Phylum Platyhelminthes

Phylum Platyhelminthes Flatworms Flukes Tapeworms Phylum Platyhelminthes

Phylum Platyhelminthes • The phylum consists of four classes • Turbellaria • Trematoda • Cestoda Triclad Flatworm Phylum Platyhelminthes

Reproduction • 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 • Free-living species usually have a well-developed sensory system • Parasites generally have less elaborate systems. WHY? Phylum Platyhelminthes

Taxonomic Summary • Phylum Platyhelminthes (Flatworms) • Class Turbellaria • Class Cestoda • Class Trematoda • Class Monogeneans Phylum Platyhelminthes

Class Turbellaria • Most are free–living, tiny and inconspicuous • Primarily marine and freshwater Free-living Flatworm Phylum Platyhelminthes

Flatworm Body Plans • Exhibit bilateral symmetry, acoelomate, and are triploblastic • Parenchyma tissue Phylum Platyhelminthes

Digestion and Excretion • Mouth is usually located at the anterior end or mid-body on ventral surface • Excretory system • Contains flame bulbs Phylum Platyhelminthes

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

Turbellarian Lifestyles • Most are benthic • Posses several nerve cords with a centralized ganglia (brain) Phylum Platyhelminthes

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 Turbellarian Habits Phylum Platyhelminthes

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

Defining characteristics Scolex Proglottids Class Cestoda (Tapeworms) Phylum Platyhelminthes

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 Phylum Platyhelminthes

Beef tapeworm Phylum Platyhelminthes

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 Phylum Platyhelminthes

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 Platyhelminthes

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

Schistosomiasis Deadly prominent disease in many regions of the world Bores into the skin of the definitive host and travels in the circulatory system to the heart the lungs and the kidneys where it feeds and grows Inflammation is caused by eggs becoming trapped in the hosts tissues Chinese liver fluke Lives in the bile duct of humans, cats, and dogs (1-2 cm.) Goes through two intermediate hosts Infection occurs from ingestion of raw fish Trematodes of Concern Phylum Platyhelminthes

Phylum Platyhelminthes