Molluscan

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1. Molluscan Succes Prepared by: Jerry D. Taay

2. Evolutionary Perspective Octopuses, squid and cuttlefish are some of the invertebrate world’s most adept predators. Predatory lifestyle have result in the evolution of large brains( by invertebrates standards ), complex sensory structures( by any standards ), rapid locomotion, gasping tentacles, and tearing mouthparts. Cephalopods now includes only about 550 species Zoologist do not know why cephalopods have decline so dramatically. Vertebrates may have outcompeted cephalopods because the vertebrates (bony fish) acquired active, predatory lifestyle.

3. What is Molluscan / Mollusc ? Came from the Latin word molluscus mean Soft. They are Triploblastic Consider second largest animal phylum. It includes herbivores, carnivores, filter feeder and parasite. An invertebrates for a large phylum that includes snail, slugs, mussels, and octopuses. They have soft, segmented body and live in aquatic or damp habitat, and most kinds have an external Calcareous Shell . Known as cone shells deliver a painful sting that can be a lethal to human.

4. Body Parts of Mollusc /Mollusk.

5. Characteristics of Phylum Mollusc . Body of two parts Head-Foot and Visceral mass. Mantle that secretes a calcareous shell that covers the visceral mass. Mantle Cavity functions in Excretion, Gas exchange, elimination of digestive waste and release of reproductive products. Bilateral symmetry. Protostome characteristics, including trochophore larvae, spiral cleavage, and schizocoelous coelom formation. Coelom reduce to cavities surrounding the heart, nephridia , and gonads.

6. Open circulatory system in all but on class (Cephalopods). Radula usually present and use in scraping food.

7. The Three main body region of a Mollusc / Mollusk Head-Foot  Is the elongated w/ an anterior head containing the mouth and certain nervous and sensory structure, and an elongated foot, used for attachments and locomotion . Visceral Mass  Contains the organs of digestion, circulation, reproduction, and excretion and is positioned dorsal to the head-foot. It includes mantle that cover the visceral mass and may secrete a shell.

8. Mantle  Usually attaches to the visceral mass, enfolds most of the body, and may secrete a shell that overlies the mantle.

9. Three layers of Shell Outer layer  outer margin that secrete protein called Periostracum ( is a thin organic coating or “skin” w/c is the outermost layer of the shell of many shelled animals).

10. Middle Layer  is the thickest of the three layer and consist of calcium carbonate mixed with organic materials called Prismatic Layer ( producing tissues and a screen and consisting of calcite or aragonite).

11. Inner Layer  forms a thin sheets of calcium carbonate altering with organic matter called Nacreous Layer ( also known as Mother of Pearl, is an organic- inorgani ccomposite material produce by some mollusks as an inner shell layer; it is also what makes up the outer coating of the pearl). Inner layer

12. Classification of Mollusca Class Gastropods ( G. gastro, stomach and podos , foot ).The large stand most divers of the mollusc classes and i t includes the snails, limpers and slugs, conch, whelks and nudibrach . Usually found on marine habitats and they are herbivores. They have an elongated, flattened foot and a one-piece coiled shell that protects the visceral mass

13. Gastropods Land snail

14. Land snail Such as Helix aspersa They are Hermaphroditic They have three obvious division of the body: 1.Head  a flat long 2. Muscular foot 3. Visceral mass surrounded by shell and provide protection from the predator and prevent desiccation (drying out).

15. Nudibranch Comes from the L. nudus , naked and brankhia , gills. Aquatic Gastropods that have a gill in their mantle cavity richly supplied with blood vessels, functions as a lungs when air is moved in and out through respiratory pores. Group of soft bodied, marine gastropods mollusks w/c shed their shell after their larval stage

16. Nudibranch

17. Limpets Often found living on hard surface in the intertidal zone. Can found on in the places rich in algae on most rocky shores . They are very hardy species and are even found on the stormiest shore all year round

18. Limpet Structure

19. Whelks Is the common name that is applied to a various kinds of sea snail many of which have historically been used, or are still used, by humans for food. They also known as welkor evenwilks . The word originated from the from the Proto-Germanic root “ weluka ”, meaning toturn or revolve .

20. Whelks

21. Conch A tropical marine mollusks with a spiral shell that may bear long projection and have a flared lip. They also called Concha Is a common name that is applied to a number medium to a large-sized sea snail or other shells.

22. Conch

23. Torsion One of the most significant modifition of the molluscan body forms in gastropods occurs early in development. Is a 180, counter clockwise twisting of the visceral mass, mantle, and mantle cavity. Torsion portions the gills, anus, and openings from the excretory and reproductive system just behind the head and nerve cords, and twists the digestive tract into a U shape. It is the action of being twisting or the state of being twisted, especially of one of an object relative to the another.

24. Torsion Before Torsion After Torsion

25. Than You for Your Listening A GROUP REPORT IN ZOOLOGY OF: Jerry Deleon Taay Bachelor of Secondary Education major in Biological Science.

26. EMA EMITS COLLEGE PHILIPPINES Ryan Florencondia ( Zoology Instructor)