Mollusca Flashcards
mantle definition
thin fleshy sheath hanging down either side of body
mantle cavity
encloses gills or serves as “lungs” ; products of digestive excretory and reproductive are brought here
trochophore
simple free-swimming feeding larval stage
Veliger
complex free-swimming feeding larval stage
Torsion
during embryonic development body is twisted 180 degrees, orienting anus anteriorly
Glochidium
specialized veliger larva, parasite/disperses on fish gills, scales
What are the general characteristics of phylum mollusca?
- eucoelomate: coelom lined with mesoderm
- foot: locomotion
- mantle: pair of thin body folds (cape)
- radula: rasping mouthpart
- open circulatory system (closed in cephalopods)
- respiration: cutaneous, gills, or vascular mantle (“lungs”)
- organ system level of organization
- extracellular digestion of food
what are the 3 layers that make up the shell of a mollusk?
periostracum, prismatic, and nacreous
what are the characteristics of periostracum layer?
resists acids, attack; camouflage
what are the characteristics of prismatic layer?
calcium carbonate for strength
what are the characteristics of nacreous layer?
smooth mother-of-pearl to protect soft body
what are the characteristics of the open circulatory system of molluscs?
- blood oxygenated in gills and mantle
- goes to paired auricles (atria) of heart -> muscular ventricle (3 chambers)
- tissues bathed within coelom
- blood collected and pressure boosted by accessory hearts in front of each gill
What mollusks have a juvenile stage rather than larval stages?
cephalopods
what mollusk is in the polyplacophora class?
chitons
what are the characteristics of class polyplacophora?
o dorsoventrally flattened
o 8 overlapping protective plates on top
o Broad foot beneath
o Clings to rocks, scrapes algae
what is the food of class polyplacophora?
algae
what mollusks are in class gastropoda?
snails, slugs, limpets, periwinkles, conchs, whelks, sea slugs, abalone
what are the characteristics of class gastropoda?
o most diverse
o terrestrial forms
o coiled univalve shell (or absent)
o torsion (during embryonic development body is twisted 180 degrees, orienting anus anteriorly
what are the feeding methods of class gastropoda?
o herbivorous (grazers of algae, plants)
o scavengers
o suspension/filter feeders (trap food particles in mantle mucous)
o carnivorous
what mollusks are in class bivalvia?
clams, mussels, scallops, oysters, shipworms
what are the characteristics of class bivalvia?
o two laterally compressed shells/valves
o no head or radula
o glochidium - specialized veliger larva, parasite/disperses on fish gills, scales
what are the feeding methods of class bivalvia?
o filter feeding
food trapped by mucous covered gills
cilia carry to labial palps -> mouth
shipworms rasp wood with shell
* bacteria in gut provide cellulase
what is the locomotion of class bivalvia?
foot extended -> burrows in sand -> swells with blood and anchors -> body pulled forward
what are the mollusks in class Cephalopoda?
squid, octopus, cuttlefish, nautilus
what are the characteristics of class cephalopoda?
o structure:
most no shell
a narrow internal chitin strip (pen) or cuttlebone protects ganglia
o foot modified as arms/tentacles in head region
o jet propelled – water forced out funnel head
o highly predatory
advanced eyes, brain, arms/tentacles, beak
o advanced social communication
chromatophores change color rapidly
o reproduction
male places spermatophore in female using specialized arm
fertilized eggs attached to stones
o closed circulation
describe the role of a clam’s gills in respiration.
Cilia create water current -> incurrent siphon -> gills -> outcurrent siphon
describe the role of a clam’s gills in feeding.
Food trapped by mucous covered gills -> cilia carry to labial palps -> mouth
