FLATWORMSFLATWORMS

Unit 11: InvertebratesUnit 11: Invertebrates

IN 257 & 259IN 257 & 259

Phylum PlatyhelminthesPhylum Platyhelminthes

Platyhelminthes: “flat” Platyhelminthes: “flat” wormworm

Only one body opening Only one body opening (mouth)(mouth)

Very simple nervous and Very simple nervous and muscular systemsmuscular systems

May be free-living or May be free-living or parasiticparasitic

Ex: planarians, Ex: planarians, tapeworms, flukestapeworms, flukes

PlanariansPlanarians

Free-living flatworm Free-living flatworm

bilateral symmetrybilateral symmetry

Lives in fresh water Lives in fresh water usually under leaves usually under leaves and rocksand rocks

Usually feeds on Usually feeds on dead or slow moving dead or slow moving organisms organisms

Planarian ReproductionPlanarian Reproduction

Reproduction:Reproduction:

SexuallySexually: : hermaphroditeshermaphrodites

AsexuallyAsexually: can : can regenerate missing regenerate missing body parts (called body parts (called fission)fission)

What would happen ????

Detaches its tail end and each half regrows the lost parts

each Planaria gives and receives sperm

Planarians: body structuresPlanarians: body structuresNervous/sensory systemNervous/sensory system: Brain-like structure: Brain-like structure

Nerve cordNerve cord: carries impulses down body: carries impulses down body

EyespotsEyespots: sense light and dark: sense light and dark

Sensory pitsSensory pits: line sides of head to aid in : line sides of head to aid in movement and sensing surroundingsmovement and sensing surroundings

Flame CellsFlame Cells: remove excess water and : remove excess water and nitrogenous wastesnitrogenous wastes

Planarians: body structuresPlanarians: body structuresDigestive/excretory systemDigestive/excretory system

Mouth: located in center of Mouth: located in center of ventral sideventral side

Pharynx: tube like Pharynx: tube like structure which extends structure which extends from mouth during feeding; from mouth during feeding; acts like a straw sucking acts like a straw sucking up food and carrying it to up food and carrying it to bodybody

Food enters mouth and Food enters mouth and solid wastes exit mouthsolid wastes exit mouth

eyespot

ganglion

Gastrovascular cavity

Mouth pharynx

Flame cells

ganglion

Nerve cord

LABEL YOUR PLANARIAN!!!

TapewormsTapeworms

Parasitic flatworm Parasitic flatworm

lives in the intestines lives in the intestines of vertebratesof vertebrates

Can grow up to 10 Can grow up to 10 meters in lengthmeters in length

Sexual reproduction: Sexual reproduction: hermaphroditeshermaphrodites

Tapeworm structuresTapeworm structures

hooks and suckers to hooks and suckers to aid in attachment to aid in attachment to intestineintestine

ProglottidsProglottids: individual : individual segments of wormsegments of worm Each one is detachableEach one is detachable Each proglottid may Each proglottid may

contain up to 100,000 contain up to 100,000 eggs which fall off when eggs which fall off when fullfull

When released, they exit When released, they exit with the host’s wasteswith the host’s wastes

Tapeworm life cycleTapeworm life cycleEggs hatch in intestines of Eggs hatch in intestines of intermediate host (pig or cow)intermediate host (pig or cow)

Young worms burrow out of Young worms burrow out of intestine into pig’s muscle tissue intestine into pig’s muscle tissue forming cystsforming cysts

Secondary host (man) eats Secondary host (man) eats undercooked/raw meat undercooked/raw meat containing worm larvae cystscontaining worm larvae cysts

Larvae hatch and mature in Larvae hatch and mature in intestinesintestines

Attach to intestines, soak up Attach to intestines, soak up digested food of hostdigested food of host

May enter bloodstream and May enter bloodstream and infect other tissues infect other tissues

FlukesFlukes Parasitic flatworm Parasitic flatworm

living in digestive living in digestive system or liver of hostsystem or liver of host

Feeds on body cells, Feeds on body cells, blood and bodily blood and bodily fluidsfluids

Two types: Liver and Two types: Liver and blood flukesblood flukes

Liver flukesLiver flukes: : lodge in liver ducts of lodge in liver ducts of

host causing liver host causing liver damage or failuredamage or failure

FlukesFlukesBlood flukeBlood fluke life cycle: life cycle:

Eggs are released in water Eggs are released in water from wastes of infected hostfrom wastes of infected host

Hatch in to swimming larvae Hatch in to swimming larvae in waterin water

Larvae enter a host (like a Larvae enter a host (like a snail) where they develop & snail) where they develop & maturemature

Enter water again and bore Enter water again and bore into skin of new host (man)into skin of new host (man)

From the blood stream they From the blood stream they bore into intestines where bore into intestines where they attach and feed on they attach and feed on bloodblood