1 Dissection of the Clam Venus mercenaria Modified from :

2 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 Modified from :

3 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 Modified from :

4 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 Modified from :

5 External Anatomy Modified from :

6 Bivalve Shell Umbo is the raised, oldest part of the shell and is used to find surfaces Dorsal Ventral Anterior Posterior UMBO Modified from :

7 Bivalve Shell Shell show regular spacing of external growth rings on shells and their progressive crowding as the animals grow older Growth Rings Modified from :

8 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 Modified from :

9 The hinge ligament holds the two halves of the shell together Bivalve Shell Modified from :

10 Internal Anatomy Modified from :

11 Adductor Muscles Strong adductor muscles help open & close the valves and must be cut to examine the interior of the clam Modified from :

12 Modified from :

13 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” Modified from :

14 Modified from :

15 Teeth located on the dorsal edge of the shell lock to keep shells from sliding Modified from :

16 The mantle makes a CaCO 3 (limestone) shell Modified from :

17 Mantle cavity Gills hang outside visceral mass (body) in the mantle cavity & remove O 2 as H 2 O flows over them Gills Modified from :

18 Modified from :

19 Modified from :

20 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 Modified from :

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