Molluscs Flashcards
Characteristics of Molluscs
- 200,000 species
- More species in ocean than any other animal group - Soft body enclosed by calcium carbonate shell
- Body covered by mantle
- Thin layer of tissue that secretes the shell - Occupy all marine environments – rocky shores to hydrothermal vents
Mollusca Structure
- Displays Bilateral Symmetry
- Ventral muscular foot used for locomotion
- Most had have that includes eyes and other sensory organs
- Some have radula
- Ribbon of small teeth used to rasp food from surfaces
- Made of chitin - Have paired gills
- Portion of body may be coiled and asymmetrical
*Class Gastropoda
radula
deposit feeders
carnivores
- stomach foot (most common mollusks)
- Snails, limpets, abalone, and nudibranchs.
- 75,000 spp.
- Most use _____ to scrape algae
- Mud snails are ______ _______
- Whelks, oyster drills, and cone shells are ______ that prey on clams, oysters, worms,
and small fishes
- Modified Radula to drill and rasp prey
*Gastropod - Nudibranchs (sea slugs)
nematocysts
- No shell
- Colorful branches of the gut and gills
- Prey on sponges and other invertebrates
- Produce noxious chemicals or retain undischarged ___________ taken undigested from prey
*Class Bivalvia
oxygen
filter feed
siphons
- Clams, mussels, and oysters
- Body laterally compressed and enclosed with two parts (valves)
- No head or radula
- Gills expanded and folded used to obtain ____, and filter and sort food particles from water
- Scallops also _____ _____. Many have striking color patters.
- Inner surface of shell lined w/ mantle so whole body lies in mantle cavity
- Strong muscles used to close valves
- Clams burrow in sand or mud and water drawn in and out of mantle by ____
- Allow clam to feed and obtain oxygen while buried
byssal threads
Class Bivalvia: Mussels secrete ___________ that attach them to rocks and other surfaces
left
CaCO3
Class Bivalvia: Oysters cement their ____ shell to hard surface and other to another oyster
- Pearls occur when irritating particles are lodged within the mantle cavity and
covered by secretions (______) from oyster
siphon
Class Bivalvia: Some scallops can swim by rapidly ejecting water from mantle cavity with _______.
mangroves
symbiotic
calcium carbonate and siphon
Fouling
- Shipworm bores in ________, driftwood, and pilings
- Have ______ relationship w/ bacteria in the gut that digests wood
- Valves lie at the inner end of tunnel lined w/ _______ _______ and _______
protrudes from entrance - ________ organism = settles on bottoms of boats, pilings, and other submerged
surfaces
*Class Cephalopoda (head footed)
locomotion
loss
- Predators specialized in _______
- Octopi, squid, and cuttlefish
- Agile swimmers w/ complex nervous system and reduction or _____of shell
- All are marine
Class Cephalopoda General Morphology
muscular mantle
jet propulsion
- Large eyes on side of head
- Thick ______ ______ which protects head
- Water enters mantel and leaves through siphon = ____ ________
*Cephalopod: Octopi
Bottom
beak-like jaws and radula
ink sac
Eight long arms (2 in to 30 feet)
_______ dwellers that live in crevices, bottles, etc
Have _____-_____ jaws and _______ to rasp flesh and secrete paralyzing substance
Distract predators with dark fluid from ____ ____
*Cephalopod: Squid
triangular
motionless
two
pen
- Two _______ fins on mantle – better swimmers than octopi
- Can remain ______, move forward, or backward
- Eight arms and _____ tentacles, all with suckers
- Has ____ in upper surface of mantle
- Few cm to 60 feet
*Cephalopod: Cuttlefish
Eight
flatten
buoyancy
- _____ arms and two tentacles, but body _______ w/ fin running along the body
- Have calcified internal shell aids in __________
*Cephalopod: Chambered Nautilus
gas
buoyancy
suckerless
- Coiled external shell containing ____ filled chambers serves as ________ organ
- Has _______ tentacles
*Other Molluscs: Polyplacophora
overlapping
shallow
radula
Chitons (class _________– bearer of many plates)
- All marine
- Eight _________ shell plates covering dorsal surface
- Live in ______ hard bottoms
- Have ______ to rasp algae
*Other Molluscs: Scaphopoda
Elongated
Sandy muddy
thin
- Tusk shells or scaphopods (class ___________)
- ________ shell tapered at end resembling elephant tusk
- _______ ______ bottoms in deep water
- Many species have _____ tentacles to capture small prey
ganglia
Biology of Molluscs: Nervous System
Gastropods and bivalves have ________ (local brains) located in different parts of body
*Cephalopods
coordinate and store
development
cuttlefish
color
behavior
Biology of Molluscs: Nervous System
- Most complex of invertebrates
- Brains _________ and _______ information
- Complex eye reflects __________
- Octopi and _______ can learn
- Display rapid ______ change coordinated with behaviors and moods, from sexual display
to camouflage
- Cuttlefish “flash lights” while octopi change color and ________ to mimic poisonous fish
and sea snakes
separate
sperm and egg
internal fertilization
transfer spermatophore
trochophore
Biology of Molluscs: Reproduction and Life History
- Most have _______ sexes (some hermaphroditic)
- Bivalves, chitons, tusk snails, and some gastropods release ______ and ____ into water
- Cephalopods and most gastropods – _______ __________
- Cephalopods – modified arm to _______ _________
- Develop in yolk-filled eggs attached to crevices
- Female dies – guarding eggs = no food
- Some have _________ larvae, displaying relationship to segmented worms
