1. Introduction to recipe of
Ch 27: Phylum Mollusca
Introduction to recipe of
grilled squid, tako,
oysters…etc

2. Outline Forms Feeding Respiration Internal Transport Excretion
Reproduction
Response
Ecological roles
Evolution

3. Introduction to Mollusks
Higher Invertebrates (smarter!!!)
Total of 7 classes
More than 112,000 species
They are found almost anywhere
Ex. Ocean, mountains, trees, etc.
Size ranges from a grain of sand to a giant squid (20 m)

4. Kraken A huge sea monster in Norwegian legend.
- Originated from sighting
of giant squid.
here have been claims reported of specimens of up to 20 m (66 ft), but no animals of such size have been scientifically documented. On September 30, 2004, researchers from the National Science Museum of Japan and the Ogasawara Whale Watching Association took the first images of a live giant squid in its natural habitat.[1] Several of the 556 photographs were released a year later. The same team successfully filmed a live giant squid for the first time on December 4, 2006.[1]

5. What is a Mollusk?
Soft-bodied animals that have an internal or external shell. (except few, such as octopus)
Trochophore, a special
kind of larvae. (Annelids
have it, too!!  common
ancestor)

6. Forms Four basic parts of (most) mollusks:
Foot: soft and muscular, contains mouth, comes in different shapes. (ex. Flat or tentacles)
Mantle: thin, delicate tissue that covers most of a mollusk’s body.
Shell: made of CaCO3 (calcium carbonate) secreted from glands in the mantle.
Visceral mass: contains the internal organs

8. Feeding Herbivores, Carnivores, Filter feeders, Detritus, or parasites
Complete digestive system (mouth to anus)
Radula: tongue shaped feeding structure, with hundreds of tiny teeth (feel like sandpaper!!!)

9. Respiration HOW? It depends… Aquatic mollusks use GILLS
(**Some have lungs)
Land mollusks use special adapted mantle cavity that is lined with blood vessels.
*must stay in a moist environment”
Use pics

10. Internal Transport Nutrients are carried by the blood to all parts
Open Circulatory System
Blood is pumped by a simple heart, the blood travels through body tissues in open spaces called sinuses, then to tissues -> gills -> heart
Good for slow moving mollusk (ex. snails and most other mollusks)
Closed Circulatory System
The blood always travels inside blood vessels.
Good for fast moving mollusk (ex. squid & octopus)

12. Excretion Solid waste leaves through ANUS in the form of feces.
Liquid waste, ammonia, which is a nitrogenous waste, is removed by NEPHRIDIA.

13. Reproduction Sexes are separated and fertilization is external
Ex. Most mollusks (some snails & 2-shelled mollusks)
Some release enormous #’s of eggs and sperms into open water
Internal fertilization in females
Ex. Tentacled Mollusks and some snails
Hermaphrodites
Snails
Switch sexes
Oysters

14. Response Varies greatly Simple Nervous System
Several small ganglia, few nerve cords, and simple sense organs (Ex. Clams & 2-shelled mollusks)
Statocysts: simple organ for balance
Ocelli: eyespots
Highly developed nervous system
Numerous complex sense organs (Ex. Octopus & tentacled mollusks) (EX. EYES)
Why simple ?

15. Their Ecological roles in our Society
Positives:
Important source of food
They are used to warn biologist about public health, b/c bivalves (filter feeders) may have “filter” dangerous pollutants.
Research for cancer prevention
Negatives:
Damage to garden and crops (slugs)
Poisonous bivalves
Shipworms destroys wooden boats, and docks.

16. Evolution Early Cambrian period (530 mi yrs ago)
First fossil of mollusk
Ordovician period (480 mi yrs ago)
Classes Gastropoda, Bivalvia, and Cephalopoda had increased greatly in number and diversity
Triploblastic protostome: During the first opening of embryonic development, the blastopore becomes the mouth.
Coelomates: true coelom, which means body cavity that is completely lined with mesoderm. More ADVANCED (comparing to Acoelomate and Pseudocolemate.

17. Evolution (contin’d) Bilateral Symmetry
It is believed that the ancestors of the octopuses and squids – shelled mollusks – lost their shell in later evolution to adapt to a predatory life style

19. The 3 Classes of Mollusca
Group 1: Class Gastropoda
Snail / Slugs
Group 2: Bivalvia
Clams / Oysters
Group 3: Cephalopoda
Squid / octopus

20. Instructions: For each GROUP: Divide into 3 little groups
Answer the following:
1) The characteristics of your Class
2) Common strategies of defense
3) At least 2-3 specific examples (including defensive strategy)
Group 2: describe how pearls are formed!!!

21. Class Gastropoda

22. Class Gastropoda Gastropods (slugs, snails)
Move by means of broad, muscular foot located on the ventral (stomach) side.
One-piece shell for protection
Ones without shells are protected by behaviours
Land Snails: hiding during daytime
Sea Hares: produce ink
Sea butterflies: escape by swimming rapidly
Nudibranch: poisonous / bad taste chemicals

23. Class Bivalvia

24. Class Bivalvia Bivavles (clams, oysters, mussels)
Two shell hinged together at the back and held together by 1 or 2 powerful muscles
Free swimming or burrow in mud/sand
Scallops: flap their shells to escape when threatened
Clams burrow in sand
PEARLS: a tiny foreign object traps between mantle and shell, the mantle glands secretes a layer of “mother-of-pearl” secretion. Years later, VOILA~ Pearls!!!

25. Class Cephalopoda

26. Class Cephalopoda Cephalopods (squid, octopus, cuttlefish)
Most active and intelligent
Head is attached to their foot
Tentacles with sucking disk for capturing prey
Most have small internal shells or no shells at all
Jet propulsion movement and color change (chromatophore).
Nautiluses: the only cephalopods with shell
Cuttlefish: small shell inside of their bodies
Squid: internal shell, which is called the “pen”
Octopi: no shells at all

27. Giant Squid Architeuthis Largest invertebrates
Largest eyes in the Animal Kingdom
Humboldt Squid -

28. 46 feet long
Predator: Sperm whale
                                 

29. Leech