FLATWORMS Unit 11: Invertebrates IN 257 & 259

Phylum Platyhelminthes Platyhelminthes: “flat” worm Only one body opening (mouth) Very simple nervous and muscular systems May be free-living or parasitic Ex: planarians, tapeworms, flukes

Planarians Free-living flatworm bilateral symmetry Lives in fresh water usually under leaves and rocks Usually feeds on dead or slow moving organisms

Planarian Reproduction Reproduction: Sexually: hermaphrodites Asexually: can regenerate missing body parts (called fission) What would happen ???? Detaches its tail end and each half regrows the lost parts each Planaria gives and receives sperm

Planarians: body structures Nervous/sensory system: Brain-like structure Nerve cord: carries impulses down body Eyespots: sense light and dark Sensory pits: line sides of head to aid in movement and sensing surroundings Flame Cells: remove excess water and nitrogenous wastes

Planarians: body structures Digestive/excretory system Mouth: located in center of ventral side Pharynx: tube like structure which extends from mouth during feeding; acts like a straw sucking up food and carrying it to body Food enters mouth and solid wastes exit mouth eyespot ganglion Gastrovascular cavity Mouth pharynx Flame cells ganglion Nerve cord LABEL YOUR PLANARIAN!!!

Tapeworms Parasitic flatworm lives in the intestines of vertebrates Can grow up to 10 meters in length Sexual reproduction: hermaphrodites

Tapeworm structures hooks and suckers to aid in attachment to intestine Proglottids: individual segments of worm Each one is detachable Each one is detachable Each proglottid may contain up to 100,000 eggs which fall off when full Each proglottid may contain up to 100,000 eggs which fall off when full When released, they exit with the host’s wastes When released, they exit with the host’s wastes

Tapeworm life cycle Eggs hatch in intestines of intermediate host (pig or cow) Young worms burrow out of intestine into pig’s muscle tissue forming cysts Secondary host (man) eats undercooked/raw meat containing worm larvae cysts Larvae hatch and mature in intestines Attach to intestines, soak up digested food of host May enter bloodstream and infect other tissues

Flukes Parasitic flatworm living in digestive system or liver of host Feeds on body cells, blood and bodily fluids Two types: Liver and blood flukes Liver flukes: lodge in liver ducts of host causing liver damage or failure lodge in liver ducts of host causing liver damage or failure

Flukes Blood fluke life cycle: Eggs are released in water from wastes of infected host Hatch in to swimming larvae in water Larvae enter a host (like a snail) where they develop & mature Enter water again and bore into skin of new host (man) From the blood stream they bore into intestines where they attach and feed on blood