Mollusks Flashcards
What is a mantle?
a layer of tissue that lies between the **shell **and the body.
What is the foot?
the underside used for movement.
What are the main features of Molluska?
Huge size range
* **Bilateral **symmetrical
* Unsegmented
* Protostomes
* Complete gut
* Large complex
nephridia (most)
* remove metabolic
wastes
What is a radula?
tongue with scraping
teeth used for feeding
What is ctenidia?
a respiratory organ or gill in a mollusk with filaments
How do ctenia function?
Food particles are trapped in mucus on gills and transported to mouth
What type of larvae do mollusks have?
trochophores
What are the classes of mollusks?
-Bivalves
-Gastropods(snails and slugs)
Cephalopoda(octopus)
Scaphopoda (Tusk shells)
Aplacophora (marine vermiform molluscs)
Polyplacophora(chittons)
What are the characteristics of bivalves?
Two shells (valves)
* ~20,000 species at all depths
* Mostly **sessile filter feeders
* Usually separate sexes
* No “head” or radula**
* Laterally (right-left)
compressed
– held together by a hinge
ligament
re the
What is an umbo?
oldest part of the
shell, growth occurs in
concentric rings around it
What are siphons used for?
Used to pump water
through the organism
for gas exchange and
filter feeding.
– Sometimes used for jet
propulsion
How do bivalves move?
extending the muscular
foot between the
shells.
How to scallops move?
clapping their shells
together to create jet
propulsion.
What is the largest class of mollusks?
gastropods
What are characteristics of gastropods?
Marine, freshwater,
terrestrial.
* Benthic or pelagic
– Not all have shells
What is torsion?
a developmental process
How does torsion function?
– After veliger settles
– Body twists into permanent** loop**
– **Rearranges organs **and **brings **them together
How do herbivore gastropods eat?
most are herbivores
Scrape off algae with Radula
How do scavenger gastropods eat?
Tear off pieces with radular teeth
How do canivorous gastropods eat?
Modified Radula to drill hole in
shells and eat other mollusks Via chemicals
How do snails in the conus family eat
fish, worms, and molluscs.
– Highly modified radula used for prey capture.
– They** secrete** a toxin that paralyzes their prey.
* Some are painful, even lethal, to humans.
What are Prosobranchia ?
snails with gills in front of heart
What are Opisthobranchia
Snails with gills behind their heart.
What is an example of Opisthobranchia
nudibranchs
What is an example of Prosobranchia?
Spirally coiled
shell
What are Pulmonata
land snails and slugs
How do Pulmonata reproduce?
-Dart sac secretes calcareous dart (harpoon)
* During courtship dart is poked into body wall of the other snail
What are the features fo gastropod and bivalve circulation and gas exchange?
Open circulatory system
* Heart with atria
* Hemocoel – body cavity
What are Polyplacophora?
chittons:
elongated with 8 plates
What are Scaphopoda?
tusk shells
What are Aplacophora
marine vermiform molluscs
What are the main features of cephlapods?
-beak-like jaws surrounded by tentacles of their modified foot.
– Modified foot is a **funnel **for expelling water from the mantle cavity.
- Ink sacs
What are examples of cephalopods?
octopus, squid, nautilus
What were early cephlopods like?
Fossils go back to** Cambrian** (570 mya)
* The** earliest had straight cone-shaped shells.
* Later examples had coiled shells similar to Nautilus**.
How does a nautilus shell become buoyant?
made buoyant by
a series of gas
chambers
How are cuttlefish shells formed?
a small curved shell, completely enclosed by
the mantle
How are squid shells formed?
reduced to a small strip
called the pen, which is enclosed in the mantle
What is the circulatory system of cephlapods?
closed
how many hearts do celphlopods have?
1 systemic
2 branchial
What is jet propulsion?
when the animal **takes in water **through its mantle. The water is then **pushed **through the siphon
What are chromatophores?
cells in the skin
containing pigment
granules
allow color change
How do cephlopods reproduce?
One arm of male is** modified** to removes a spermatophore from mantle cavity and inserts it into
female
