Ch 9-11: Mollusca Flashcards
5 tree features of Phylum Mollusca
- bilateral
- excretory system
- protostomes
- lophotrochozoa
- trochophore larva
7 defining features of Mollusca
- soft-bodied
- dorsal epithelium forms the mantle
- ventral body wall muscles form the muscular foot
- mantle cavity contains gills/ctenidia
- have a radula
- small coelom
- open circ system
2 features of the mantle
- secretes CaCO3 spicules/shells
- drapes over visceral mass
what is a radula
file-like feeding structure
open circ mechanics
several sinuses that join to form a hemocoel
3 layers of the shell (outside in)
- periostracum
- prismatic layer
- nacreous layer
periostracum features (2)
- mostly made of protein
- protects the inner layers from acids
prismatic layer features (2)
- made of CaCO3 and protein
- thickest
nacreous layer features (2)
- scales of CaCO3 in proteins
- iridescent
how many shells do Polyplacophora (Chitons) have on their dorsum?
8
where would calcerous spicules on a chiton be located if they had them?
girdle
chiton speed
slow
when do chitons feed
nocturnal grazers
what are chitons famous for
super muscular foot, hard to pull from rocks
how many pairs of ctenidia can chitons have, and where are they located?
up to 90 in their mantle cavity
which direction do cilia move w
anterior -> posterior
what kind of gut do chitons have
thru
why might chitons need large digestive glands and a well-developed radule?
must prod enzymes to break down cellulose as they are herbivores
advantage of countercurrent exchange at ctenidia in chitons
diffusion can occur all the way down the mantle; no eq reached
how does blood return to chitons vessels?
via sinuses
what compound helps bind O in chitons?
hemocyanin
where might you find chitons pair of excretory organs?
in a sinus or coelom
chiton nervous system (4)
- anterior ring around gut
- 2 lateral
- 2 medial nerve cords
- no brain
what type of eyes do chitons have and where
ocelli, some have lensed eyes; on the dorsum
where are chitons gonads located
dorsal side
what 2 things do Aplacophora NOT have that most other Molluscs have
- calcerous spicules
- obvious foot or mantle cavity
4 features of Aplacophorans
- mostly deep w
- usually < 5cm
- live on/in sedi
- eat cnidarians, annelids, foraminifera
Monoplacophora feature
thought extinct, rediscovered, now only in deep w (outcompeted)
gastropoda shell
single, spiral
what way do most gastropod shells spiral
to the right
where is the operculum in gastropods located and what is its funct
foot; trap door
two features of gastropods that show their greater cephalization
- distinct head with two eyes and sensory tentacles
- distinct ganglia that sometimes form a ‘brain’
what is torsion
visceral mass and nervous system of adults twisted 90-180 deg anticlockwise
when does torsion occur
embryonic development
what is the result of torsion in gastropods?
anus and mantle cavity is above the head
2 adv of torsion in gastropods
- allows head to be pulled in 1st
- foot comes in last, leaving the operculum @ the door
2 other defenses of gastropods
- accumulation of distasteful compounds
- can smell nearby predators or wounded spp and move away
osphradium
a chemoreceptor for smell in the mantle cavity of a gastro
subclass prosobranchia holds mostly ? spp
marine
prosobranchia are 50/50 herbivores and predators. predators have 3 adaptations that help them
- a drill-like radula
- venom delivered by a hollow radular tooth (harpoon)
- tube-like ext of the mantle called the siphon that is used to sample scents
do opisthobranchs have shells
nope
do opisthobranchs perform torsion
no
what is different about the way opisthobranchs perform gas exchange?
no ctenidia; gas exchange via cerata
what are cerata
horn-like dorsal projections from the dorsum
rhinophores
a pair of sensory tentacles on the dorsum, potentially the same as the osphradium
3 ways opisthobranchs defend themselves
- carry chemical defenses
- toxic colouration
- acquired nematocysts
opisthobranchs and photosynth (2)
- some acquire photosynth symbionts
- Elysia chlorotica IS photosynth
pulmonata subclass resp (2)
- breathe air using the folded mantle cavity as a lung
- mantle cavity opens to outside via a pore called a pneumostome
pulmonata sex
hermaphrodites w/ complicated sex lives
shelled pulmonates lack a ? but use a mucus plug instead
operculum
what do bivalva have instead of radula?
siphons
what do bivalves use to dig into substrate?
their muscular foot
where are bivalves 2 shells hinged
at the mid-dorsal line
the 2 shells of a bivalve are connected by a protein ligament that, when relaxed, tends to open the shells. what does this mean?
only need muscles to close them - adductors
muscle scars =
attachment points of the adductor muscles in a bivalve
what does the pallial line mark
the edge of the living mantle
what does the pallial sinus mark
the region into which the siphon is withdrawn
what type of bivalve might not have a sinus
epifauna
umbo
a dorsal bump that marks the oldest part of the shell
5 steps to bivalve feeding
- cilial action pulls w into incurrent siphon
- suspended particles caught by mucus on ctenidia
- cilia move mucus to gill edges and forward to the mouth
- labial palps sort food
- enters mouth as a mucus string w/ the captures plankton
what is the function of a crystalline style
rotating gelatinous red that releases enzymes thru erosion that help digest the food; may also rotate and twist mucus into the digestive tract
where do wastes exit bivalves
anus; excurrent siphon
where is a bivalve heart kept
in the coelom, in a dorsal, fluid-filled pericardial cavity
bivalves have no blood pigment. what does this mean?
they are less efficient at transporting O2 in the blood
what fluid are the 2 metanephridia below the heart of bivalves filtering?
interstitial fluid
bivalves don’t have much cephalization or need for it, but they do have ? pairs of ganglia that coordinate different regions
3
what 3 nervous system features do bivalves have
- statocysts
- chemosensory cells
- simple eyes, scallops have lensed eyes
bivalve sexes
separate
what is a bivalve veliger
a type of intermediate larval form between trochophore and adult
how is freshwater fert different that marine fert in bivalves?
eggs held interior to females gills; sperm swim to them - less chance of loss
glochidia, freshwater bivalve larvae, are sometimes ?
ectoparasites
what do epifaunal bivalves attach to the substrate with?
byssal threads
how are the shipworms unique? (2)
- need wood to complete their lifecycle
- two shells @ head and extra cell-like structure @ bottom
what do Scaphopoda use to find food?
tentacles probe sand
where do scaphopods perform gas exchange?
folded mantle cavity
2 unique features of scaphopods
- shell open at both ends
- no eyes
what type of predators are squids?
high speed
what type of predators are octupuses?
bottom and crevice hunters
what type of predators are nautiluses?
scavengers, bottom hunters
5 feat of cephalopods
- carnivores
- marine
- foot modified into arms and a funnel like siphon
- closed circ system
- may have radula
are ammonites alive today?
nope; extinct at the end of the Cretaceous
decapods anatomy (2)
- 10 arms w/ suckers
- 2 long arms for catching prey
decapod mouth features (2)
- chitinized jaws bite off food chunks
- radula reduced; toxins ?
decapod shell features (2)
- reduced and buried in the mantle
- made of protein and may contain chitin
what has the shell become in a squid?
a pen
what has the shell become in a cuttlefish?
a bouyant cuttlebone
ink functions (2)
- distraction/smoke screen
- affects chemoreceptors of predators
how are decapods and octopuses able to change colour?
chromatophores expanding and contracting
decapod photophore funct
attracting prey, mates, enemies of predators
why are decapods more active in cold w?
cold w can hold more DO than warm
how do decapods circ w for resp?
pumping of the mantle
how many hearts do decapods have?
3 -1 systemic and 2 brachial
why would decapods have hemocyanin, which has a low O2 affinity?
O2 is easily released at the tissues
decapod brain type
large, lobed, encircles the esophagus, protected
nerves on decapod arms (2)
- long, thick neurons
- tactile receptors
2 other nervous system features of decapods
- olfactory organ
- 2 statocysts
what type of eyes do decapods have?
lensed; can form images
what is unique about decapod mating
courtship rituals
why do decapods have courtship rituals? (2)
- ensures that they are members of the same species
- way of gauging quality of potential partner
what is unique about the way that decapods fert
internal open fert; occurs in the mantle cavity
hectocotylus
modified arm used for transfer of spermatophore
which stage do decapods disperse in?
direct developmental tiny babies that are planktonic
extinct Belminite features (3)
- fossils of squid-like features
- hard/bullet-like internal shell
- survived the Cretaceous extinction but disappeared shortly after
octopoda arm features (2)
- 8
- suckers all the way down
octopoda shell
gone
3 reasons a female octopus may fan her eggs
- oxygenation
- keeps off algae
- agitation may help hatchlings emerge
who do Nautilus look like?
ammonites - spiral shell w/ air pockets
difference btwn ammonite and nautilus septa
ammonite septa are squiggly to accomodate for higher pressures; nautilus’ are smoothly concave
siphincle
tube that connects the chambers in a nautilus shell
how do nautilus control their place in the water column
ratio of l:g in old chambers affects bouyancy
how many tentacles do nautilus’ have? are they retractible?
90; yes
