Class TrematodaSlide 2Slide 3TegumentSlide 5Digenean TrematodesSlide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Clonorchis liver flukeSlide 16How do flukes manipulate their hosts?Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24SchistosomiasisSlide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Do trematode parasites favor sex in hosts?Slide 38Slide 39Slide 40Slide 41Class MonogeneaSlide 43Slide 44Slide 45Slide 46Class Cestoda (tapeworms)Class CestodaSlide 49Slide 50Slide 51Slide 52Slide 53Slide 54Slide 55Human tapewormsSlide 57Slide 58Slide 59Slide 60Adult cestodiasisLarval cestodiasisHumans as intermediate hosts (larval cestodiasis)Slide 64Tapeworm manipulations of hostsSlide 66Slide 67Slide 68Slide 69Class TrematodaClass TrematodaThere are about 9000 species of There are about 9000 species of trematodes all of which are parasitic. trematodes all of which are parasitic. Most parasitize vertebrates. Most parasitize vertebrates. Adaptations for parasitism include Adaptations for parasitism include suckers and hooks for attachment, suckers and hooks for attachment, glands to produce cyst material and glands to produce cyst material and increased reproductive capacity.increased reproductive capacity.Sheep liver flukeClass TrematodaClass TrematodaStructurally, trematodes are similar Structurally, trematodes are similar to turbellarians having a well to turbellarians having a well developed digestive system and developed digestive system and similar nervous, excretory, and similar nervous, excretory, and reproductive systems. However, a reproductive systems. However, a major difference is the major difference is the tegumenttegument..TegumentTegumentThe tegument (found in all parasitic The tegument (found in all parasitic Platyhelminthes) is a nonciliated, Platyhelminthes) is a nonciliated, cytoplasmic syncytium that overlays layers cytoplasmic syncytium that overlays layers of muscle.of muscle.The syncytium represents extensions of cells The syncytium represents extensions of cells that are located below the muscle in the that are located below the muscle in the parenchyma.parenchyma.The tegument protects the parasite against The tegument protects the parasite against its host (e.g. against digestive enzymes).its host (e.g. against digestive enzymes).8.5Figure 14.05Digenean TrematodesDigenean TrematodesThere are three subclasses of There are three subclasses of Trematodes, but two are small, Trematodes, but two are small, poorly studied groups.poorly studied groups.The third group, the Digenea, The third group, the Digenea, however is a large group of major however is a large group of major medical and economic importance.medical and economic importance.Digenean TrematodesDigenean TrematodesThe flukes have a complex life cycle The flukes have a complex life cycle in which a snail is the first (or in which a snail is the first (or intermediate) host and a vertebrate intermediate) host and a vertebrate the final (or definitive host).the final (or definitive host).The definitive host is one in which The definitive host is one in which the fluke reproduces sexually.the fluke reproduces sexually.Digenean TrematodesDigenean TrematodesIn some species there may be 2 or 3 In some species there may be 2 or 3 intermediate hosts before the intermediate hosts before the definitive host is reached.definitive host is reached.Trematodes inhabit a variety of sites in Trematodes inhabit a variety of sites in their hosts including the digestive their hosts including the digestive tract, respiratory tract, circulatory tract, respiratory tract, circulatory system, urinary tract, and reproductive system, urinary tract, and reproductive tract.tract.Digenean TrematodesDigenean TrematodesDigenean life cycles are very Digenean life cycles are very complex and the fluke passes complex and the fluke passes through numerous stages.through numerous stages.Digenean TrematodesDigenean TrematodesA typical example would include the A typical example would include the following stages:following stages:AdultAdultEggEgg (or shelled embryo) shed into water (or shelled embryo) shed into waterMiracidiumMiracidium: a free swimming, ciliated : a free swimming, ciliated larva that finds and penetrates a snail larva that finds and penetrates a snail intermediate hostintermediate hostSheep liver fluke egg (top) and miracidium (bottom).http://cal.vet.upenn.edu/projects/paraav/images/lab6-227.jpgDigenean TrematodesDigenean TrematodesSporocystSporocyst: reproduces asexually in : reproduces asexually in intermediate host producing more intermediate host producing more sporocysts or another asexually sporocysts or another asexually reproducing stage called a reproducing stage called a redia.redia.Redia Redia produce more redia or cercariae. produce more redia or cercariae. Cercariae leave the intermediate host Cercariae leave the intermediate host and swim. Then they penetrate the skin and swim. Then they penetrate the skin of another intermediate host or the of another intermediate host or the definitive host.definitive host.Adult Fasciola hepatica Sheep liver fluke (above)Redia (right)http://cal.vet.upenn.edu/projects/paraav/images/lab6-227.jpgDigenean TrematodesDigenean TrematodesCercariaeCercariae that enter an intermediate host that enter an intermediate host may encyst in muscle and wait to be consumed may encyst in muscle and wait to be consumed by the definitive host or may leave the by the definitive host or may leave the intermediate host to actively search for the intermediate host to actively search for the definitive host.definitive host.CercariaeCercariae that enter the definitive host make that enter the definitive host make their way to their desired home and develop their way to their desired home and develop into an adult fluke which reproduces sexually into an adult fluke which reproduces sexually and produces eggs.and produces eggs.http://www.biology-blog.com/images/blogs/trematode-cercaria-482810.jpgClonorchisClonorchis liver fluke liver flukeClonorchisClonorchis is the most important liver fluke to is the most important liver fluke to infect humans. Common in much of Asia infect humans. Common in much of Asia (including China, Japan and southern Asia).(including China, Japan and southern Asia).Adult flukes live in the bile passages and shelled Adult flukes live in the bile