Midterm 2 Flashcards
Mollusc key characteristics
- Visceral Mass
* Head- foot
The Head
- Feeding
- Sense organs
- Brain, eyespots-to-eyes, tentacles
The Radula
- Part of the Head-Foot
- Chitinous ribbon of teeth
- NOT in any Bivalve
- Odontophore cartilage holds teeth
- Muscles move it in and out
- Muscles to move odontophore and muscles to move radula
The Foot
Locomotion, attachment
Ventral
- Visceral Mass
- Internal organs
- Digestive, excretory, reproductive and respiratory
contains mantle and mantel cavity
- Digestive, excretory, reproductive and respiratory
Mantle
- the “skin”
* Can have muscles, or chemoreceptors, etc
* Makes the shell
- Mantle Cavity
open to “world”
* Excretion (metabolic and digestive), respiration, reproduction
- Periostracum
- Outer organic layer (resistant protein conchiolin)
- Prismatic layer
- Calcium carbonate stacks
- Nacre
- Continuously thickens
- Calcium carbonate + protein sheets
Pearls
- Calcium carbonate + protein sheets
Mantel layers
Nacre
Prismatic layer
Periostracum
Reproductive System of Molluscs
- Never asexual
- Diocieous or monoecious
- Trochophore larvae in most
- Veliger larvae common
- Aquatic Bivalves and Gastropods
- Some have direct development (no larvae)
The Aplacophorans
- Contains classes Caudofoveata and Solenogastres
- Wormlike and shell-less
- Calcareous scales/spicules
- Marine detrital/microorganism consumers – burrowers!
Class Monoplacophora
- Means one plate
- Thought to be extinct until 1952!
- Round shell, large foot
- Serial repetition of body parts
- Gills, nerves, gonads, nephridia…
Class Polyplacophora
- Means many plates” – the chitons
- 8 moveable plates
- Mantle girdle around outside
- Intertidal rocky areas
- Serial repetition seen
Class Scaphopoda
- Tusk shells/tooth shells
- Sedentary
- Tubular shell (open at both ends)
- Tentacular foot for burrowing and food capture
- A lot of diffusion in mantle cavity
- No heart, no gills..
Class Gastropoda
- Means stomach foot
- Most taxonomic rich (diverse) class – 60,000+
- Snails, periwinkles, limpets, sea slugs, slugs
- Marine, freshwater, terrestrial
- Coiled shell, domed shell, no shell
- 3 Main groups of Gastropods
- Prosobranchia
- Most marine snails (periwinkles, limpets, conchs…)
Gastropods
- Opisthobranchia
Gastropods
* (mostly) marine shell-less forms (nudibranchs, sea slugs...) * cerrata
- Pulmonata
Gastropods
* Most land and freshwater snails and slugs (mantle cavity into lung)
Torsion
180 degree rotation of the mantle/mantle cavity, internal
Coiling
whorling of the shell
- Feeding Gastropods
all feed with some adaptation of the radula
Gastropods reproduction
- Simultaneous hermaphrodites * Eversible penises and simultaneous sperm transfer
- Love Darts and Slug Orgies
Class Bivalvia
- Laterally compressed shells
- Hinged dorsally; gape open ventrally
- Means two valve
- No head, no radula
- Bivalve locomotion
- Foot to burrow (clams)
- Adductor muscles to swim (scallops)
- Some sessile
- Byssal threads (mussels)
- Cemented (oysters)
Class Cephalopoda
* Means head-foot
predators
* Exclusively marine
* Most have 1 pair of gills
8 arms (2 tentacles for squid and cuttlefish)
* Closed circulatory system
* Incredible nervous systemChromatophores
Cephalopoda. Camouflage cells 4 types
Cephalopoda Reproduction
- Dioecious
- With some amazing mating rituals!
- Copulation
- Direct development (no larvae)
- All but a couple species die
Conchiolin
found in outermost layer of mantel shell (Prperiostracum)
