry important in ecology?
Used in larval connectivity studies and environmental reconstructions (e.g., Schlerochronology).
73
What is the periostracum made of?
Conchin – a protein.
74
What are the three main shell layers in bivalves?
Periostracum (protein), Prismatic (calcite), and Nacreous (aragonite).
75
What secretes the bivalve shell?
The mantle.
76
What feeding strategies are common in bivalves?
Mostly suspension or deposit feeding.
77
What is the function of adductor muscles in bivalves?
Shell closure; relaxed = open, contracted = closed.
78
How is the bivalve body oriented?
Laterally flattened and enclosed within the shell.
79
Do bivalves have a head or radula?
No, they lack both a head and a radula.
80
What is the main feature that gives bivalves their name?
A shell composed of two valves.
81
Which molluscs have two shells?
Bivalvia (e.g. clams, mussels, oysters).
82
Which molluscs have no shell?
Aplacophora and some gastropods (e.g. slugs, nudibranchs).
83
What is the mantle’s function?
Secretes shell, forms siphons, encloses gills, aids in respiration, camouflage.
84
What does the mollusc foot do?
Locomotion, digging, tentacle/arm formation (in cephalopods), crawling, or swimming.
85
How is the mollusc nervous system structured?
Ganglia connected by nerve cords; cephalopods have advanced brains and eyes.
86
Ganglia connected by nerve cords; cephalopods have advanced brains and eyes.
Mostly dioecious, some hermaphrodites, external/internal fertilization, trocophore and veliger larvae.
87
What type of circulatory system do most molluscs have?
Open circulation; cephalopods have a closed system.
88
What is the crystalline style?
A rotating rod in the gut that grinds food trapped in mucus and aids digestion.
89
What is a radula?
A chitinous tongue-like organ with rows of teeth used for scraping, drilling, or injecting venom.
90
What are the three major feeding strategies in molluscs?
Herbivory (grazing, suspension, deposit), predation (pelagic, benthic), and parasitism.
91
Why is mollusc shell formation sensitive to climate change?
Ocean acidification lowers pH, affecting calcium carbonate availability for shell formation.
92
What is the shell of a mollusc made of?
Calcium carbonate in a protein matrix; layers include periostracum (conchin), prismatic (calcite), and nacreous (aragonite).
93
What societal roles do molluscs play?
Aquaculture, fisheries, food, materials, jewellery, regenerative aquaculture.
94
What is bentho-pelagic coupling?
Molluscs filter particles from water and excrete nutrients, enhancing productivity for primary producers.
95
How do molluscs function as habitat engineers?
Build reefs, provide substrates, and bioturbate sediments.
96
Why are molluscs important in ecosystems?
They are abundant grazers, predators, prey, habitat engineers, and play roles in nutrient cycling.
97
What larval stage is unique to molluscs?
Veliger larva.
98
What are the key features unique to molluscs?
Shell, muscular foot, mantle, crystalline style, radula, veliger larvae.
99
Name seven classes of Mollusca.
Monoplacophora, Aplacophora, Polyplacophora, Scaphopoda, Gastropoda, Bivalvia, Cephalopoda.
100
What are the general characteristics of molluscs?
Bilateral, unsegmented, coelomate, protostome, metazoans.

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