MOLLUSCA Flashcards
General Characteristics of Molluscs?
Foot, mantle, shell.
Marine, freshwater, terrestrial
Coelomate protostomes (Spiralia).
5 classes of Mollusca
Class Polyplacophora (chitons)
Class Gastropoda (abalone, sea slugs, sea hares, terrestrial slugs and snails)
Class Bivalvia (clams, mussels, oysters, scallops)
Class Scaphapoda (tusk shells)
Class Cephalopoda (nautilus, octopus, squid, cuttlefish)
What type of symmetry?
Bilateral
Reduced coelom but with an extensive _______ comprising an open circulatory system with compartmentalized heart.
hemocoel
What are the 3 body regions
head, foot, visceral mass
Define the Mantle
thick epidermal-cuticular covering that secretes the shell
What is housed within the mantle cavity?
ctenidia (gills), anus, opening to kidneys and reproductive tract, and osphradia (sense organs)
What is the radula?
a ribbon of recurved chitinous teeth that often functions as a scraper to remove food particles for ingestion
What controls the radula?
the odontophore
What type of kidneys?
Metanephridial
What type of larvae?
Trochophore and veliger
What stage does torsion occur in gastropods?
Veliger larvae stage
3 layers of the body wall?
cuticle, epidermis, muscle layers
How does water flow thru the mantle cavity?
driven by cilia
In cavity —> over gills —> over nephridiopores and anus —> out.
What are the 3 layers of the shell?
Three layers: periostracum made of scleretized proteins (conchin), prismatic made of CaCO3 in columnar conchin matrix, and nacreous made of CaCO3 with some conchin in sheet-like pattern (mother-of-pearl).
Which animals have reduced shells?
sea hares, squid pen, cuttle bone
Which animals have lost shells?
Octopus, nudibranchs
What happens during torsion on gastropods? What does it result in?
Rotation of visceral mass and overlying mantle and shell 180 degrees with respect to foot and head.
Gut ends up U-shaped and incipient organs are switched left to right.
How do gastropods and polyplacophorans move?
Crawling (direct and indirect waves)
Mucus alternately acts as a glue and allows sliding.
Some gastropods use cilia (moon snails).
How do Bivalves move?
Burrowing, byssal threads, swimming
How do Cephalopods move?
Radial and circular muscles. Contraction of circular muscles forces water out siphon or funnel for swimming.
Crawling along substratum.
Describe the Cephalopod nervous system
Well developed -
Brain with lobes.
Large nerve to all parts of body.
Large optic nerves.
Memory in octopus.
What do osphradia do?
chemosensory and sensing sediment
What do statocysts do?
balance and oreintation
What type of sense organs are tentacles and rhinophores?
chemosensory
What are chromatophores?
Cells for color change in cephalopods.
Contain pigments and are under neuronal and hormonal contol.
what is Macrophagy
eating “large” things
What is Microphagy
eating “small” things
How do gastropods eat?
using their radula
How do Cephalopods eat?
Cephalopods highly mobile predators.
Catch prey with suckered arms.
Neurotoxins associated with beak in octopus.
How do Bivalves eat?
Ctenidia modified for particle capture
What is the function of labial palps in Bivalves?
sorting food particles
What are pseudofeces? (Bivalves)
non-organic particles that are excreted (they never entered the digestive system - kicked out by labial palps)
Complete or Incomplete digestive system?
Complete
What is the purpose of a crop?
Food storage
What type of circ system?
Open - except for Cephalopods (closed)
How do terrestrial gastropods do gas exchange?
they have a “lung” - a vascularized mantle cavity
What kind of waste do aquatic molluscs excrete? terrestrial?
aquatic - ammonia
terrestrial - uric acid
Hermaphroditic or gonochoristic?
most gonochoristic (bivalvia, cephalopoda, gastropoda)
some hermaphroditic (simultaneous and sequential) (gastropoda)
What type of cleavage?
spiral
mouth from ______?
blastopore
cell fate determined early or late?
early
What type of development?
(direct, indirect, mixed)
can be all
terrestrials and cephalopods direct
nudibranchs mixed
what is the excretion organ?
paired tubular metanephridia
Those with indirect development - what type of larva?
Free swimming trochophore larva
