Phylum Platyhelminthes 1 Flatworms Flukes Tapeworms

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

Phylum Platyhelminthes 3 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 4 Nervous System Free-living species usually have a well-developed sensory system Parasites generally have less elaborate systems. WHY?

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

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

Phylum Platyhelminthes 7 Flatworm Body Plans Exhibit bilateral symmetry, acoelomate, and are triploblastic Parenchyma tissue

Phylum Platyhelminthes 8 Digestion and Excretion Mouth is usually located at the anterior end or mid-body on ventral surface Excretory system – Contains flame bulbs

Phylum Platyhelminthes 9 Regeneration Many species posses remarkable powers of regeneration and repair wounds

Phylum Platyhelminthes 10 Turbellarian Lifestyles Most are benthic Posses several nerve cords with a centralized ganglia (brain)

Phylum Platyhelminthes 11 Turbellarian 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

Nervous System

Phylum Platyhelminthes 13 Reproduction Reproduction occurs with the reciprocal exchange of sperm Fertilized eggs are released and usually develop directly into flatworms – Muller's larva

Chemosensory to find mate Hermaphroditic Mating & Reproduction

Feeding

flatworm nudibranch Camouflage

Staurosporine Tetrodoxin

Hawaiian Flatworms Class Turbellaria

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

Phylum Platyhelminthes 20 Class Cestoda (Tapeworms) Defining characteristics – Scolex – Proglottids

Phylum Platyhelminthes 21 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 22 Beef tapeworm

Phylum Platyhelminthes 23 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 24 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 25 Trematoda Lifecycles The lifecycle is complex with up to 4 different hosts and several larval types

Phylum Platyhelminthes 26 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