Phylum Platyhelminthes Flatworms 1 Flukes Monogenian Tapeworms Phylum

Phylum Platyhelminthes Flatworms 1 Flukes Monogenian Tapeworms

Phylum Platyhelminthes The phylum consists of four classes – – 2 Turbellaria (flatworm) Trematoda (fluke) Cestoda (tapeworm) Monogenian

Reproduction l l l 3 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 Phylum Platyhelminthes

Nervous System l Free-living species usually have a welldeveloped sensory system l Parasites generally have less elaborate systems. WHY? 4 Phylum Platyhelminthes

Taxonomic Summary l Phylum Platyhelminthes (Flatworms) Class Turbellaria – Class Cestoda – Class Trematoda – Class Monogeneans – 5 Phylum Platyhelminthes

Class Turbellaria Most are free–living, benthic, tiny and inconspicuous – Free-living – Primarily marine and freshwater, many interstitial 4, 500 species Flatworm 6 Phylum Platyhelminthes

Flatworm Body Plans bilateral symmetry l Acoelomate l triploblastic l 7

Digestion l l 8 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

Digestion l 9 Mouth is usually located at the anterior end or mid-body on ventral surface

Feeding Habits l 10 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

Feeding Habits

Excretion l Excretory system – Contains flame bulbs 12

Nervous System l Posses several nerve cords with a centralized ganglia (brain)

Reproduction occurs with the reciprocal exchange of sperm l Fertilized eggs are released and usually develop directly into flatworms l – 14 Muller's larva Phylum Platyhelminthes

Mating & Reproduction • Chemosensory to find mate • Hermaphroditic

Regeneration l 16 Many species posses remarkable powers of regeneration and repair wounds Phylum Platyhelminthes

Camouflage flatworm nudibranch

• Staurosporine • Tetrodoxin

Class Turbellaria Hawaiian Flatworms

Hawaiian Flatworms Pseudoceros cf. rubroanus Pseudoceros ferrugineus Planocera cf. oligoglena Pseudoceros dimidiatus Pseudobiceros sp. Class Turbellaria

Class Cestoda (Tapeworms) l Defining characteristics Scolex – Proglottids – 21 Phylum Platyhelminthes

Proglottids l 22 Proglottids – Each animal can be 3, 000 – 4, 000 per animal – Amazing reproductive output – Each may contain several ovaries and 1, 000 distinct testes Phylum Platyhelminthes

Problems of a parasitic existence Reproduce within the definitive host l Get fertilized eggs out of the host l Contact a new and appropriate host l Obtain entrance into the host l Locate the appropriate environment within the host l Maintain position within the host l Withstand an often anaerobic environment l Avoid digestion or attack by the hosts immune system l Avoid killing the host, at least until reproduction 23 is completed Phylum Platyhelminthes l

Class Trematoda (Flukes) l l l 24 All are external and internal parasites of other animals Leech-like bodies with a sucker at each end Have a gut and welldeveloped reproductive system, never segmented

Trematoda Lifecycles l 25 The lifecycle is complex with up to 4 different hosts and several larval types Phylum Platyhelminthes

Trematodes of Concern 26

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