Phylum Platyhelminthes Classes: Flatworms (Turbellaria) Flukes (Trematoda) Tapeworms (Cestoda) Monogeneans Phylum Platyhelminthes

Phylum Platyhelminthes They are Acoelomates because they lack body cavity (Coelom). This gives them a flat body structure (Flat worms) Phylum Platyhelminthes

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

Phylum Platyhelminthes Taxonomic Summary Phylum Platyhelminthes

Phylum Platyhelminthes

Phylum Platyhelminthes CHARACTERISTICS BILATERAL SYMMETRY THREE GERM LAYERS (TRIPLOBLASTIC) CENTRALIZED NERVOUS SYSTEM SIMPLE EXCRETORY SYSTEM COMPLEX REPRODUCTIVE SYSTEM SIMPLE DIGESTIVE SYSTEM Phylum Platyhelminthes

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

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

Phylum Platyhelminthes Class Turbellaria Most are free–living, tiny and inconspicuous Primarily marine and freshwater e.g Planaria Free-living Flatworm Phylum Platyhelminthes

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

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

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

Class Cestoda (Tapeworms) Defining characteristics Scolex Proglottids All parasitic E.g Taenia saginatta (beef tapeworm) Taenia solium (pork tapeworm) Phylum Platyhelminthes

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

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. Blood flukes (Shistosomes),Liver flukes (Fasciola) & Lung flukes (Paragonimus) Phylum Platyhelminthes

Schistosomes (Blood Fluke) Causes infection known as Schistosomiasis (Formally Bilharziasis) They are dioecious (Sexes are separted) Adult males carry females in a gynaecophoric canal. Phylum Platyhelminthes

Phylum Platyhelminthes Schistosome species Species Snail intermediate host Location in host veins Type of eggs spine S. mansoni Biomphalaria Large intestine Lateral spine S. japonicum Onchomelenia Small intestine Small round knob S. haematobium Bulinus Urinary bladder Terminal spine Phylum Platyhelminthes

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

Phylum Platyhelminthes Life Cycle of Blood fluke (Schistosomes) Trematodes of Concern 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 Phylum Platyhelminthes

Liver Fluke (Fasciola) Causes fascioliasis or liver rot in sheeps and dogs. Major examples : F. Hepatica & F. Gigantica Snail intermediate host- Lymnaea Phylum Platyhelminthes

Phylum Platyhelminthes Life cycle of Liver fluke (Fasciola) Phylum Platyhelminthes