Platyhelminthes-3

7/27/2019 Platyhelminthes-3

1/18

Ch. 10,11- Phylums

Platyhelminthes and Nematoda

Flatworms and Roundworms


2/18

Phylum Platyhelminthes

Largest group of acoelomate (no body cavity)worms

Flatworms with middle tissue layer- mesoderm

Tissues organized into organs

Bilaterally symmetrical and flat

Cells lie close to exterior enabling efficient

diffusion of oxygen and carbon dioxide Highly branched gastrovascular cavity runs closeto all tissues giving cells ready access to food

No respiratory or circulatory systems


3/18

Phylum Platyhelmithes

Flatworms

Liver Flukes,Planaria andtapeworms

Marine flatworms

Characteristics:

Ribbon-like bodies

Bilateral symmetry

Branched digestive system No skeleton

Asexual (fission); Hermaphrodites (sexual)

Free movement

Skin breathing


4/18


Class Turbellaria

Most free-living; marine

Dugesia- Freshwater

planarians Digestion- Nutrients

absorbed by intestinal wall

and waste goes out through

mouth

Muscular pharynx comesout of central mouth to

feed

-- Reproduction- Mostlyasexual by attaching

posterior end to stationaryobject and pulling into two

Hermaphrodites canreproduce sexually

Nervous system: Brain,two nerve cords, and light-sensitive eye spots

Water balance- Water

continually enters byosmosis

Flame cells with ciliadraw water to the outside


5/18


Marine flatworm


6/18


7/18

Phylum Platyhelminthes Many parasitic

Endoparasite- internal Ectoparasite- external

Class Cestoidea

Subclass Eucestoda- Parasitic

flatworms (tapeworms) Suckers and hooks attach to walls ofintestines and food absorbed fromhosts intestines directly through thetapeworms skin

String of rectangular body sections

(proglottids) Each proglottid is a reproductive

unit

Added continually through life

May grow up to 12 m (40 ft.) long

Most occur in vertebrates

Dozen types in humans Taenia saginata- Beef

tapeworm

Live in cow muscles in

cysts

High temp. kills larvae Subclass Cestodaria

Body not subdidvided into

proglottids

Larvae in crustaceans; adults

in fish


8/18

Phylum Platyhelmithes


9/18


Largest flatworm class,Trematoda

Parasitic worms called flukes

Endoparasites or ectoparasites Subclass Aspidogastrea

(Aspidobothrea)- Endoparasite ofmollusks

Subclass Digenea- Endoparasites ofvertebrates

Tegument- thick protectivecovering prevents them from being

digested Take nourishment directly from

hosts

Use suckers to attach and themuscular pharynx to suck

nourishment from hosts bodyfluids

Complex life cycles involvemore than one host

Ex: Schistosoma-Responsible forschistosomiasis

From contaminated water Larvae bore into host skin

into blood vessels ofintestines

Block vessels causing

bleeding and damage to liver Snail is intermediate host

Class Monogenea-Monogenetic flukes

One life cycle in one host

Mostly ectoparasites on

vertebrates


10/18


Liver fluke


11/18

Phylum Nematoda

Roundworms- have a

pseudocoelem (body

cavity between endoderm

& mesoderm) Fluid movement serves as

circulatory and gas

exchange system

Fluid also distributes

nutrients to cells fromdigestive system

Long, cylindrical bodies

Majority microscopic andfree-living

One-way digestivesystem

Thick, flexible epidermisprotects and gives shape

Layer of muscle

underneath pulls atepidermis and

pseudocoelem for whip-like movement


12/18

Phylum Nematoda

Roundworms

Ascaris, Trichinella andhookworms

Characteristics:

Flattened bodies Bilateral symmetry

Many are parasites

Fluid-filled body cavity called a pseudocoelem

Digestive tube

No skeleton

Sexual reproduction (Internal fertilization)

Sperm is amoeboid

Free movement

Skin breathing


13/18

Phylum Nematoda

Class Secernentea (Phasmidea)- Phasmids (sensorystructures) in tail

Ascaris, Enterobius, Rhabditis, Turbutrix, Necator,

and Wuchereria

Class Adenophorea (Aphasmidia)- No phasmidsDioctophyme, Trichinella, Trichuris

50 species are parasitic

Plant parasites feed on living plant cells in all parts of

plant, causing wilting and withering

14 species affect humans

Ex:Enterobius (pinworms),Ascaris lumbricoides,

Trichinella spiralis, Necator(hookworms)


14/18

Phylum Nematoda

Trichinella infects pigs

and causes trichinosis

(serious disease caused by

eating undercooked pork) Necatorlive in warm,

moist soils of the tropics

Hookworm larvae enter

bloodstream through soles

of feet
http://rds.yahoo.com/_ylt=A9ibyiEZdEdFWVAAwXaJzbkF;_ylu=X3oDMTBjb3ZrYjNkBHBvcwM0BHNlYwNzcg--/SIG=1g9fdo55h/EXP=1162397081/**http%3a//images.search.yahoo.com/search/images/view%3fback=http%253A%252F%252Fimages.search.yahoo.com%252Fsearch%252Fimages%253Fp%253Dtrichinella%2526ei%253DUTF-8%2526fr%253Dyfp-t-501%2526x%253Dwrt%26w=1650%26h=1100%26imgurl=www.mef.hr%252FPatologija%252Fch_9c%252Fc9c_trichinella_cycle.gif%26rurl=http%253A%252F%252Fwww.mef.hr%252FPatologija%252Fch_9c%253FC%253DM%25253BO%253DA%26size=170.8kB%26name=c9c_trichinella_cycle.gif%26p=trichinella%26type=gif%26no=4%26tt=892%26oid=597373e467e12496%26ei=UTF-8http://rds.yahoo.com/_ylt=A9gnMicMX0dFhAMB.7eJzbkF;_ylu=X3oDMTBjMHZkMjZyBHBvcwMxBHNlYwNzcg--/SIG=1hita34rg/EXP=1162391692/**http%3a//images.search.yahoo.com/search/images/view%3fback=http%253A%252F%252Fimages.search.yahoo.com%252Fsearch%252Fimages%253Fp%253Dnecator%2526ei%253DUTF-8%2526fr%253Dyfp-t-501%2526x%253Dwrt%26w=640%26h=512%26imgurl=workforce.cup.edu%252FBuckelew%252Fimages%252FNecator%252520filariform%2525202.jpg%26rurl=http%253A%252F%252Fworkforce.cup.edu%252FBuckelew%252FNecator%252520americanus%252520filariform%252520larva.htm%26size=49.6kB%26name=Necator%2bfilariform%2b2.jpg%26p=necator%26type=jpeg%26no=1%26tt=349%26oid=5a98063c313084a2%26ei=UTF-8


15/18

Phylum Nematoda

Ascaris

Carried in human waste

After ingestion, eggs hatchinto larvae in intestines

Larvae bore through bloodvessels, enter blood streamand then lungs (causesrespiratory distress)

Larvae may entergallbladder or pancreascausing blockages

Return to intestines tomature and mate

May grow up to 1 ft. inlength
http://rds.yahoo.com/_ylt=A9gnMiTvXUdFzVcAaP.JzbkF;_ylu=X3oDMTBjYzZubXM2BHBvcwM4BHNlYwNzcg--/SIG=1h2k1rj0j/EXP=1162391407/**http%3a//images.search.yahoo.com/search/images/view%3fback=http%253A%252F%252Fimages.search.yahoo.com%252Fsearch%252Fimages%253Fp%253Dascaris%2526fr%253Dyfp-t-501%2526toggle%253D1%2526cop%253Dmss%2526ei%253DUTF-8%26w=504%26h=378%26imgurl=www.selu.edu%252FAcademics%252FFaculty%252Fwbond%252Fnematodes%252FAscaris.jpg%26rurl=http%253A%252F%252Fwww.selu.edu%252FAcademics%252FFaculty%252Fwbond%252Fnematodes%252Fpig.html%26size=206.5kB%26name=Ascaris.jpg%26p=ascaris%26type=jpeg%26no=8%26tt=2,239%26oid=74233dca1c783e6a%26ei=UTF-8


16/18

Phylum Nematoda Ascaris

Trichinella


17/18

Trichinosis

Trichinella spiralis isfound in pork

Trichinosis is a diseasecaused by the Trichinellaworm.

Eggs hatch in the hosts gut

Symptoms:

Diarrhea

Fever

Muscle pain

Death


18/18

Common Parasitic

Roundworms Hookworms attach to

the inside of thedigestive tract

Often found in pets

Pinworms- most common

Heartworms- transmitted to

dogs by mosquitos

Filarial worms- live in blood

where they block blood

vessels or lymph vessels

causing severe swelling

(Elephantitis)

Guinea worm- Ingested withcontaminated water

Cause dracunculiasis

Only found when exiting skin

Found in Africa, India andPakistan

Documents

Platyhelminthes-3