MOLLUSCA STRUCTURE Softbodied coelomates multicellular bilateral symmetry Divided

MOLLUSCA

STRUCTURE Soft-bodied coelomates, multicellular, bilateral symmetry Divided into three parts: • head-foot- muscular organ covered in cilia and rich in mucous cells • visceral mass- it is the body cavity that holds the digestive, excretory, and reproductive organs; includes gonads, the kidney, the heart • mantle- folds arise from dorsal body wall and enclose a cavity between themselves and visceral mass • mantle cavity acts as lung

STRUCTURE Gills- specialized portions of mantle that consist of a system of filament as projections rich in blood vessels open circulatory system except cephalpods nephrida-tubular structures, remove nitrogenous waste outer surface of mantle secretes protective shell

DIVERSITY Second most diverse phylum Over 110, 000 species Phylum: Mollusca Classes Polyplacophora- marine mollusks oval bodies, not segmented Ex: chitons

Gastropods- primarily marine, freshwater and terrestrial mollusks, typically live in hard shell Ex: Snail and slugs

Bivalves- two lateral shells hinged dorsally, no distinct head area Ex: oysters and clams Freshwater clam

Cephalopods- active marine predators, well developed brains, intelligent invertebrates Ex: octopuses and squids BLUE RINGED OCTOPUS

NUTRITION Heterotroph Radula is used for feeding, it’s a rasping, tongue-like organ, chitinous teeth in rows • Gastropods use radula to scrape algae and food materials • Food is taken up by cells lining the digestive glands arising from the stomach, and then is passed into the blood. • • Uniqueness • Mollusks have unique structure because some contain radula.

REPRODUCTION Distinct male and female individual Few bivalves and gastropods are hermaphroditic Cross fertilization most common Aquatic mollusks-external fertilization Male and female release gametes in water and mix fertilization occurs • Gastropods-internal fertilization- adaptation allows gastropods to live on land • • •

ECOLOGICAL SIGNIFICANCE Important source of food for humans Economic significance-pearls are produced in oysters Bivalve mollusks called shipworms burrow through wood submerged in the sea damaging boats, docks, and pilings. • Zebra mussel invaded North American ecosystems it affected aquatic ecosystems. • Snail fever-schistosomiasis • • •

ANNELIDA

STRUCTURE • • • tube within a tube with internal digestive tract, tube runs through mouth to anus suspended within the coelom hydrostatic skeleton-locomotion Segmented, multicelluluar Excretory system- ciliated funnel shaped nephridia Digestive tract- pharynx, esophagus, crop, gizzard, and intestine

STRUCTURE • • • Repeated segments- excretory, locomotor organs repeated each segment Setae- bristles of chitin help anchor worm during locomotion Specialized segments Closed circulatory system Lack gills, lungs

DIVERSITY Phylum: Annelida Classes • Polychaeta-free living, well developed head with specialized sense organs, parapodia ex: clamworms, marine worms, peacock worms

• • Oligochaeta- fewer setae than polychaetes, no parapodia, no head region ex: earthworm

• HIRUDINEA- FLATTENED, REDUCED CONTINUOUS COELOM UNLIKE FROM POLYCHAETES AND OLIGOCHAETES EX: LEECHES

NUTRITION heterotroph Earthworms eat through soil and other organic material by expanding strong pharynx • Gizzard grinds organic material • •

REPRODUCTION polychaetes lack gonads, produce gametes directly from germ cells in lining of coelom or in septa • external fertilization in water • Earthworms and leeches are hermaphroditic • Leeches- cross fertilization, unable to self fertilize • Uniqueness • Earthworms are hermaphroditic(male and female)

ECOLOGICAL SIGNIFICANCE • • • Earthworms aerate and enrich the soil Leeches are used to remove excess blood after certain surgeries after they remove excess blood new capillaries form and tissues remain healthy Leeches were used hundreds of years in medicine to take blood out of patients whose diseases were mistakenly believed to be caused by excess blood Freshwater leeches live as external parasites and suck their blood Earthworms are a source of food for numerous animals, like birds, rats, and toads Predation: Ex: bird eats worm

REFERENCES (2002). Blue-ringed octopus. (2002). [Web Photo]. Retrieved from http: //www. pbs. org/kcet/shapeoflife/animals/molluscs 1. html Cortes, L. (Photographer). (n. d. ). Common octopus. [Web Photo]. Retrieved from http: //ocean. nationalgeographic. com/ocean/photos/unique-sea-creatures/ Edwards, J. (Photographer). (n. d. ). Retrieved from http: //animals. nationalgeographic. com/animals/invertebrates/earthworm/ Edwards, J. (Photographer). (n. d. ). Common earthworm. [Web Photo]. Retrieved from http: //animals. nationalgeographic. com/animals/invertebrates/earthworm/ (n. d. ). Excretion and osmoregulation in earthworm. [Web Photo]. Retrieved from http: //images. tutorvista. com/content/excretion-and-osmoregulation/earthworm-cross-section. jpeg (1997). Freshwater clam. (1997). [Print Photo]. Retrieved from http: //www. liveaquaria. com/product/prod_display. cfm? c=1075 1642&pcatid=1642 (n. d. ). Information and facts about snails. [Web Photo]. Retrieved from http: //www. snail-world. com/ Onthank, K. (Photographer). (2011). Eyes of rock let chitons see predators. [Web Photo]. Retrieved from http: //m. today. duke. edu/2011/04/chiton. html Raven, P. , & Johnson, G. (2002). Biology. (Sixth ed. , pp. 899 -909). New York: Mc. Graw-Hill. (n. d. ). Retrieved from http: //7 salemanimalkingdom. wikispaces. com/file/view/T 761279 A. gif/33933193/T 761279 A. Skerry, B. (Photographer). (n. d. ). Caribbean reef squid. [Web Photo]. Retrieved from http: //ocean. nationalgeographic. com/ocean/photos/squid/ (n. d. ). The lumbricus rubellus genome project and annelid est database. [Web Photo]. Retrieved from http: //xyala. cap. ed. ac. uk/Lumbribase/images/earthworm 1. jpg gif