Coelomates Phylum Mollusca Phylum MOLLUSCA Mollusks Mollusca soft

Phylum: MOLLUSCA (Mollusks) Mollusca – “soft bodied” animals Most are protected by a hard

Common Features of Mollusks Coelomates Protostomes Bilateral Symmetry Triploblastic – All 3 embryonic tissue

Mollusks – Common Structures Head - in most species Foot - muscular for movement

Body Plan of the Mollusk- General Note the following • Foot • Shell •

Body Plan of the Mollusk The Radula The radula is a feeding structure Lined

Phylum Mollusca: Classes Eight classes We will be looking at 4 classes Polyplacophora –

Class: Polyplacophora (Chitons) Marine mollusks Oval body Dorsal surface - covered with eight movable

Class Gastropoda Includes snails and slugs Gastropods - “Belly foot” describes the position of

Class Gastropoda Most of the other organs are located in the spiraled or coneshaped

Class Bivalvia Includes clams, scallops, oysters A two-part shell encloses the body The shell

Bivalve Anatomy Two-part shell Note Hinge Area Adductor muscleskeep shell closed Mantle Secretes the

Bivalve Anatomy Reproduction some hermaphroditic with cross fertilization some have separate sexes Note the

Bivalve Anatomy Filter feeders Water flow Incurrent siphon Across gills Excurrent siphon Food trapped

Bivalve Anatomy Most are sessile or move slowly Scallops can clap their shells together

Pearls Some freshwater mussels and marine oysters produce pearls An irritant (often a parasite)

Class Cephalopoda Includes squids, octopuses, nautiluses Includes the largest invertebrates known the giant squid

Class Cephalopoda Only mollusks with a closed circulatory system supports greater activity Nervous system

Cephalopods are active hunters. They use rapid movements to dart toward their prey which

Squids Fast movements by a squid occur when it contracts its mantle cavity and

Octopuses Most octopuses live on the seafloor. They creep and scurry using their eight

Octopuses They have a well-developed nervous system with a complex brain and well-developed sense

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Coelomates Phylum Mollusca

Phylum: MOLLUSCA (Mollusks) Mollusca – “soft bodied” animals Most are protected by a hard calcium shell 150, 000 species -includes: Chitons Snails and slugs clams, oysters, scallops squid and octopuses Most are marine; some terrestrial

Common Features of Mollusks Coelomates Protostomes Bilateral Symmetry Triploblastic – All 3 embryonic tissue layers Ectoderm Mesoderm Endoderm

Mollusks – Common Structures Head - in most species Foot - muscular for movement Shell - Made of calcium carbonate secreted by the mantle Mantle - skirtlike tissue covering the body Gills For gas exchange Radula (a rasping tonguelike structure)

Body Plan of the Mollusk- General Note the following • Foot • Shell • Mantle • Radula • Visceral Mass contains organs for • Reproduction • Digestion • Excretion • Lack of a “Head”

Body Plan of the Mollusk The Radula The radula is a feeding structure Lined with cutting plates Used for grazing Scraping algae, plants or small animals from surfaces

Phylum Mollusca: Classes Eight classes We will be looking at 4 classes Polyplacophora – the chitons Gastropoda – snails and slugs Bivalvia – clams, oysters, scallops etc. Cephalopodia – squid and octopus

Class: Polyplacophora (Chitons) Marine mollusks Oval body Dorsal surface - covered with eight movable plates Ventral surface- covered by a large adhesive foot. A radula is used to scrape small animals from the rocks along the seashore

Class Gastropoda Includes snails and slugs Gastropods - “Belly foot” describes the position of the large muscular foot underneath the animal when it is crawling. Most of the other organs are located in the spiraled or cone-shaped shell.

Class Gastropoda Most of the other organs are located in the spiraled or coneshaped shell. As the larvae develop, the internal organs undergo a unique twisting, or torsion, that places the anus anteriorly near the mouth.

Class Bivalvia Includes clams, scallops, oysters A two-part shell encloses the body The shell is secreted by the mantle The innermost layer is the pearly nacre. Not highly cephalized Have no recognizable head Large foot is specialized for burrowing

Bivalve Anatomy Two-part shell Note Hinge Area Adductor muscleskeep shell closed Mantle Secretes the shell Muscular Foot Lack of cephalization

Bivalve Anatomy Reproduction some hermaphroditic with cross fertilization some have separate sexes Note the gonads Gills – respiratory organ Open circulatory system

Bivalve Anatomy Filter feeders Water flow Incurrent siphon Across gills Excurrent siphon Food trapped on mucus coated gills Transferred to mouth by the palp Trace the digestive system from mouth to anus

Bivalve Anatomy Most are sessile or move slowly Scallops can clap their shells together to produce a jet of water that propels the animal forward Note the row of eyes

Pearls Some freshwater mussels and marine oysters produce pearls An irritant (often a parasite) is surrounded by layers of nacre secreted by the mantle.

Class Cephalopoda Includes squids, octopuses, nautiluses Includes the largest invertebrates known the giant squid can attain a length of 60 feet. The octopus is probably the most intelligent invertebrate Highly active move by a type of jet propulsion caused by contractions of the mantle Predatory life-style have tentacles and beaklike jaws

Class Cephalopoda Only mollusks with a closed circulatory system supports greater activity Nervous system well developed with a large brain Compound lens eye – resembles the eye of vertebrates – forms images Most intelligent invertebrates Learning and memory are possible.

Cephalopods are active hunters. They use rapid movements to dart toward their prey which they capture with several long tentacles. Squids and octopuses use beaklike jaws to bite their prey and then inject poison to immobilize the victim

Squids Fast movements by a squid occur when it contracts its mantle cavity and fires a stream of water through the excurrent siphon. By pointing the siphon in different directions, the squid can rapidly move in different directions. The foot has been modified into the muscular siphon and parts of the tentacles and head. Most squid are less than 75 cm long, but the giant squid, the largest invertebrate, may reach 17 m (including tentacles) and weigh about 2 tons.

Octopuses Most octopuses live on the seafloor. They creep and scurry using their eight arms in search of crabs and other food. They can quickly change colors to hide from predators or to communicate with each other. Color changes are used to attract mates and warn off competitors.

Octopuses They have a well-developed nervous system with a complex brain and well-developed sense organs. This supports learning and complex behavior. An octopus can learn to solve a maze quicker than the average lab rat. They quickly learn how to escape a tank by manipulating handles or opening locks.

Cephalopods