1 phylum platyhelminthes flatworms flukestapeworms monogenian
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Phylum Platyhelminthes
Flatworms
Flukes Tapeworms
Monogenian
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Phylum Platyhelminthes
The phylum consists of four classes
– Turbellaria (flatworm)– Trematoda (fluke)– Cestoda (tapeworm)– Monogenian
Phylum Platyhelminthes3
Almost all are simultaneous hermaphrodites
Parasitic species (flukes and tapeworms) have complex lifecycles, with various hosts and several different larval stages
Incredible powers of regeneration
Reproduction
Phylum Platyhelminthes4
Nervous SystemFree-living species usually have a well-developed
sensory system Parasites generally have less elaborate systems.
WHY?
Phylum Platyhelminthes5
Taxonomic Summary
Phylum Platyhelminthes (Flatworms)
– Class Turbellaria– Class Cestoda– Class Trematoda– Class Monogeneans
Phylum Platyhelminthes6
Class Turbellaria
Most are free–living, benthic, tiny and inconspicuous
– Primarily marine and freshwater, many interstitial
– 4,500 speciesFree-living
Flatworm
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Flatworm Body Plansbilateral symmetryAcoelomatetriploblastic
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Digestion Mouth is usually located at the anterior end or mid-body on
ventral surface Some species also have a protrusible pharynx that captures
food and transfers it into the mouth– Can be carnivores or scavenge on dead animals and
detritus
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DigestionMouth is usually located at the
anterior end or mid-body on ventral surface
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Feeding Habits Some species also have a protrusible pharynx that
captures food and transfers it into the mouth– Can be carnivores or scavenge on dead animals and
detritus
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Excretion
Excretory system – Contains
flame bulbs
Nervous System
Posses several nerve cords with a centralized ganglia (brain)
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ReproductionReproduction occurs
with the reciprocal exchange of sperm
Fertilized eggs are released and usually develop directly into flatworms– Muller's larva
Phylum Platyhelminthes16
Regeneration Many species posses remarkable powers of
regeneration and repair wounds
Pseudoceros dimidiatus
Pseudoceros cf. rubroanus
Pseudoceros ferrugineus
Pseudobiceros sp.
Planocera cf. oligoglena
Class Turbellaria
Hawaiian Flatworms
Phylum Platyhelminthes21
Class Cestoda (Tapeworms)
Defining characteristics– Scolex– Proglottids
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Proglottids Proglottids
– Each animal can be 3,000 – 4,000 per animal
– Amazing reproductive output
– Each may contain several ovaries and 1,000 distinct testes
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Problems of a parasitic existence Reproduce within the definitive host Get fertilized eggs out of the host Contact a new and appropriate host Obtain entrance into the host Locate the appropriate environment within the host Maintain position within the host Withstand an often anaerobic environment Avoid digestion or attack by the hosts immune system Avoid killing the host, at least until reproduction is
completed
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Class Trematoda (Flukes)
All are external and internal parasites of other animals
Leech-like bodies with a sucker at each end
Have a gut and well-developed reproductive system, never segmented
Phylum Platyhelminthes25
Trematoda Lifecycles
The lifecycle is complex with up to 4 different hosts and several larval types
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