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Zoology > Chapter 16: Mollusca > Flashcards

Chapter 16: Mollusca Flashcards

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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
hermaphroditic
having both male and female reproductive organs, can reproduce sexually
26
Class polyplacophora
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
Esthestes
tiny 'eyes'
28
Osphradia
chemoreceptive sense organs for sampling water
29
Monoplacophora
25 species, low rounded single shell -resemble limpets but have repeated organs (evidence of serial metamerism) -sister group to polyplacophora
30
Gastropoda
Most diverse, 70,000 species - snails, slugs, limpets, conchs - shells are chief defence, called a valve
31
shells
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
gastropod form and function
exhibit torsion (body can morph and twist) ontogenetic (changes with age)
33
torsion function
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
coiling
early gastropods planospiral (all whorls in same plane) Conispiral shells evolved years later
35
gastropod defense
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
Gastropod feeding
Very diverse, but all use radula Most are herbivorous
37
gatropod internal form and function
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
gastropod reproduction
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
Gastropod taxonomy
prosobranchia opithobranchia pulmonata
40
prosobranchia
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
opithobranchia
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
pulmonates
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
Class cephalopoda
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
Shell form and function
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
cephalopod locomotion
Forcefully expel water from the siphon -Mobile for directional control Squid very fast, cuttlefish slower, nautilus even slower, octopus usually crawl
46
cephalopod respiration
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
cephalopod nervous and senosry system
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
cephalopod communication
Visual signals extremely important -Body motions -Color changes through chromatophores Use ink gland for defense
49
cephalopod reproduction
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
cephalopod taxonomy
nautiloidea ammonidiea coeloidea
51
nautiloidea
one pair of gills only one surviving genus with 5 species
52
ammonoidea
all extinct in the cretaceous -before asteroid chambered shells with more developed septa
53
coeloidea
squids octopuses cuttlefish
54
Bilvalvia (Pelycopoda)
“Hatchet footed” animals Mussels, clams, scallops, oysters, shipworms Most are sedentary filter feeders Most marine, plenty freshwater Very important to humans
55
Bivalve shell form and function
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
bivalve Body, mantle,
Visceral mass suspended from dorsal midline, ctenidia hang on each side of foot Some clams have a mantle modified into long siphons
57
bivalve locomotion
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
bivalve Gills
Gas exchange occurs in both mantle and gills Some have modified these gills through lengthening of filaments, can interlock to form lamellae
59
bivalve feeding
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
bivalve internal structures
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
bivalve reproduction
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
Scaphopoda
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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