Molluscs Flashcards
What is the human importance of molluscs
Food (calamari, mussels, scallops, clams)
Pearl + shells
Bio-indicators
Biotech (bullet proof veste)
What are the two important features that make a mollusc a mollusc?
Visceral mass
Head foot
What is the head foot used for in molluscs
Sensory snd locomotion
Where is the radula found in molluscs?
Head foot
What is the radula in molluscs?
Chitinous ribbon teeth
Held together by odontophore cartilage
Ribbon teeth move over cartilage
Odontophore can move in and out
What is highly modified among the different classes of molluscs, found on the ventral side and used primarily for locomotion?
Foot
What is the visceral mass of molluscs?
Mantle + mantle cavity
The skin that wraps around the body and protects the soft parts of the mollusc, extending from the visceral mass, is called what?
Mantle
What part of the visceral mass makes the shell
Mantle
What are the three layers of the mantle and shell
P-P-N
- Peristracum
- Promatic
- Nacre
What layer of the shell is the outer organic proteinaceous layer?
(Skin of shell)
Peristracum
What layer is the thickest with lots of calcium carbonate stacks that are in a proteinaceous matrix?
(Some of the strongest material on earth)
Prismatic
What is the nacre layer of the shell?
Shiny + smooth inner layer
Continually laid down
Where pearls are made
What is nacre made out of?
Calcium carbonate + protein sheets
How is a pearl made?
Debris gets btw shell + mantle sand)
Nacre lays down overtop debris
Makes pearl
Molluscs
Symmetry?
Body cavity?
Bilateral
Coelomates
Can molluscs be asexual
No
Male, female or hermaphroditism
What kind or larvae do molluscs have?
Aquatic larvae or gastropods = TROCHOPHORE LARVAE
some have veliger larvae
Some direct development (cephalopods + snails)
What kind of larvae to cephalopds and snails have?
Direct development
What are the 8 classes of molluscs?
Aplacophorans (combo of 2 classes) Bivalvia Cephalopods Gastropods Monoplacophora Polyplacophora
The aplacophorans are a combination of 2 classes of mollusc… what are they
Causofoveata + solengastres
What class of molluscs is worm like, NO SHELL + NO FOOT and is a marine burrower with calcareous scales/spicules?
Aplacophorans
What are some key characteristics of class monoplacophora?
One plate
Rounds shell
Big foot
Plates repeat
What class are many repeating internal and external strucutres (gills + nerves) and is kinda like the molluscs armadillo because of its many plates (8 movable plates)
The polyplacophora
What class are the chitons under in molluscs?
Polyplacophora
What is indicative of class scaphopoda?
Tusk shells / tooth shells
Tubular
Modified with tentacles
- sticky ends = captacula!!!
NL HEART + NO GILLS
What class has no heart and no gills (molluscs)?
scaphopoda
What group of the gastropods is mostly marin snails like periwinkles, limpets and conchs?
Prosssssssss…
Prosobranchia
Pros bra
Opisthobranchia are what type of gastropods..
Shell less, marine
Nudibranchs and sea slugs
Do nudibranchs and sea slugs have gills and shell?
No, because they are part of opisthobranchia group of gastropods
What group of gastropods have cerrata (dorsal extensions along mantle edge)?
Opisthobranchia
Most land and fresh water snails belong to what group of gastropods or phylum mollusc?
Pull mon
Pulmonata
Whats the difference btw torsion and coiling in gastropods?
Tosrsion = 180 deg rotation of mantle (anus and gills)
Coiling = whorling or shell
Head near butt
The cone snail is an example of a unique feeding method of the gastropods… what feature is usually highly varied to make gastropod feeding so unique
Radula
How do gastropod hermaphrodites who are marine differ from hermaphrodites who are on land?
Marine = veliger larva
Land = protective egg cases
Gatropod reproduction - explain simultaneous hermaphrodites
Mating rituals - build pressure for LOVE DART
copulatory organs in head
Love dart = eversible penis + vagina
They stab each other in the head
Are gastropods monoecious dioecious or hermaphrodites?
All three
What has no radual, no head, just two valves and a laterally compressed shell
Class bivalvia
Sedentary suspension feeders of class bivalvia have gills covered in… and use what to help direct water flow
Ciliated mucus covers gills
Siphon for water flow
What features to burrowing forms of bivalves (like clams) have to keep water flow even when burrowed
Large muscular foot on anterior/ventral
Siphon on posterior
Keeps water flow even
What is the oldest part lf the bivalves shell and what does this part do?
Umbo
Where hinge is - where it grows from
Dorsal side
What muscles open and closes the shell in class bivalvia?
Abductor muscles
What does the term ctenidia mean in bivalves?
Gills
Where are the gills of bivalves found? What are they covered in?
Dorsal side
Covered in mantle sheath
How are gills used for feeding and respiration in bivalves?
Particles come in posterior’
Go along cilia tracts of gills
Sand rejected out ventral side
Food goes to anterior end where palps turn it into bolus
How to clams move differently than scallops? what about sessile bivalves like mussels and oysters?
Clams = burrow
Scallops = clap and swim with abductor muscles
Mussels = byssal threads
Oysters = cement to substrate
Nautiloids, cuttlefish, squids, octopuses belong to what class of mollusc?
Cephalopod
What type of cephalopod has a large shell, lives in outer most shell layer but regulates the gas pressure with its SIPHUNCLE?
Nautiloids
What kind of shell do cuttle fish have? What about squids? Ocotpuses?
Cuttle fish = internal shell enclosed by mantle
Squids = pen (dorsal) enclosed by mantle
Octopuses = no shell
Cephalopods - how do they move?
Jet propulsion
- muscle walled mantle contracts
- water shoot out siphon
- animal shoots backwards
What is the basic body plan of cephalopds
1 pair of gills
8 arms - suckers / hooks
Closed circulatory system
Nervous system + eyes
How to the chromatophore cells help cephalopds camouflage?
Change colour by getting bigger or smaller in diameter
What do the ink sacs of cephalopods contain? Where are the ink sacs found?
Melanin + sometimes mucus
Rectum
What class of mollusc is exclusively dioecious?
Cephalopods
How do cephalopds reproduce?
Sperm passed in packets to females
Fertlized eggs leave females, laid on rocks
She protects them
Do cephalopds have a larval stage? If yes, what type of larva?
No larvae
Direct development
What is meant by cephalopds are semelparous?
Die after mating
What are the 5 key body transitions of molluscs?
O - organ S - bilateral BC - eucoelomate D - triploblast/protostomes/lophotrochozoa Segmentation - no
