WORMS WORMS

Flatworms: Phylum Flatworms: Phylum PlatyhelminthesPlatyhelminthes

Soft and FlatSoft and Flat Tissues and Internal Organ SystemsTissues and Internal Organ Systems 3 embryonic germ layers (Ecto, 3 embryonic germ layers (Ecto,

Meso, & Endoderm)Meso, & Endoderm) Bilateral symmetryBilateral symmetry CephalizationCephalization AcoelomatesAcoelomates-without coelom (no -without coelom (no

fluid-filled body cavity)fluid-filled body cavity)

FeedingFeeding

Mouth/anusMouth/anus with with pharynxpharynx (muscular tube that (muscular tube that moves food and waste)moves food and waste)

Gastrovascular cavityGastrovascular cavity – digestion/absorption – digestion/absorption ParasitesParasites – simple or no digestive system b/c – simple or no digestive system b/c

feed on blood, tissue fluids, or cell pieces of hostfeed on blood, tissue fluids, or cell pieces of host

•Carnivore

•Scavenger

•Parasitic

Respiration, Circulation, Respiration, Circulation, ExcretionExcretion

Diffusion (transport ODiffusion (transport O22 and and nutrients) through body wallsnutrients) through body walls

Flame cellsFlame cells – remove excess water – remove excess water and wasteand waste Connected to pores in the skinConnected to pores in the skin

Response Response

GangliaGanglia – controls N.S. (nerve cell – controls N.S. (nerve cell cluster)cluster)

EyespotEyespot – detects light changes – detects light changes Some have specialized cells to detect Some have specialized cells to detect

chemicals, food, etc.chemicals, food, etc.

MovementMovement

Cilia on epidermal Cilia on epidermal cells for gliding cells for gliding

Muscle cells for Muscle cells for twisting/turningtwisting/turning

ReproductionReproduction

HermaphroditesHermaphrodites Sexual by 2 worms Sexual by 2 worms

joining, exchanging joining, exchanging sperm, and each sperm, and each lay eggs lay eggs

Internal Internal fertilizationfertilization

Asexual by Asexual by fissionfission (organism splits in (organism splits in 2 and each half 2 and each half grows new parts)grows new parts)

Freshwater flatworms have simple ganglia and nerve cords that run the length of the body. The excretory system consists of a network of tubules connected to flame cells that remove excess water and cell wastes.

Most flatworms are hermaphrodites, having male reproductive organs (testes) and female reproductive organs (ovaries) in the same organism.

Flatworms use a pharynx to suck food into the gastrovascular cavity. Digested food diffuses from the cavity into other cells of the body. Eyespots in somespecies detect light.

Eyespot

Head

Gastrovascularcavity

Ganglia

Nervecords

Excretorysystem

Mouth Pharynx

Ovary

Testes

Excretorytubule

Flame cell

Figure 27–3 The Anatomy of a Flatworm

Classes of Flatworms: Classes of Flatworms: TurbellariansTurbellarians FlukesFlukes TapewormsTapeworms

Class Turbellaria: Class Turbellaria: TurbellariansTurbellarians

Free-livingFree-living Marine or fresh Marine or fresh

waterwater Not ParasiticNot Parasitic

Ex. Pseudobiceros gloriosusTropical free-living flatworm (non-parasitic)

Ex. PlanariaEx. Planaria Cross-eyed; fresh water free-living flatworm Cross-eyed; fresh water free-living flatworm

(non-parasitic)(non-parasitic)

Class Trematoda: FlukesClass Trematoda: Flukes ParasiticParasitic Infect internal organs Infect internal organs

of hostsof hosts Blood flukesBlood flukes – travel – travel

to intestines of hostto intestines of host Some have Multiple Some have Multiple

HostsHosts

Ex. Blood Fluke Ex. Blood Fluke (not free-(not free-

living)living)

Parasite that matures in human blood vessels

Schistosoma mansoni

(has multiple hosts:Snail=intermediate hostHuman=primary host)

Primary host (human)

Intermediate host(snail)

Human

intestine

Adult

fluke

Embryo

Ciliated

larvaTailed

larva

Flukes mature and reproduce sexually in the blood vessels of human intestines. Embryos are released and passed out with feces.

Once in the water, embryos develop into swimming larvae that infect an intermediate host (snail).

After asexualreproduction, newlarvae are releasedfrom the snail into the water. They then infect humans, the primary host, by boring through their skin.

Figure 27-5

Class Cestoda: Class Cestoda: TapewormsTapeworms

ParasiticParasitic Lives in intestinesLives in intestines Long and flatLong and flat ScolexScolex-head with -head with

suckerssuckers or or hookshooks ProglottidsProglottids-body -body

segmentssegments

• Cow/Fish (intermediate host) consumes food or water w/ zygotes.

• Hatch to larvae and burrow into muscles as cysts (protected)

•human eats meat not fully cooked and larvae activated to grow to adult in human intestines.

Roundworms: Phylum Roundworms: Phylum NematodaNematoda

UnsegmentedUnsegmented Most are free-Most are free-

livingliving Digestive tract Digestive tract

with two openings with two openings – mouth and anus– mouth and anus

PseudocoelomPseudocoelom--false body cavityfalse body cavity

FeedingFeeding Most are carnivoresMost are carnivores Use mouth parts and Use mouth parts and

spines to catch foodspines to catch food

Hook Worms

Respiration, Circulation, Respiration, Circulation, ExcretionExcretion

Diffusion through body wallsDiffusion through body walls

Response Response

Simple nervous system Simple nervous system Nerves run body length from Nerves run body length from

Ganglia in head Ganglia in head Simple sense organs to detect Simple sense organs to detect

chemicals from prey or hostschemicals from prey or hosts

MovementMovement

Hydrostatic skeletonHydrostatic skeleton Muscles and fluid in the Muscles and fluid in the

pseudocoelom work together to pseudocoelom work together to produce movementproduce movement

ReproductionReproduction

SexualSexual Internal fertilizationInternal fertilization Separate gendersSeparate genders

Human DiseaseHuman Disease --Parasitic Roundworms--Parasitic Roundworms

Trichinosis-Causing WormsTrichinosis-Causing Worms Filarial WormsFilarial Worms Ascarid WormsAscarid Worms HookwormsHookworms

Trichinella Trichinella Trichinosis Trichinosis Cysts are ingested Cysts are ingested

from eating animal from eating animal muscle tissuemuscle tissue

Females burrow into Females burrow into intestinal wall intestinal wall

Larvae travel to Larvae travel to organs via organs via bloodstream and form bloodstream and form cystscysts

Filarial WormsFilarial Worms

Live in blood and Live in blood and lymph vesselslymph vessels

Transmitted by Transmitted by mosquitoesmosquitoes

Can block the Can block the movement of fluidsmovement of fluids

ElephantiasisElephantiasis

AscarisAscaris

1. Eggs hatch in 1. Eggs hatch in intestinesintestines

2. Larvae burrow into 2. Larvae burrow into bloodstream to lungsbloodstream to lungs

3. Travel to air passages, 3. Travel to air passages, then swallowedthen swallowed

4. Carried to the 4. Carried to the intestines and matureintestines and mature

5. Eggs released via feces5. Eggs released via feces

• Spread by eating improperly washed vegetables (foods)

HookwormsHookworms

¼ of the human population infected with ¼ of the human population infected with hookwormshookworms

Eggs hatch outside body and develop in Eggs hatch outside body and develop in soilsoil

Use sharp toothlike plates and hooks to Use sharp toothlike plates and hooks to burrow into skin and enter bloodstreamburrow into skin and enter bloodstream

Travel to lungs and then intestines Travel to lungs and then intestines Suck blood causing weaknessSuck blood causing weakness Don’t walk barefoot outside!!!Don’t walk barefoot outside!!!

--Segmented worms --Segmented worms with a with a coelomcoelom (body (body cavity) that is lined cavity) that is lined

with mesodermwith mesoderm

Annelids: Phylum Annelida

Feeding and digestionFeeding and digestion

Filter feeders to predatorsFilter feeders to predators Earthworm Earthworm

Full Digestive Tract: mouth Full Digestive Tract: mouth pharynxpharynx esophagusesophagus cropcrop gizzardgizzard intestineintestine anus anus

CropCrop- store food- store food GizzardGizzard- grind food- grind food

CirculationCirculation

Closed system, 2 major blood vesselsClosed system, 2 major blood vessels Dorsal blood vessel: tail Dorsal blood vessel: tail head (pumps head (pumps

like heart)like heart) Ventral blood vessel: head Ventral blood vessel: head tail tail

Respiration and Respiration and ExcretionExcretion

Respiration- Respiration- Skin (moist due to mucus secretion) - Skin (moist due to mucus secretion) -

landland Gills - aquaticGills - aquatic

Excretion- Excretion- Nephridia - filter out fluid/liquid wasteNephridia - filter out fluid/liquid waste Anus – solid wasteAnus – solid waste

Movement-Movement- Hydrostatic skeletonHydrostatic skeleton

Longitudinal muscles – short and fatLongitudinal muscles – short and fat Circular muscles – long and thin Circular muscles – long and thin

SetaeSetae- - brushbrush hair-like projectionshair-like projections

Reproduction-Reproduction- Mostly sexual, some hermaphrodites, Mostly sexual, some hermaphrodites,

some separate sexessome separate sexes ClitellumClitellum-thick band secretes mucus -thick band secretes mucus

ring after 2 worms exchange sperm for ring after 2 worms exchange sperm for fertilizationfertilization

Mucus ring slips off and forms Mucus ring slips off and forms protective cocoonprotective cocoonhatching hatching

Classes of Classes of AnnelidsAnnelids

Class Oligochaeta: Class Oligochaeta: OligochaetesOligochaetes- Earthworms- Earthworms

Few setae on each segment Few setae on each segment Soil or fresh waterSoil or fresh water

Class Hirudinea: LeechesClass Hirudinea: Leeches External parasitesExternal parasites Suck blood and body fluids of host Suck blood and body fluids of host Medicinal Uses Medicinal Uses

Reduces swelling and prevents clottingReduces swelling and prevents clotting

Class Polychaeta: Class Polychaeta: PolychaetesPolychaetes

Sandworms, Sandworms, bloodwormsbloodworms

Marine Marine Paired paddle-like Paired paddle-like

appendages w/ appendages w/ setaesetae

Live in coral reefs, Live in coral reefs, sand, mudsand, mud

What do you think caused this What do you think caused this marking?marking?

Worm?Worm? Bacteria?Bacteria? Virus?Virus? Fungus?Fungus? Hickey?Hickey?

RingwormRingworm

Not caused by a worm!Not caused by a worm! Fungal infection Fungal infection Can occur on any part of bodyCan occur on any part of body Contact with infected people, Contact with infected people,

animals, soil, etc.animals, soil, etc. Medically called Medically called TineaTinea

Earthworm Earthworm DissectionDissection

External ViewExternal View

Internal StructureInternal Structure

PharynxPharynx

Aortic ArchesAortic Arches

Seminal VesicleSeminal Vesicle

Seminal ReceptacleSeminal Receptacle

SeptumSeptum

CropCrop

GizzardGizzard

IntestineIntestine

Ventral Nerve CordVentral Nerve Cord

Dorsal Blood VesselDorsal Blood Vessel