phylum platyhelminthes l.
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PHYLUM PLATYHELMINTHES. FLAT BODIED WORMS Class Turbellaria (planarians) mostly predatory free living Class Trematoda (internal flukes) only parasitic complex life-cycles Class Cestoda (tapeworms) only parasitic. EXAMPLES. PLANARIA – FREE LIVING – AQUATIC AND TERRESTRIAL

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phylum platyhelminthes

PHYLUM PLATYHELMINTHES

FLAT BODIED WORMS

Class Turbellaria (planarians)

mostly predatory

free living

Class Trematoda (internal flukes)

only parasitic

complex life-cycles

Class Cestoda (tapeworms)

only parasitic

examples
EXAMPLES
  • PLANARIA – FREE LIVING – AQUATIC AND TERRESTRIAL
    • Herbivore, carnivore, scavenger
  • TAPEWORMS – INTESTINAL PARASITE W/ MORE THAN 1 HOST TAENIA
  • FLUKES – INTERNAL PARASITE W/MORE THAN ONE HOST
    • BLOOD FLUKE SCHISTOSOMA
    • LIVER FLUKE FASCIOLA
traits
TRAITS
  • ORGAN LEVEL OF ORGANIZATION
  • BILATERAL SYMMETRY
  • SAC TYPE BODY – 1 OPENING/ no anus
    • GASTROVASCULAR CAVITY IS BRANCHED
  • TRIPLOBLASTIC – 3 GERM/tissue LAYERS
  • CEPHALIZATION – has a head
  • BRAIN WITH 2 NERVE CORDS & TRANSVERSE NERVES
  • SENSE ORGANS – light and chemicals
    • Occeli/eyespots and auricles/ears
traits4
TRAITS
  • ACOELOMATE – no coelom/body cavity
  • DIFFUSION METHODS FOR:
    • GAS EXCHANGE - O2 and CO2
    • WASTE REMOVAL – by FLAME CELLS
    • CIRCULATION of nutrients and waste
    • REMEMBER: DIFFUSION IS A SLOW PROCESS; HI TO LO
slide5

Epidermis/

ECTODERM

gut cavity

Lining of gut =ENDODERM

no body cavity; region between gut and body wall packed with organs within MESODERM tissue

Acoelomate organism

(flatworm)

Body Plan

traits6
TRAITS
  • MUSCLES FOR LOCOMOTION
  • REPRODUCTION
    • ASEXUAL – REGENERATE
    • SEXUAL – HERMAPHRODITES BUT CROSS FERTILIZE
evolutionary milestone
EVOLUTIONARY MILESTONE
  • ORGAN LEVEL OF ORGANIZATION
    • reproductive, excretory, muscular
  • BILATERAL SYMMETRY
  • CEPHALIZATION
    • Anterior and posterior
    • Dorsal and ventral
platyhelminthes taxonomy

Platyhelminthes Taxonomy

Classes of Phylum Platyhelminthes

slide9
--Widely distributed in N. America
  • -- about 200 species
  • --Occur in both lakes and streams
  • -- Stream-dwelling species more differentiated than lake species
  • --Species diversity increases in temperate areas 20 to 60 species per lake

Planaria

Class Turbellaria

slide10

Class Turbellaria

  • Free-living flatworms; mostly marine
  • microscopic to two feet
  • Locomotion in Turbellaria
  • move by means of cilia and mucous
  • 2 layers of muscle; longitudinal and circular
  • Stimulated by nervous system
  • contractions for turning, twisting and folding of the body
slide11

Nutrition in Turbellaria

  • carnivores and predators of other animals or dead remains.
  • muscular pharynx is inserted into prey
  • Secretes digestive enzymes
  • Fragments are pumped into mouth on ventral surface
  • Further digestion in gastrovascular cavity
  • branching increases the surface area for digestion and absorption
  • No anus, only mouth;
  • Undigested food excreted from mouth and pharynx as in cnidaria
  • GVC aids both digestion and circulation – distributes nutrients and oxygen to tissues
sensory nervous

Brain/ganglia

nerve cords

Sensory/nervous
  • Exhibits cephalization
  • Group of nerve tissue (GANGLIA) at anterior
  • Ganglia attached to 2 nerve chords
  • well developed sensory eyespots for light
  • auricles for chemical and mechanical (touch) receptors
slide13

Reproduction in Turbellaria

  • Asexual---
  • By fission or dividing
  • Regeneration of missing parts
  • Sexual-
  • hermaphrodites w/ cross-fertilization
  • Internal fertilization
  • Zygote released to water

testis

penis

genital pore

ovary

oviduct

slide14

EXCRETION IN TURBELLARIA

Excretory pore

Flame cells

Excretory tubules

Excretory

System

pharynx (protruded)

protonephridia

flame cell

nucleus

cilia

  • Cilia of flame cells remove excess water and nitrogen wastes of body
  • Waste moves to tubules
  • Exits out pores in head
  • Needs excretory system as tissues become thicker and more cells present

fluid

filters through membrane folds

opening of tubule at body surface

flame cell

class trematoda the flukes
Class Trematoda – the Flukes

COMMON EXAMPLE

OF COMPLEX

LIFE CYCLE

slide16

Class Trematoda

  • live as parasites
  • protected from digestion by protein coat
  • 2 suckers:
  • 1. Oral sucker attaches to organs of the host
  • 2. Ventral sucker or acetabulumattaches to host tissues
slide17

Types of Hosts

  • Complex life cycles
  • Alternate between sexual and asexual stages
  • Most require at least 2 different kinds of hosts to complete their life cycle
  • 1.Definitive host (primary host)
    • where parasite matures and reproduces (sexually)
    • host in which eggs are released
  • 2. Intermediate host
    • Hosts in which larval stages develop and undergo asexual reproduction
    • Results in an increase in the number of the individuals
slide18

Schistosoma

  • a common blood fluke of SE Asia
  • causes shistosomiasis
  • Definitive host = humans
  • Intermediate host = snails
  • In humans - eggs penetrate and damage intestinal and bladder tissue
  • constant inflammation and eventual deterioration of liver, spleen and other organs

Fluke Life Cycle

slide19

General Life Cycle - Chinese liver fluke, Clonorchis sinensis

  • Adults live in the bile ducts of humans, dogs, and cats
  • There are 2 intermediate hosts: a snail and a fish
  • Eggs are passed out of the definitive host and hatch as ciliated larvae called miracidia
  • The miracidia penetrates a snail molluscan host and becomes a sporocyst
  • They undergo asexual reproduction producing larvae called rediae
  • Rediae often asexually produce more rediae, but will eventually give rise to larvae called cercariae
  • They leave the molluscan host and penetrate fish
  • They encyst in the fish tissues as the metacercaria
  • Consumption of infected fish results in the metacercaria excysting in the gut and migrating to the bile duct
slide21

Class Cestoda

  • Protective protein coat
  • anterior region is called a scolex;
  • oftenarmed with suckers and hooks
  • Extending from neck of scolex is a series of proglottids;
  • contain sex organs and eggs;
  • no digestive system
  • Mature eggs released through an opening in the proglottid
  • leave the host when the proglottids break off
slide22

b A definitive host eats infected, undercooked beef

a Larvae become encysted in intermediate host tissues

c Scolex of larva attaches to intestine’s wall

d Many proglottids form by budding

f Cattle may ingest embryonated eggs or ripe proglottids to become intermediate hosts

e Ripe proglottids containing fertilized eggs leave host in feces

Class Cestoda

Tapeworm Lifecycle

slide23

Beef Tapeworm, Taeniarhynchus saginatus

  • Definitive host = humans;
  • intermediate host = cattle
  • Eggs are shed with human feces;
  • infected persons defecate in a pasture or untreated sewage
  • eggs are ingested by cattle
  • Eggs hatch
  • larvae bore into intestinal wall
  • get into the circulatory system
  • transported to muscle
  • If uncooked beef is consumed the larvae is freed
  • scolex develops, forming the adult
  • Symptoms include loss of weight, chronic indigestion, diarrhea