Kingdom Animalia Subkingdom Eumetazoa Bilateria Phylum Mollusca

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Tracy Barber
5 years ago
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1 Kingdom Animalia Subkingdom Eumetazoa Bilateria Phylum Mollusca Professor Andrea Garrison Biology 3A Illustrations 2014 Cengage Learning unless otherwise noted

2 Phylum Mollusca Molluscs (mollis = soft) Chitons, clams, tusk shells, snails, octopods. Mollusca; tusk shell photo BIODIDAC, 2

3 Phylum Mollusca Marine, freshwater, moist terrestrial habitats Free-living Wide range of feeding styles Scrape plant material Filter microscopic organisms Predators Triploblastic Protostomes Bilateral w/cephalization Mollusca 3

4 Phylum Mollusca Trochophore larvae Embryological development results in trochophore May be followed by veliger stage before metamorphosing into adult Mollusca 4

5 Phylum Mollusca Coelomates Coelom reduced to area around heart, gonads 1-2 metanephridia 2 ventral nerve cords w/paired ganglia Most with exoskeleton (shell) secreted from epithelial mantle 3 body regions Head Foot Visceral mass Mollusca 5

6 Phylum Mollusca 3 body regions Head well developed Mouth w/ radula for scraping food or drilling through shell of prey Sensory structures Eyes, tentacles Muscular ventral foot Locomotion May be modified Visceral mass Major organs Mollusca 6

7 Phylum Mollusca Mantle Part of dorsal body wall Encloses visceral mass Secretes shell Usually calcium carbonate Defines separate mantle cavity Houses gills or lung Aquatic species cilia create water currents into mantle cavity Mollusca 7

8 Phylum Mollusca Size requires circulatory system Open circulatory system Blood vessels from heart open into sinuses and bathe tissues directly Sinuses drained by vessels that return blood back to heart Molluscan blood is hemolymph Mollusca 8

9 Molluscan Body Plans Mollusca 9

10 Phylum Mollusca 5 common classes Polyplacophora; chitons Scaphopoda; tusk shells Gastropods; snails Bivalvia; clams, mussels Cephalopoda; octopods, squid, chambered nautiluses Mollusca 10

11 Class Polyplacophora Chitons (poly = many; plax = flat surface) Sedentary Anchors to rocks Dorsal shell divided into 8 plates Allows it to conform to curvature of rocks and get good suction Dioecious Mollusca 11

Class Gastropoda Snails and slugs (gaster = belly; podos = foot) Most abundant class ~40,000 species Herbivores or predators Herbivores scraped algae or plants with radula Predators use radula to

12 Class Gastropoda Snails and slugs (gaster = belly; podos = foot) Most abundant class ~40,000 species Herbivores or predators Herbivores scraped algae or plants with radula Predators use radula to drill through shell of prey or radula modified as harpoon with poison Conus geographicus Mollusca; photo by Kerry Matz, National Institute of General Medical Services 12

13 Class Gastropoda Head with sensory structures Tentacles have chemical and touch receptors Eyes light sensitive (not image forming) Hermaphroditic or dioecious Mollusca 13

14 Class Gastropoda Most with coiled shell Larval torsion (not related to coiled shell) During larval state, visceral mass rotates 180 o so mantle cavity rests right above head Head can withdraw into mantle cavity Foot pulls up behind In marine snails, foot often has operculum to close off shell Mollusca 14

Class Bivalvia Clams, mussels, scallops (bi = two; valva = folding door) Aquatic; most marine Some anchored to rocks Mussels, oysters Some mobile Clams Use foot to

15 Class Bivalvia Clams, mussels, scallops (bi = two; valva = folding door) Aquatic; most marine Some anchored to rocks Mussels, oysters Some mobile Clams Use foot to burrow in sand or mud Tridacna gigas Mollusca; photo by Christoph Specjalski; 15

16 Class Bivalvia Two shells Hinged dorsally w/elastic ligament Ligament holds shell open 1-2 adductor muscles contract to close shell Mantle cavity inside shells Lined by mantle, which secretes shells Two siphons Incurrent siphon brings water into shells and over gills Excurrent siphon removes water and wastes from shell Mollusca 16

17 Class Bivalvia No head No radula Gills w/cilia and mucus Traps food particles and moves them to mouth Palps assist food to mouth Filters bacteria, phytoplankton, detritus Mollusca 17

18 Class Cephalopoda Octopods, squids, chambered nautiluses (kephale = head; podos = foot) Marine Well-developed head Image-forming eyes Brain Very intelligent Shell External nautiluses Internal squid Lacking octopods Mollusca 18

Class Cephalopoda Foot modified as siphon and arms and tentacles with suckers Siphon used for jet propulsion Very fast Arms may be used for movement Mouth

19 Class Cephalopoda Foot modified as siphon and arms and tentacles with suckers Siphon used for jet propulsion Very fast Arms may be used for movement Mouth w/beak in center of arms Radula helps food move to back of esophagus Camouflage Skin color and texture Ink cloud released through siphon Dioecious Mollusca 19

20 Aquatic Respiratory Organs Gills Mollusca 20

21 Terrestrial Respiratory Organs Trachea Lungs Mollusca 21

Phylum Mollusca. Includes snails and slugs, oysters and clams, and octopuses and squids.

Phylum Mollusca. Includes snails and slugs, oysters and clams, and octopuses and squids. Mollusks Phylum Mollusca Includes snails and slugs, oysters and clams, and octopuses and squids. Bivalves Nautilus Characteristics Soft-bodied invertebrate Covered with protective mantle that may or may