1. 1 Dissection of the Clam Venus mercenaria copyright cmassengale

2. 2

3. 3 Taxonomy of Bivalve Mollusks Kingdom Phylum Class Genus Species Animalia Mollusca Bivalvia Venus mercenaria copyright cmassengale

4. 4 Bivalve Mollusks Soft bodies invertebrates Have a muscular foot that can be extended for movement Two part, hinged shell Complete, one-way digestive tract with a mouth & anus Separate sexes copyright cmassengale

5. 5 Bivalve Mollusks No eyes or distinct head Have siphons to circulate water through their bodies Filter feed on plankton Mussels are large and have a flat, more oblong shell shape, while freshwater clams are smaller (3/4 inch) and typically more round copyright cmassengale

6. 6 Indirect Development Goes through a free- swimming, larval stage called the trochophore Adults move slowly by their extendable foot copyright cmassengale

7. 7 Bivalve Mollusks Protostomes – blastopore becomes the mouth Have a fully lined body or mantle cavity Body organs called visceral mass protected by mantle which secretes the shell Open circulation Most are sessile or sedentary Includes clams, oysters, scallops, & mussels copyright cmassengale

8. 8 Bivalves

9. 9

10. 10 External Anatomy copyright cmassengale

11. 11 Bivalve Shell Umbo is the raised, oldest part of the shell and is used to find surfaces Dorsal Ventral Anterior Posterior UMBO copyright cmassengale

12. 12 Bivalve Shell Shell show regular spacing of external growth rings on shells and their progressive crowding as the animals grow older Growth Rings copyright cmassengale

13. 13 Bivalve Shell Bivalves have an incurrent and excurrent siphon to bring in water containing food & O 2 and for excess water & wastes to leave Siphons copyright cmassengale

14. 14copyright cmassengale

15. 15 The hinge ligament holds the two halves of the shell together Bivalve Shell copyright cmassengale

16. 16 Internal Anatomy copyright cmassengale

17. 17 Scissor tips or a screwdriver & can be used to open the shell copyright cmassengale

18. 18 Adductor Muscles Strong adductor muscles help open & close the valves and must be cut to examine the interior of the clam copyright cmassengale

19. 19copyright cmassengale

20. 20 Inside Shell Lining The inside of the shell is pearly and smooth to protect the body Oysters coat irritants with a substance called “mother of pearl” copyright cmassengale

21. 21copyright cmassengale

22. 22 Teeth located on the dorsal edge of the shell lock to keep shells from sliding copyright cmassengale

23. 23 The mantle makes a CaCO 3 (limestone) shell copyright cmassengale

24. 24 Mantle cavity Gills hang outside visceral mass (body) in the mantle cavity & remove O 2 as H 2 O flows over them Gills copyright cmassengale

25. 25copyright cmassengale

26. 26copyright cmassengale

27. 27copyright cmassengale

28. 28 Water Flow Incurrent siphons aid in bringing in water with food and oxygen Cilia direct water into the gills, while labial palps direct water into the mouth Cilia on the gills pulls in water move food toward the mouth copyright cmassengale

29. 29 VISCERAL MASS - contains respiratory, digestive, & reproductive systems copyright cmassengale

30. 30 HEART & PERICARDIAL CAVITY copyright cmassengale

31. 31 Nervous System Consists of 3 pairs of ganglia (brain) Has 2 pairs of nerve cords extending from this copyright cmassengale

32. 32 Nitrogen waste from kidney Digestive waste from anus Sperm or egg (if external fertilization) Larva (if internal fertilization) Released into Mantle Cavity to be removed by excurrent Siphon: copyright cmassengale

33. 33copyright cmassengale

34. 34copyright cmassengale