BIOL 2003 Lecture Notes - Lecture 8: Colossal Squid, Odontophore, Cosmopolitan Distribution
Phylum: Mollusca
September 30 & October 5, 2015
• Extremely diverse (85000+ species) and disparate (8 groups)
• Marine, freshwater, terrestrial (cosmopolitan distribution)
• Carnivores, herbivores, filter feeders, parasites
• Most are small (<10cm) but are also some of the biggest invertebrates (colossal squid)
• Ex. Snails and zebra mussels live in fresh water
• Gastropods – exclusively in marine, freshwater and terrestrial
• Human Importance:
1. Food
• Calamari, escargot, mussels, scallops, clams
2. Pearls and Shells
• Cowries = currency
3. Bioindicators
• Environmental indicators and filters (invasive species, ecosystem
changes)
4. Pests
• Bites, stings, crops, parasites, fouling
5. Biotechnology Importance
• Nerve cells and axons; shell strength
What makes a mollusc, a mollusc?
1. Visceral Mass (all internal organs including mantle)
o Internal organs: digestive, excretory, reproduction and respiratory systems
o Mantle & Mantle cavity:
o Mantle = the skin **makes the shell
▪ Can have muscles or chemoreceptors
o Mantle cavity = open to World
▪ Excretion (metabolic & digestive), respiratory and reproduction
products enter outside
o Mantle and the Shell:
o Made by outer layer of mantle
o Three layers:
1. Periostracum
o Outer organic layer (resistant protein conchiolin)
2. Prismatic Layer
o Calcium carbonate stacks (middle of shell)
3. Nacre
o Continuously thickens
o Inside of shell; shiny
o Calcium carbonate + protein sheets to protect mantle and
inside of the body
2. Head-Foot
o Head: feeding, sense organs (brain, eyespot-eyes, tentacles)
o Radula: chitinous ribbon of teeth
o Not in any bivalve
o Odontophore cartilage holds teeth – muscles move it in and out
o Muscles move odontophore and muscles move radula
o Foot: locomotion, attachment
o Always on ventral surface/side
o Use mucous to help glide and propel themselves *think about land snails
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
What makes a mollusc, a mollusc: visceral mass (all internal organs including mantle) Pearls: pearls form as intrusion between shell and mantle that becomes layered with nacre, cultured pearl: large nucleus in middle *usually rounder. Reproductive system: never asexual, dioecious or monoecious, trochophore larvae in most, veliger larvae common in aquatic forms. Classes: caudofoveata and solenogastres (the aplacophorans: worm-like and shell less, calcareous scales/spicules, marine detrital/ microorganism comsumers, burrow into sediment, reduced heat; no foot. Class: monoplacophora: one plate, thought to be extinct until 1952, round shell, large food. Series of repeated body parts (gills, nerves, gonads, nephridia) Class: polyplacophora: many plates the chitons (8 moveable, mantle girdle around the outside of their body. *could have been a segmented creature in past. 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 or gills.
