WORMSWORMS

WORMSWORMS

Over 20,000 wormlike organismsOver 20,000 wormlike organisms Classified into 6-8 different phylumClassified into 6-8 different phylum All have bilateral symmetryAll have bilateral symmetry Bodies have true tissues, organs and Bodies have true tissues, organs and

organ systemsorgan systems Tissues derived from 3 germ layers: ecto, Tissues derived from 3 germ layers: ecto,

meso, and endodermmeso, and endoderm We will be looking at the 3 most important We will be looking at the 3 most important

worm phyla: flatworms, round worms, and worm phyla: flatworms, round worms, and segmented worms. (largest # of species segmented worms. (largest # of species and greatest impact on humans)and greatest impact on humans)

Phylum Platyhelminthes Phylum Platyhelminthes (Flatworms) Characteristics:(Flatworms) Characteristics:

Divided into 3 classes: Divided into 3 classes: turbellariaturbellaria (free (free living flatworms; living flatworms; trematoda trematoda (flukes); and (flukes); and cestodacestoda (tapeworms) (tapeworms)

Within the 3 classes approx. 10,000 speciesWithin the 3 classes approx. 10,000 species Very flat, thin bodyVery flat, thin body Have a headHave a head Bilateral SymmetryBilateral Symmetry Sensory organs in the anterior region Sensory organs in the anterior region

(light/smell): they can detect food and (light/smell): they can detect food and move toward it.move toward it.

Flatworm characteristics Flatworm characteristics cont…cont…

Have a brain, nerve cells (control Have a brain, nerve cells (control center)center)

Most primitive organisms to show Most primitive organisms to show cephalizationcephalization

Classes of FlatwormsClasses of Flatworms#1: Class Turbelaria – (Free #1: Class Turbelaria – (Free

living flatworms)living flatworms) Free living – those that are NOT parasitesFree living – those that are NOT parasites Most common are Most common are planariansplanarians (fresh or salt water (fresh or salt water

organisms) about 1 or 2 cm organisms) about 1 or 2 cm Have a “blind” digestive system: mouth is the Have a “blind” digestive system: mouth is the

only entrance or exit. only entrance or exit. Have a nervous systemHave a nervous system Has two light-sensitive spots that resemble eyes Has two light-sensitive spots that resemble eyes

on it’s head (they sense light and dark)on it’s head (they sense light and dark) Take in excess water by osmosis; and remove Take in excess water by osmosis; and remove

excess water by ciliated flame cellsexcess water by ciliated flame cells Hermaphrodites – each individual produces male Hermaphrodites – each individual produces male

and female gametes (sperm from one worm and female gametes (sperm from one worm fertilizes eggs of another worm)fertilizes eggs of another worm)

Planarians cont…Planarians cont…

Most are carnivorous (eat protists/small Most are carnivorous (eat protists/small animals) which they trap in secretions animals) which they trap in secretions from their mucous glands. from their mucous glands.

They grasp its prey with its mouth and They grasp its prey with its mouth and wrap their body around the preywrap their body around the prey

The pharynx breaks food organisms into The pharynx breaks food organisms into small pieces and pushes them into the gut. small pieces and pushes them into the gut. Food molecules are diffused from gut cells Food molecules are diffused from gut cells to the other body cells. to the other body cells.

Undigested food is expelled through the Undigested food is expelled through the pharynx and the mouth.pharynx and the mouth.

Ability to regenerateAbility to regenerate

Class Trematoda: FlukesClass Trematoda: Flukes

Parasitic flatwormsParasitic flatworms Organs and organ systems similar to Organs and organ systems similar to

planariansplanarians Outer layer has a tough, nonliving material Outer layer has a tough, nonliving material

called a cuticle that protects it from called a cuticle that protects it from digestive enzymes of its host.digestive enzymes of its host.

Have two suckerlike disks; one on the Have two suckerlike disks; one on the ventral surface & one around mouthventral surface & one around mouth

Suckers attach the worm to the host Suckers attach the worm to the host (host’s digestive tract) and it absorbs (host’s digestive tract) and it absorbs digested food from the host’s intestinedigested food from the host’s intestine

Class Cestoda: TapewormsClass Cestoda: Tapeworms

All cestodes (tapeworms) are parasitic flatwormsAll cestodes (tapeworms) are parasitic flatworms Tapeworms are more specialized than flukesTapeworms are more specialized than flukes Body is divided into many sections or proglottids Body is divided into many sections or proglottids

(and it will continue to make more of these (and it will continue to make more of these sections just behind its head)sections just behind its head)

Species vary in length and number of proglottids Species vary in length and number of proglottids – some have thousands– some have thousands

No digestive system (they live in the intestine of No digestive system (they live in the intestine of a hosta host

Several human tapeworms are transmitted by Several human tapeworms are transmitted by infected pork, beef, or wild game that hasn’t been infected pork, beef, or wild game that hasn’t been cookedcooked

http://www.youtube.com/watch?v=txSiApFzaZE

TapewormTapeworm

Phylum Nematoda: Phylum Nematoda: RoundwormsRoundworms

Round tubelike shapeRound tubelike shape Extremely common (10,000 species)Extremely common (10,000 species) Small (less than a few mm in length)Small (less than a few mm in length) Soil and waterSoil and water Most are harmless (except parasitic forms)Most are harmless (except parasitic forms) One way digestive tract (two openings); One way digestive tract (two openings);

food enters the mouth and waste is food enters the mouth and waste is expelled from an anusexpelled from an anus

Have a body cavity that fills with fluid Have a body cavity that fills with fluid giving a round shape. – much like air in a giving a round shape. – much like air in a tire; fluid also circulates material through tire; fluid also circulates material through the bodythe body

Parasitic NematodesParasitic Nematodes

Hookworm is a common roundworm parasite of Hookworm is a common roundworm parasite of humanshumans

Occurs where sanitation is poor and where Occurs where sanitation is poor and where human wastes are used as fertilizer, or where human wastes are used as fertilizer, or where people are commonly barefootpeople are commonly barefoot

Human waste from an infected person contain Human waste from an infected person contain hookworm eggs. Eggs get in soil and develop hookworm eggs. Eggs get in soil and develop into larval worms. Larval worms contact skin and into larval worms. Larval worms contact skin and pierce through and burrow in the body. Larvae is pierce through and burrow in the body. Larvae is carried by the blood to different body parts. Adult carried by the blood to different body parts. Adult worms attach to the intestine wall and feed on worms attach to the intestine wall and feed on blood and tissue.(ex: sheep liver fluke)blood and tissue.(ex: sheep liver fluke)

http

http://www.youtube.com/watch?v=GiHtUFuGgSA&feature=related

HookwormHookworm

Hookworm Info.Hookworm Info.

Affects 1 billion people worldwideAffects 1 billion people worldwideCommonly causes death in children Commonly causes death in children

because it increases their because it increases their susceptibility to other diseases that susceptibility to other diseases that could normally be toleratedcould normally be tolerated

Very little chance of contracting it in Very little chance of contracting it in the US or Canada due to our the US or Canada due to our advances in sanitation and waste advances in sanitation and waste controlcontrol