FLAT WORMSFLAT WORMS

Phylum PlatyhelminthesPhylum Platyhelminthes Simple animals with soft leaflike or Simple animals with soft leaflike or

ribbonlike bodies, and includes ribbonlike bodies, and includes flatwormsflatworms, , flukesflukes, and , and tapewormstapeworms

Around Around 20,00020,000 species species Body is unsegmentedBody is unsegmented Bilaterally symmetricalBilaterally symmetrical Called “flatworms” because bodies Called “flatworms” because bodies

are flattened are flattened dorso-ventrallydorso-ventrally

Phylum PlatyhelminthesPhylum Platyhelminthes AcoelomatesAcoelomates-solid bodies without a lined -solid bodies without a lined

body cavity; internal organs lie in a loose body cavity; internal organs lie in a loose tissue called tissue called parenchymaparenchyma

3 body layers3 body layers: ectoderm, mesoderm, : ectoderm, mesoderm, endodermendoderm

Show Show cephalizationcephalization (concentration of (concentration of sensory organs at anterior or head end)sensory organs at anterior or head end)

No circulatory system; body cells No circulatory system; body cells exchange oxygen & carbon dioxide exchange oxygen & carbon dioxide directly with environment by directly with environment by diffusiondiffusion

Phylum PlatyhelminthesPhylum Platyhelminthes Single opening into gastrovascular Single opening into gastrovascular

cavity: cavity: two-way digestive tracttwo-way digestive tract In some a In some a tubular pharynxtubular pharynx can be can be

projectedprojected Mouth located at the front, ventral endMouth located at the front, ventral end Water balance is maintained by Water balance is maintained by

excretory tubules (excretory tubules (protonephridiaprotonephridia) ) equipped with flame cellsequipped with flame cells

Phylum PlatyhelminthesPhylum Platyhelminthes Nervous system: Nervous system: brain and nerve cordsbrain and nerve cords

extending along the bodyextending along the body Circular, longitudinal, and other muscle Circular, longitudinal, and other muscle

fibers enable turning, twisting, and fibers enable turning, twisting, and folding of the bodyfolding of the body

Free-living flatworms move by means of Free-living flatworms move by means of a a ciliated epidermisciliated epidermis and undulations of and undulations of the bodythe body

Parasitic flatworms have thick cell layer Parasitic flatworms have thick cell layer called called tegumenttegument covered by a nonliving covered by a nonliving cuticlecuticle covering their bodies as covering their bodies as protection inside hostsprotection inside hosts

Phylum PlatyhelminthesPhylum Platyhelminthes Mostly hermaphroditesMostly hermaphrodites Sperm and egg are exchanged during Sperm and egg are exchanged during

mutual copulationmutual copulation; internal fertilization; internal fertilization Asexual reproduction by Asexual reproduction by fragmentation fragmentation

and regenerationand regeneration Parasitic species have complex life cycles Parasitic species have complex life cycles

- with several larval stages often with two - with several larval stages often with two or more different hostsor more different hosts

ClassificationClassification Class TurbellariaClass Turbellaria

DugesiaDugesia (planarian)(planarian)

Class Trematoda Class Trematoda (flukes)(flukes) SchistosomaSchistosoma

Class Cestoda Class Cestoda (tapeworms)(tapeworms)

Class Turbellaria Class Turbellaria (Planaria)(Planaria) Most are marine but include Most are marine but include

freshwater planarian (freshwater planarian (DugesiaDugesia)) Spade-shaped anterior end with Spade-shaped anterior end with

light-sensitive light-sensitive eyespotseyespots 2 clusters of nerve cells (2 clusters of nerve cells (gangliaganglia) to ) to

form a simple brain and a nerve netform a simple brain and a nerve net Capable of simple learningCapable of simple learning

Class Turbellaria Class Turbellaria (Planaria)(Planaria)

Move by Move by ciliacilia Feed by Feed by scavengingscavenging or protozoans or protozoans Mouth located at the end of Mouth located at the end of

muscular tube called the muscular tube called the pharynxpharynx which is extended when feedingwhich is extended when feeding

Flame cellsFlame cells help remove wastes to help remove wastes to excretory poresexcretory pores

Class Turbellaria Class Turbellaria (Planaria)(Planaria)

Hermaphrodites that cross-fertilize Hermaphrodites that cross-fertilize eggs; deposited into a capsule until eggs; deposited into a capsule until hatching in 2-3 weekshatching in 2-3 weeks

Reproduce asexually by Reproduce asexually by fragmentationfragmentation

Class Turbellaria Class Turbellaria (Planaria)(Planaria)

Pharynx

Mouth

Gastrovascular Cavity

Nerve Cords

EyespotsBrain

Class Trematoda (Flukes)Class Trematoda (Flukes)

Includes parasitic flukesIncludes parasitic flukes Most around 1 cm long and oval Most around 1 cm long and oval

shapedshaped Require a Require a hosthost to live to live Have Have oral and ventral suckersoral and ventral suckers to cling to cling

to host & suck blood & body fluidsto host & suck blood & body fluids EndoparasitesEndoparasites: live inside a host: live inside a host EctoparasitesEctoparasites: live on outside of host: live on outside of host

Class Trematoda (Flukes)Class Trematoda (Flukes)

Covered in tough, unciliated Covered in tough, unciliated tegumenttegument

Nervous & excretory systems like Nervous & excretory systems like turbellariansturbellarians

HermaphroditesHermaphrodites Long, coiled uterus stores & releases Long, coiled uterus stores & releases

10,000+ eggs10,000+ eggs Eggs released through Eggs released through genital poregenital pore & &

develop into larvadevelop into larva

Class Trematoda (Flukes)Class Trematoda (Flukes)Life cycle of sheep liver fluke (Life cycle of sheep liver fluke (Fasciola Fasciola

hepaticahepatica):):1.1. Adult liver flukes live in sheep Adult liver flukes live in sheep liver & gall liver & gall

bladderbladder where they mate & form eggs where they mate & form eggs

2.2. Eggs enter intestines, pass out with feces, & Eggs enter intestines, pass out with feces, & hatch in waterhatch in water

3.3. Larva enter Larva enter snailssnails, asexually multiply, then , asexually multiply, then leave snail & form cystsleave snail & form cysts

4.4. CystsCysts (dormant larva with hard, protective (dormant larva with hard, protective covering) clings to grasscovering) clings to grass

5.5. Sheep ingest cysts when they eat grassSheep ingest cysts when they eat grass

6.6. Cysts hatch in Cysts hatch in digestive tractdigestive tract & bore through & bore through intestines into intestines into bloodstreambloodstream

7.7. Mature and reproduce in the liverMature and reproduce in the liver

Class Trematoda (Flukes)Class Trematoda (Flukes) SchistosomiasisSchistosomiasis::

disease caused by disease caused by parasitic blood parasitic blood flukes flukes ((Schistosoma)Schistosoma); ; infects people in infects people in Asia, Africa, and Asia, Africa, and South America South America causing intestinal causing intestinal bleeding and bleeding and tissue decay that tissue decay that can result in deathcan result in death

Class Cestoda Class Cestoda (Tapeworms)(Tapeworms) Adapted for Adapted for parasitic lifeparasitic life

Tough outer Tough outer tegument prevents tegument prevents being digested by being digested by hosthost

ScolexScolex: anterior : anterior end, contains end, contains hooks & suckers hooks & suckers for attachment to for attachment to intestine of hostintestine of host

Class Cestoda Class Cestoda (Tapeworms)(Tapeworms)

Long, ribbon-like bodies up to Long, ribbon-like bodies up to 12 m12 m in lengthin length

Nervous system extends length of Nervous system extends length of body but body but lacks sense organslacks sense organs

Lacks mouth and digestive tract; Lacks mouth and digestive tract; absorbs digested nutrients from absorbs digested nutrients from hosthost

Grows by making body segments Grows by making body segments called called proglottidsproglottids

Class Cestoda Class Cestoda (Tapeworms)(Tapeworms)

Each proglottid produces eggs & Each proglottid produces eggs & sperm that cross-fertilize with other sperm that cross-fertilize with other segments & also self-fertilize segments & also self-fertilize (hermaphrodites)(hermaphrodites)

Oldest, mature proglottids Oldest, mature proglottids containing eggs at posterior end; containing eggs at posterior end; break off & pass out with fecesbreak off & pass out with feces

Class Cestoda Class Cestoda (Tapeworms)(Tapeworms) Life cycle of beef tapewormLife cycle of beef tapeworm::

1.1. Cattle eat grass with Cattle eat grass with proglottids containing proglottids containing fertilized eggsfertilized eggs

2.2. Eggs hatch into larva & Eggs hatch into larva & bore through cow’s bore through cow’s intestine into bloodstreamintestine into bloodstream

3.3. Larva burrow into cow’s Larva burrow into cow’s muscle & form cystsmuscle & form cysts

4.4. Humans eat beef (muscle) Humans eat beef (muscle) & cysts travels to & cysts travels to intestinesintestines

5.5. Cyst breaks open & adult Cyst breaks open & adult beef tapeworm formsbeef tapeworm forms