1. M OLLUSCA Instructor: Almonther I. Alhamedi The Islamic University of Gaza Department of Biology E-mail : mhamedi@iugaza.edu.psmhamedi@iugaza.edu.ps Web page :http://site.iugaza.edu.ps/mhamedihttp://site.iugaza.edu.ps/mhamedi

2. C HARACTERISTICS OF P HYLUM M OLLUSCA 1. Body bilaterally symmetrical (bilateral asymmetry in some); unsegmented; often with definite head 2. Ventral body wall specialized as a muscular foot, variously modified but used chiefly for locomotion 3. Dorsal body wall forms pair of folds called the mantle, which encloses the mantle cavity, is modified into gills or lungs, and secretes the shell (shell absent in some) 4. Surface epithelium usually ciliated and bearing mucous glands and sensory nerve endings 5. Coelom limited mainly to area around heart, and perhaps lumen of gonads and part of kidneys 6. Complex digestive system; rasping organ (radula) usually present; anus usually emptying into mantle cavity

3. C HARACTERISTICS OF P HYLUM M OLLUSCA 7. Open circulatory system (mostly closed in cephalopods) of heart (usually three chambered), blood vessels, and sinuses; respiratory pigments in blood 8. Gaseous exchange by gills, lungs, mantle, or body surface 9. One or two kidneys (metanephridia) opening into the pericardial cavity and usually emptying into the mantle cavity 10. Nervous system of paired cerebral, pleural, pedal, and visceral ganglia, with nerve cords and sub epidermal plexus; ganglia centralized in nerve ring in gastropods and cephalopods 11. Sensory organs of touch, smell, taste, equilibrium, and vision (in some); eyes highly developed in cephalopods

4. CLASS M ONOPLACOPHORA Neopilina, class Monoplacophora. Living specimens range from 3 mm to about 3 cm in length. A, Ventral view. B, Dorsal view.

5. CLASS P OLYPLACOPHORA Anatomy of a chiton

6. 6 C LASS S CAPHOPODA Tooth shells Shell opens on both ends Burrow into mud No gills Mantle for gas exchange Feed on detritus and protozoa

7. C LASS S CAPHOPODA

8. CLASS G ASTROPODA

9. C LASS B IVALVIA

10. 10 C LASS C EPHALOPODA Shell in squid and octopus absent or vestigial Jet propulsion Ink sac Arms and tentacles Marine All predators

11. C LASS C EPHALOPODA