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Phylum: Mollusca

Phylum: Mollusca. Mollusca Overview. General Characteristics. 50,000 or more species of molluscs. They share 3 major sets of characteristics: Body enclosed by a blanket-like mantle that secretes a shell made of calcium or some other stiff structure.

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Phylum: Mollusca

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  1. Phylum: Mollusca

  2. Mollusca Overview

  3. General Characteristics • 50,000 or more species of molluscs. • They share 3 major sets of characteristics: • Body enclosed by a blanket-like mantle that secretes a shell made of calcium or some other stiff structure. • A mantle cavity between the mantle and the internal organs; the anus, reproductive, and excretory ducts open into the mantle cavity. • A ventral, muscular foot that is highly modified among the various groups of molluscs.

  4. Phylum -Mollusca • Three main parts of a Mollusca • Visceral mass – Location of Organs • Mantle tissue makes a calcium carbonate shell (may be reduced) • Foot = muscular structure modified in some way (how determines class)- used for movement • Reduced coelom

  5. Mollusc Body Plan

  6. General Characteristics Cont’d • Free-living, multicellular animals • Invertebrates (lack a backbone) • Unsegmented • Have a true coelom – BODY ADVANCE • Bilateral symmetry • Have a true heart • Simple to complex nervous system • Open circulatory System – BODY ADVANCE

  7. Habitats & Niches • Some mollusc habitats include: • Marine (mostly) • Freshwater (a few) • Land (a few) • Mollusc niches (life-style): • Most live on the ocean bottom and are mostly sedentary • Some are free-swimming (the cephalopods)

  8. The six major mollusc classes • There are seven mollusc classes in total six major ones, of which we will study 3 of them. • Those 3 classes are: • Gastropoda (gastro=body cavity; poda=foot) • Ex. Common garden snail, abalone, turban snail • Bivalvia (bi=two; valvia=valves) • Ex. Clam • Cephalopoda (cephalo=dealing with head; poda=foot) • Ex. Squid, octopus, etc.

  9. Our 3 Classes of Mollusks • Gastropods- The most common type of molluscs….Snails • Bivalves- The body is compressed into a two valved shell….Scallop

  10. Cephalopods – Most agile of the molluscs complex nervous system and a reduction or absence of a shell. Highly Cephalized

  11. Class Gastropoda • Most popular class of molluscs. • Consists of snails and snail-like creatures. • Specific characteristics: • They have a dorsally located shell (often coiled). • They have a well-developed radula. • Visceral mass (organs) is located inside the shell. Their visceral mass is rotated 180 degrees during development. • They are herbivores or predatory (carnivorous). • Habitats include: ocean, lake, river bottoms, coastal shores, and land.

  12. Class: Gastropoda • (gastro=stomach; pod=foot) or Univalvia (one shell) ex: snail, abalone, conch Their bodies are covered by one shell, except for the nudibranch. Most are benthic herbivores, although the dog whelk is carnivorous. Precious Wentletrap Special tongue (radula) with a ribbon of flexible teeth on its surface works like a mini-chain saw. It is used to scrape surfaces for algae or to cut into other shells.

  13. Mollusks have a(n) ________ circulatory system • Open • Closed • They do not have a circulatory system.

  14. The Mollusk has _____ main parts. • 2 • 4 • 3 • 6

  15. Which is NOT a class of Mollusk • Gastropod • Pseudopod • Cephalopod • BiValve

  16. Gastropod tongue is also known as a • Podia • Radula • Mantle • Visceral mass

  17. The only Gastropod which is not covered by a shell is a • Nudibranch • Cuttle fish • Octopus • Conch

  18. Fastest Responders

  19. Class Bivalvia • Specific Characteristics: • They have no head. • They have two shells held together by powerful muscles. • They have a ventrally located foot that sticks out between the two valves. • Habitats include: marine and freshwater. • They tend to burrow into soft mud or sand or attach to rocks or other shells. • Large gills are used for respiration and filter feeding. • Food is trapped by mucus on the gills and moved by cilia. Water enters and exits through siphons.

  20. Class Bivalvia

  21. 2. Class: Pelecypoda or Bivalvia (two footed, also two shells) ex: clams, oysters, scallops They are benthic, planktivores who filter sea water through an incurrent and excurrent pore. Some are sessile (oyster) others swim by opening and closing both shells (scallop).

  22. Class Bivalvia Clams, Oysters, Mussels Byssal Threads On Mussels

  23. Giant Clam

  24. Scallops Oysters

  25. Class Cephalopoda • Contains the largest molluscs. • HIGHLY CEPHALIZED • Specific Characteristics: • May lack a shell (like an octopus) • Shell may be reduced to a stiffening rod (like the squid or nautilus) A Chitionous Pen • The foot is highly modified to form a group of tentacles around the mouth. • They are found in deep and shallow waters along many coasts. • Squids & Nautilus are free-swimming and move very quickly. Octopuses are found among rocks or crawling on the bottom of the ocean. • Complex brain, two lateral eyes, excellent eyesight. • We will dissect a squid. If you are allergic to shellfish then speak up now!!!

  26. Class Cephalopod

  27. Class Cephalopoda

  28. The Amazing Octopi - mouth has a sharp beak for eating worms, fish, etc. - moves by jet-propulsion, mantle fills with water which can be squirted out to propel them backwards - chromatophores in the skin change colors when the animal is alarmed and for camouflage - ink gland is used as a “smoke screen” for a quick escape - eyes have a cornea, lens and retina; excellent vision In the octopus, reproduction is by internal fertilization. During the 30 days until hatching, the female carefully aerate, cleans and watches the eggs - never leaving even to eat. The female usually dies from exhaustion and starvation soon after they hatch.

  29. Chambered Nautilus Cuttlefish

  30. The cuttlefish has an internal shell that is sold to pet stores as a source of calcium for birds. – a cuttle bone The cuttlefish are masters of Color change Cells in their skin called chromatophores cells which are controlled by muscles to create different colors. Cuttlefish

  31. Cephalo means • Head • Foot • Arm • False

  32. The Chitinous pen is found in the • Cuttlefish • Octopus • Squid • Sponges

  33. Fastest Responders

  34. Other Facts The spiraled shell of the chambered nautilus is lined with mother-of-pearl and is perfectly proportioned mathematically. Gas and liquid exchange occurs through the walls and allows the nautilus to regulate buoyancy. Oysters are at the center of the aquaculture industry and are raised for culturing pearls. If an irritant such as a grain of sand gets trapped under the oyster’s mantle, it secretes a coating of a pearl-like material called nacre. Selected oysters are carefully raised to produce pearls of various sizes and colors.

  35. Some even are Bioluminescent Bioluminescence

  36. Any Questions????

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