Transcript Molluscs
A. Bilateral Symmetry B. Presence of a muscular foot C. Mantle formed by Dorsal Body wall D. True Coelom E. Complex Digestive System F. Gas exchange through gills, lungs, mantle, or body surface G. Simple Excretory system H. Simple nervous system, with true eyes in SOME species I. Simpler forms monoecious, more complex forms dioecious. J. Larval form in all molluscs known as a trochophore “Stomach footed” Molluscs examples: Snails, Slugs, Whelks, Conchs, Cowries A. This is the largest and most successful class of Molluscs B. Shell, if present, is singular, and whorled around a common axis known as a columella. C. Right handed shells are dextral; left handed are sinistral. D. Rasp like Radula used to scrape food. E. Eyes usually positioned on stalks on head. F. Most forms monoecious A. Dextral shell Sinistral shell Cross section showing columella Queen Conch Marine Calliostoma Pulmonate Land Snail Banana Slug Formerly known as Class Pelecypoda The “hatchet-footed” molluscs Examples: Clams, Oysters, Scallops, Mussels, cockles, coquinas A. These organisms all have two shells B. Bivalves are all sedentary filter feeders C. Incurrent siphons bring water in, excurrent siphons bring water out D. Bivalves secrete their shells using nacre, derived from the compounds in the water Examples of incurrent and excurrent siphons Bivalves have two siphons for the exchange of nutrients and oxygen into their shells and bodies. Oyster Giant Clams Scallop The Process of Pearl formation: A . First, a grain of sand or other foreign material gets caught between the shell of the oyster, and the mantle, which is very tender and delicate. B. Second the irritant is surrounded by nacre, or motherof-pearl, to ease the discomfort felt by the sharp edges. C. The oyster continues to secrete nacre until the pearl is formed in a large enough diameter to stop the irritation. D. Naturally formed pearls are very rare to find, hence their value. E. A poor Japanese noodle-maker by the name of Kokichi Mikimoto was the first to force oysters to form pearls, a process known as culturing. Today, Mikimoto pearls are the most widely sold cultured pearls in the world. Tahitian Black Pearls $12,000 Akoya Japanese Pearls $24,000 Golden South Sea Pearls from Indonesia $65,000 “Head-footed Molluscs” examples: octopus, squid, cuttlefish, nautilus A. The MOST ADVANCED of all mollusc classes B. They feed on fishes, other molluscs, crustaceans and worms C. They have a closed circulatory system – very advanced D. Use funnels for rapid locomotion backwards E. Octopi are loners and have 8 arms/tentacles F. Squid are gregarious and have 10 arms/tentacles G. Both secrete an ink-like substance known as sepia to confuse their attackers. H. The largest Octopi reach a length of about 3 meters, the largest squid (Architeuthis) reaches a length of about 60 feet. I. Architeuthis has the largest eyes in the animal kingdom! J. Water movement in the mantle cavity serves three functions: oxygenation, locomotion, and waste and gamete removal. Giant Octopus Chambered Nautilus Cuttlefish Squid Interesting Facts! Phylum Mollusca is the second largest phylum, behind only the Arthropods Most molluscs are found in the ocean Molluscs are important economically for food and for pearls The biggest predator of scallops is sea stars! That’s all Folks!