Phylum Platyhelminthes Flatworms Monogenian Flukes Tapeworms

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

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

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

Flatworm Body Plans bilateral symmetry Acoelomate triploblastic

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

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

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

Feeding Habits

Excretion Excretory system Contains flame bulbs 12 Flatworms have the first true excretory system. Special cells called flame cells are located near the head of the animal. These cells have large flagella in them that wave, creating a low pressure area. The flame cells are connected to the rest of the body by a pair of lateral excretory ducts. Wastes are pulled from body cells into the ducts. Once in the ducts, the wastes move toward the flame cells. Once the wastes get to the flame cells they are released through a dorsal excretory pore. 12 12

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

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

Mating & Reproduction Chemosensory to find mate Hermaphroditic

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

Camouflage flatworm nudibranch

Toxins Staurosporine Tetrodoxin < Staurosporine and its derivatives belong to a group of organic chemical compounds called indolocarbazole alkaloids. They are known as potent antibiotics and strong insecticides.  Two of these compounds, 3-hydroxy-3'-demethoxy-3'-hydroxystaurosporine and 11-hydroxy-4'-N-demethylstaurosporine, were isolated from the marine polyclad flatworm Pseudoceros concineus and his favored food, the ascidian Eudistoma toealensis (Tunicata). Both animals are brightly coloured and show a high abundance in the mangroves of Truk Lagoon, Micronesia. Feeding experiments with tropical reef fish showed that the crude extract from the ascidian was highly deterrent towards fish, suggesting that staurosporine acts as a highly potent chemical defence substance against predators (Schupp et al., 1997). It is not known yet, wether the flatworm's metabolism is able to produce staurosporine by itself. It is more likely that the actual source of the toxic compound is the ascidian. After feeding on the poisonous tunicate the polyclad flatworm becomes unpalatable because it stores the toxin in his own tissues.  < Tetrodotoxin is a non-protein organic compound (aminoperhydroquinazoline) and one of the strongest paralytic toxins known today. It is a very specific blocker of voltage-gated Sodium (Na+) channels, large integral membrane proteins that form pores through the plasma membrane of neuronal cells that allow Na+ ions to cross. Pores (=gates) open and close in response to a variety of stimuli such as changes in membrane potential or the presence of certain chemicals outside or inside the cell. Their proper functioning is absolutely essential for neuronal action potentials. Tetrododoxin, however, blocks these channels irreversibly leading to rapid paralysis through interference with neuromuscular conduction.

Class Turbellaria Hawaiian Flatworms

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

Class Cestoda (Tapeworms) Defining characteristics Scolex Proglottids 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

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

Trematodes of Concern 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