Mollusca II Flashcards
What are gastropods?
-stomach feet creatures
-snails & slugs
-predatory
-herbivores
-not many parasites
-benthic or pelagic
-terrestiral, marine, or freshwater
-enormous diversity of marine animals are gastropods along with marine shells
What are the synapomorphies of gastropods?
-shells: coiled or spiraled. univalve, one half to their shell
-terrestrial gastropods have operculum. a proteinaceous door that seals the snail inside its shell. contains moisture and hide from predators
what distinct the gastropods from bivalves?
a distinct scar
What is evolutionary torsion?
long evolutionary process of going from untwisted descendants to twisted descendant is possibly due to drift
what is ontogenetic torsion?
- occurs in every individual snail during embryonic development
- embryo starts untwisted and as it grows it twists
- causes twisting of the digestive system
what does ontogenetic torsion cause?
fouling: excreting digestive system waste on your head
What is coiling?
-proudction of snail shells
-starts as a baby and secrets a shell every year that that grows in a spiral
-naturally selected because its directly related to survival and reproduction
-some snails appear to have their shells falling off their bodies
What are the two different types of shells?
planospiral and conical
what are planospiral shells?
- cinnamon roll appearance
- single plane
- rest inside the previous corals
- strong but not as strong as the concave apical shape
- weight distributed in the middle
what are conical shells?
- rings rest on top of each other for a conical formation
- can withstand more force
- as the coils are growing, the weight equilibrium is shifted
- causes the shell to move to the left or right to off center to get weight equilibrium
- causes the loss of gils, auricle, and kidneys
What do gastropods eat?
- a lot of them are herbivorous that eat plants , some are predators other animals
-terrestrial eats plants through the radula, supported by the odontophore - some are fungivores that eat fungi
How do gastropods breathe?
- respiration happens better across a wet membrane
- diffusion is quick across a wet membrane
how do water gastropods breathe
gills
how do terrestrial gastropods breathe
- they belong to a class called pulmonates that have pneumostomes
- highly vascularized, lots of blood vessels around the mantle cavity
- ability to open and close
- some pulmonates are aquatic that have a siphon, extension of their mantle wall that they use to breathe around water
How do gastropods reproduce?
- most pulmonates are monoecious
- cross fertilize
- find each through chemical signature that the tentacles pick up
- slaps feet together
- shoot each other at high pressure with darts from their sacs that are made of calcium
What are the two reasons why darts are shot from calcium sacs?
-sperm delivery mechanism: doesn’t make sense cause they both have penises and there’s no sperm on it
-nupital gift giving: better chance of having a good shell and for protection but they both
What is the real reason that they shoot calcium spears?
-the calcium spear has a hormone that shuts down the sperm destruction path and opens the sperm storage path
Why are gastropods usually placed?
- a moistened area
- in a rotten log or under a leaf
- usually abandoned
- when hatched they look like miniature adults
- called direct development because there is no metamorphosis or larva, just egg
What are prooobrancia?
marine shelled snails
what are Opisthobranchia
unshelled marines
what are Pulmonata
usually terrestrial
what are bivalves?
- oysters, clams, scallops, mussels
- largest one is the giant claims
- sessile water filters
- brings water in extracts oxygen and food as it passes over gills
- incredibly good at filtering water
How do bivalves close and open their shell?
- uses antagonistic forces to move
- close shell: adductor muscle contracts
- hinge ligament stretches to store potential energy
- open shell: adductor muscle relaxes
- hinge ligament snaps back to open
What is the anatomy of a bivalve?
- foot anchors into the sand/soil
- water flows into the incurrent siphon
- water flows out of the incurrent siphon
- water pulled by the cilia
Describe the bivalve physiology
-has crystalline style, gelationous rod inside the stomach that helps with digestion mechanical and chemical
- scallops have rows of eyes are filled with crystalline proteins that reflect light like mirrors
- uses eyes to swim away from predators
- good swimmers
How do bivalves eat?
- filter feeding
- two exceptions
- giant clam: harbors symbiotic zooxanthellae in its mantle, and also photosynthesizes
- shipworms: unshelled organisms that digest wood
- has endo- symbitotic bacteria to break down cellulose
How Bivalves move?
- uses their muscle to open the shell, water rushes in, and then they close the shell fast to cause the water to pulsate out
- some don’t move such as mussels
- uses byssal threads
- a liquid but when it contacts sea water it turns into a hard cement like protein glue
