1. Bilateria Having completed the radially symmetrical Cnidarians and Ctenophores we now move on to the remaining animals, all of which are bilaterally symmetrical (or secondarily radially symmetrical [the Echinoderms]). Having completed the radially symmetrical Cnidarians and Ctenophores we now move on to the remaining animals, all of which are bilaterally symmetrical (or secondarily radially symmetrical [the Echinoderms]). These are the Bilateria. These are the Bilateria.

2. Bilateria All Bilateria are triploblastic and belong to two major groups, which we have already met, the Protostomia and the Deuterostomia. All Bilateria are triploblastic and belong to two major groups, which we have already met, the Protostomia and the Deuterostomia. Deuterostomes include the Echindoerms, Hemichordates and Chordates. Deuterostomes include the Echindoerms, Hemichordates and Chordates. Protostomes include all the other bilateral invertebrates including Platyhelminthes, Annelida, Mollusca, and Arthropoda. Protostomes include all the other bilateral invertebrates including Platyhelminthes, Annelida, Mollusca, and Arthropoda.

5. Protostomia divisions Classification of invertebrates is in a state of flux for several reasons: Classification of invertebrates is in a state of flux for several reasons: molecular phylogenetic studies have cast doubt on traditional invertebrate classification based on morphological characteristics. molecular phylogenetic studies have cast doubt on traditional invertebrate classification based on morphological characteristics. many invertebrates are soft-bodied so fossils of many groups are rare or unknown, which makes relationships between groups hard to decipher. many invertebrates are soft-bodied so fossils of many groups are rare or unknown, which makes relationships between groups hard to decipher. Traditional major groups of protostomes (acoelomate, pseudocoelomate and coelomate) appear not to be monophyletic. Traditional major groups of protostomes (acoelomate, pseudocoelomate and coelomate) appear not to be monophyletic.

6. Protostomia divisions For this class, we will use the Deuterostome/Protostome arrangement and recognize two majors groups of Protostomes: the Lophotrochozoa and the Ecdysozoa. For this class, we will use the Deuterostome/Protostome arrangement and recognize two majors groups of Protostomes: the Lophotrochozoa and the Ecdysozoa.

7. Protostome Divisions: the Lophotrochozoa and Ecdysozoa. Protostomes are divided into two large groups the Lophotrochozoa and the Ecdysozoa. Protostomes are divided into two large groups the Lophotrochozoa and the Ecdysozoa. The relatedness of phyla within these two groups is not entirely clear and will likely change in the future. The relatedness of phyla within these two groups is not entirely clear and will likely change in the future.

8. Lophotrochozoa and Ecdysozoa Lophotrochozoa: members generally possess a trochophore larva [free-swimming oval or pyramidal ciliated larva with a band of cilia around the body] or a lophophore [tentacle bearing arm which contains within it an extension of the coelomic cavity]. Lophotrochozoa: members generally possess a trochophore larva [free-swimming oval or pyramidal ciliated larva with a band of cilia around the body] or a lophophore [tentacle bearing arm which contains within it an extension of the coelomic cavity]. Ecdysozoa: members shed their cuticle as they grow Ecdysozoa: members shed their cuticle as they grow

9. Trochophore larva http://www.microscopy-uk.org.uk/mag/imgjan09/image006.jpg

10. Trochophore larva clip Trochophore larva clip https://www.youtube.com/watch?v=Z0cE OvGcrl8 https://www.youtube.com/watch?v=Z0cE OvGcrl8 https://www.youtube.com/watch?v=Z0cE OvGcrl8 https://www.youtube.com/watch?v=Z0cE OvGcrl8

11. Lophophore: characteristic feeding structure of members of the Brachiopoda, Bryozoa and Phoronida Bryozoan lophophore http://www.bryozoans.nl/pictures/ figuren/anatomy.jpg

12. Lophophore clip Lophophore clip https://www.youtube.com/watch?v=Op3- FEVwa0E https://www.youtube.com/watch?v=Op3- FEVwa0E https://www.youtube.com/watch?v=Op3- FEVwa0E https://www.youtube.com/watch?v=Op3- FEVwa0E

13. Lophotrochozoa and Ecdysozoa Lophotrochozoa members: Lophotrochozoa members: Platyhelminthes, Annelida, Mollusca, and a diverse array of “lesser phyla” including Nemertea, Rotifera, Acanthocephala, Brachiopoda, and Sipuncula. Platyhelminthes, Annelida, Mollusca, and a diverse array of “lesser phyla” including Nemertea, Rotifera, Acanthocephala, Brachiopoda, and Sipuncula. Ecdysozoa members: Ecdysozoa members: Nematoda, Arthropoda and “lesser phyla” including Onychophora, Tardigrada, Kinorhyncha, and Priapulida. Nematoda, Arthropoda and “lesser phyla” including Onychophora, Tardigrada, Kinorhyncha, and Priapulida.

14. Ecdysozoa : Onychophora, Tardigrada, Arthropoda, Nematoda, Nematomorpha, Kinorhyncha, Loricifera, Priapulida Gastrotricha Cuticulata Protostomia Lophotrochozoa Eutrochozoa : Rotifera, Acanthocephala, Entoprocta,Platyhelminthes, Nemertea, Mollusca, Sipuncula, Annelida Lophophorata : Ectoprocta, Brachiopoda, Phoronida

15. Ectoprocta Brachiopoda Phoronida Lophophorata Lophotrochozoa Rotifera Acanthocephala Platyhelminthes Annelida Sipuncula Entoprocta Nemertea Mollusca Parenchymia

16. “Worms” The term worm is loosely employed in biology and is applied to very different animals including the segmented worms (Annelids), roundworms (Nematoda) ribbonworms (Nemertea) flatworms (Platyhelminthes) and others. The term worm is loosely employed in biology and is applied to very different animals including the segmented worms (Annelids), roundworms (Nematoda) ribbonworms (Nemertea) flatworms (Platyhelminthes) and others. “Worm” describes any bilaterally symmetrical, legless, soft-bodied animal at least 2-3 times as long as it is wide. “Worm” describes any bilaterally symmetrical, legless, soft-bodied animal at least 2-3 times as long as it is wide.

17. Phylum Platyhelminthes Unlike other animals encountered so far, Platyhelminthes: Unlike other animals encountered so far, Platyhelminthes: have evolved cephalization with their sense organs concentrated at the head end. have evolved cephalization with their sense organs concentrated at the head end. Have a ladder-type nervous system. Have a ladder-type nervous system. are bilaterally symmetrical. are bilaterally symmetrical. Are dorsoventrally flattened. Are dorsoventrally flattened.

18. Phylum Platyhelminthes In addition they are In addition they are triploblastic, but lack a coelom. Instead, they have a solid body filled with parenchyma cells. triploblastic, but lack a coelom. Instead, they have a solid body filled with parenchyma cells. have evolved organs and in some cases organ systems. have evolved organs and in some cases organ systems. The first (and simplest) excretory or osmoregulatory systems and circulatory systems are found in members of these groups. The first (and simplest) excretory or osmoregulatory systems and circulatory systems are found in members of these groups.

20. Phylum Platyhelminthes Platyhelminthes usually slender and leaflike or ribbonlike. Unsegmented. Platyhelminthes usually slender and leaflike or ribbonlike. Unsegmented. Have no circulatory or respiratory organs. Flat body increases surface area and allows the animal to exchange gas and lose wastes by diffusion. Have no circulatory or respiratory organs. Flat body increases surface area and allows the animal to exchange gas and lose wastes by diffusion. Four classes in the Platyhelminthes. Turbellaria are free living but the Monogenea, Trematoda and Cestoda are parasitic. Four classes in the Platyhelminthes. Turbellaria are free living but the Monogenea, Trematoda and Cestoda are parasitic.

21. Nutrition The digestive system includes a mouth, pharynx, and blind intestine (the gut is incomplete). The digestive system includes a mouth, pharynx, and blind intestine (the gut is incomplete). In the free-living Turbellarians the pharynx can be everted from the mouth. In the free-living Turbellarians the pharynx can be everted from the mouth. Food is sucked into the intestine where a combination of extracellular and intracellular digestion takes place. Food is sucked into the intestine where a combination of extracellular and intracellular digestion takes place.

22. http://www.thaigoodview.com/library/contest2551/science04/119 /kingdon_animalia/images/turbellaria4.jpg

23. “Organization of the blind digestive cavity of polyclads [a group of Turbellarians] with highly branched diverticles (ventral view)” http://www.rzuser.uni-heidelberg.de/~bu6/Introduction04.html

24. Nutrition Undigested food exits via the pharynx. Undigested food exits via the pharynx. In the Cestoda the digestive tract is absent and all nutrients are absorbed across the tegument (the syncytial membrane/body covering found in all parasitic Platyhelminthes). In the Cestoda the digestive tract is absent and all nutrients are absorbed across the tegument (the syncytial membrane/body covering found in all parasitic Platyhelminthes).

25. Excretion/Osmoregulation The osmoregulatory system consists of a series of canals that end in flame cells or protonephridia. The osmoregulatory system consists of a series of canals that end in flame cells or protonephridia. The flame cell consists of a fine-meshed cup that contains cilia. The beating of the cilia draws fluid which is filtered as it passes into the cup. The flame cell consists of a fine-meshed cup that contains cilia. The beating of the cilia draws fluid which is filtered as it passes into the cup. This system appears mainly intended to remove excess fluid, but retain essential ions. It is most developed in freshwater Turbellarians, but reduced or absent in marine species, which do not have to remove excess water. This system appears mainly intended to remove excess fluid, but retain essential ions. It is most developed in freshwater Turbellarians, but reduced or absent in marine species, which do not have to remove excess water.

26. http://www.cartage.org.lb/en/themes/Sciences/Lifescience/GeneralBiology/ Physiology/ExcretorySystem/Invertebrate/flatwormexcret.gif

27. Flame cells at 1000x magnification https://www.youtube.com/watch?v=Rb_3 KIB4CmE https://www.youtube.com/watch?v=Rb_3 KIB4CmE https://www.youtube.com/watch?v=Rb_3 KIB4CmE https://www.youtube.com/watch?v=Rb_3 KIB4CmE

28. Nervous system and sense organs Flatworms possess a simple brain and one to five pairs of longitudinal nerve cords that are cross connected to form a ladder-like arrangement. Flatworms possess a simple brain and one to five pairs of longitudinal nerve cords that are cross connected to form a ladder-like arrangement.

29. Nervous system of Dugesia http://biodidac.bio.uottawa.ca/ftp/BIODIDAC/ZOO/PLATYHEL/DIAGCL/TURB007C.GIF

30. Nervous system and sense organs Neurons are specialized for different tasks e.g. sensory and motor functions, which is an important advance in the evolution of nervous systems. Neurons are specialized for different tasks e.g. sensory and motor functions, which is an important advance in the evolution of nervous systems. There are a number of different sensory cells found in flatworms and tactile and chemoreceptive cells are abundant. There are a number of different sensory cells found in flatworms and tactile and chemoreceptive cells are abundant.

31. Nervous system and sense organs In freshwater Planarians concentrations of sensory cells form two ear-like structures (the auricles) found on the side of the head. In freshwater Planarians concentrations of sensory cells form two ear-like structures (the auricles) found on the side of the head. Light sensitive eyespots or ocelli are common in all classes but Cestoda. Light sensitive eyespots or ocelli are common in all classes but Cestoda.

32. Freshwater Planarians: http://www.aecos.com/CPIE/flatworm.jpg

33. Reproduction Reproduction in the Platyhelminthes can be asexual or sexual. However, most are hermaphroditic and cross fertilize. Reproduction in the Platyhelminthes can be asexual or sexual. However, most are hermaphroditic and cross fertilize. In parasitic forms sexual and asexual reproduction may alternate in different stages of the life history In parasitic forms sexual and asexual reproduction may alternate in different stages of the life history

34. Penis fencing in Turbellarians https://www.youtube.com/watch?v=wn3xl uIRh1Y https://www.youtube.com/watch?v=wn3xl uIRh1Y https://www.youtube.com/watch?v=wn3xl uIRh1Y https://www.youtube.com/watch?v=wn3xl uIRh1Y

35. Classification of Platyhelminthes There are four classes in the Platyhelminthes: There are four classes in the Platyhelminthes: Class Turbellaria: free-living flatworms. Class Turbellaria: free-living flatworms. Class Trematoda: endoparasitic flukes Class Trematoda: endoparasitic flukes Class Monogenea: parasitic flukes that are mainly ectoparasites Class Monogenea: parasitic flukes that are mainly ectoparasites Class Cestoda: tapeworms Class Cestoda: tapeworms

36. Class Turbellaria Class Turbellaria contains about 3000 species. There is considerable debate about the classification of the class and it is likely that the class is not monophyletic. Class Turbellaria contains about 3000 species. There is considerable debate about the classification of the class and it is likely that the class is not monophyletic. Most species are marine and benthic (move around on the bottom in aquatic environments). Most species are marine and benthic (move around on the bottom in aquatic environments). Some also found in fresh water or in moist temperate and tropical terrestrial habitats. Some also found in fresh water or in moist temperate and tropical terrestrial habitats.

37. 8.2 Marine turbellarian

38. Dugesia tigrina, a freshwater turbellarian © Mauricio A. Muñoz

39. Class Turbellaria Most Turbellarians are predators of invertebrates smaller than themselves. A few are herbivores or scavengers. Most Turbellarians are predators of invertebrates smaller than themselves. A few are herbivores or scavengers. In many species the pharynx is protrusible and can be inserted into the prey to begin digesting it. Some species stab prey with their penis (it has a hardened tip or stylet). In many species the pharynx is protrusible and can be inserted into the prey to begin digesting it. Some species stab prey with their penis (it has a hardened tip or stylet).

40. Predatory flatworm hunting snails. https://www.youtube.com/watch?v=3DU_ pvAtIYQ https://www.youtube.com/watch?v=3DU_ pvAtIYQ https://www.youtube.com/watch?v=3DU_ pvAtIYQ https://www.youtube.com/watch?v=3DU_ pvAtIYQ

41. Class Turbellaria Turbellarians move by swimming, creeping or crawling. They combine muscular contractions with ciliary movement to move. Turbellarians move by swimming, creeping or crawling. They combine muscular contractions with ciliary movement to move. Turbellarians may also use waves of muscle movement to move. Turbellarians may also use waves of muscle movement to move.

42. Swimming marine turbellarian https://www.youtube.com/watch?v=7UkZ HDIujUc https://www.youtube.com/watch?v=7UkZ HDIujUc https://www.youtube.com/watch?v=7UkZ HDIujUc https://www.youtube.com/watch?v=7UkZ HDIujUc

43. “Polycladida moseleyi is distributed throughout the Mediterranean Sea and the temperate eastern Atlantic. Its favored food are tunicates (Clavelina sp.). “ http://www.rzuser.uni-heidelberg.de/~bu6/flat0431.html

44. Class Trematoda There are about 9000 species of trematodes (flukes) all of which are parasitic. Most parasitize vertebrates. There are about 9000 species of trematodes (flukes) all of which are parasitic. Most parasitize vertebrates. Adaptations for parasitism include suckers and hooks for attachment, glands to produce cyst material and increased reproductive capacity. Adaptations for parasitism include suckers and hooks for attachment, glands to produce cyst material and increased reproductive capacity.

45. Sheep liver fluke

46. Class Trematoda Structurally trematodes are similar to turbellarians having a well developed digestive system and similar nervous, excretory, and reproductive systems. However, a major difference is the tegument. Structurally trematodes are similar to turbellarians having a well developed digestive system and similar nervous, excretory, and reproductive systems. However, a major difference is the tegument.

47. Tegument The tegument (found in all parasitic Platyhelminthes) is a nonciliated, cytoplasmic syncytium that overlays layers of muscle. The tegument (found in all parasitic Platyhelminthes) is a nonciliated, cytoplasmic syncytium that overlays layers of muscle. The syncytium represents extensions of cells that are located below the muscle in the parenchyma. The syncytium represents extensions of cells that are located below the muscle in the parenchyma. The tegument protects the parasite against its host (e.g. against digestive enzymes). The tegument protects the parasite against its host (e.g. against digestive enzymes).

48. 8.5

49. Digenean Trematodes There are three subclasses of Trematodes, but two are small, poorly studied groups. There are three subclasses of Trematodes, but two are small, poorly studied groups. The third group, the Digenea, however is a large group of major medical and economic importance. The third group, the Digenea, however is a large group of major medical and economic importance.

50. Digenean Trematodes Flukes have a complex life cycle in which a snail is the first (or intermediate) host and a vertebrate the final (or definitive host). Flukes have a complex life cycle in which a snail is the first (or intermediate) host and a vertebrate the final (or definitive host). The definitive host is one in which the fluke reproduces sexually. The definitive host is one in which the fluke reproduces sexually.

51. Digenean Trematodes In some species there may be 2 or 3 intermediate hosts before the definitive host is reached. In some species there may be 2 or 3 intermediate hosts before the definitive host is reached. Trematodes inhabit a variety of sites in their hosts including the digestive tract, respiratory tract, circulatory system, urinary tract, and reproductive tract. Trematodes inhabit a variety of sites in their hosts including the digestive tract, respiratory tract, circulatory system, urinary tract, and reproductive tract.

52. Digenean Trematodes Digenean life cycles are very complex and the fluke passes through numerous stages. Digenean life cycles are very complex and the fluke passes through numerous stages.

53. Digenean Trematodes A typical example would include the following stages: A typical example would include the following stages: Adult Adult Egg (or shelled embryo) shed into water Egg (or shelled embryo) shed into water Miracidium: a free swimming, ciliated larva that finds and penetrates a snail intermediate host Miracidium: a free swimming, ciliated larva that finds and penetrates a snail intermediate host

54. Hatching schistomsome miracdia https://www.youtube.com/watch?v=qPqW TY80UzE https://www.youtube.com/watch?v=qPqW TY80UzE https://www.youtube.com/watch?v=qPqW TY80UzE https://www.youtube.com/watch?v=qPqW TY80UzE

55. Digenean Trematodes Sporocyst: reproduces asexually in intermediate host producing more sporocysts or another asexually reproducing stage called a redia. Sporocyst: reproduces asexually in intermediate host producing more sporocysts or another asexually reproducing stage called a redia. Redia produce more redia or cercariae. Redia produce more redia or cercariae. Cercariae leave the intermediate host and swim. Then they penetrate the skin of another intermediate host or the definitive host. Cercariae leave the intermediate host and swim. Then they penetrate the skin of another intermediate host or the definitive host.

56. Cercariae https://www.youtube.com/watch?v=Dy6S hA04qT0 https://www.youtube.com/watch?v=Dy6S hA04qT0 https://www.youtube.com/watch?v=Dy6S hA04qT0 https://www.youtube.com/watch?v=Dy6S hA04qT0

57. Digenean Trematodes Cercariae that enter an intermediate host encyst in muscle and wait to be consumed by the definitive host. Cercariae that enter an intermediate host encyst in muscle and wait to be consumed by the definitive host. Cercariae that enter the definitive host make their way to their desired home and develop into an adult fluke which reproduces sexually and produces eggs. Cercariae that enter the definitive host make their way to their desired home and develop into an adult fluke which reproduces sexually and produces eggs.

58. Clonorchis liver fluke Clonorchis is the most important liver fluke to infect humans. Common in much of Asia (including China, Japan and southern Asia). Estimated 30 million people infected. Clonorchis is the most important liver fluke to infect humans. Common in much of Asia (including China, Japan and southern Asia). Estimated 30 million people infected. Adult flukes live in the bile passages and shelled miricidia pass out in feces. The miricidia enter snails eventually leave the snails as cercariae and find a fish where they encyst. Adult flukes live in the bile passages and shelled miricidia pass out in feces. The miricidia enter snails eventually leave the snails as cercariae and find a fish where they encyst. If fish is eaten raw or poorly cooked the person becomes infected If fish is eaten raw or poorly cooked the person becomes infected

59. 8.8

60. How do flukes manipulate their hosts? Many parasites infect an intermediate host that needs to be eaten by the definitive host for the parasite to complete its lifecycle. Many parasites infect an intermediate host that needs to be eaten by the definitive host for the parasite to complete its lifecycle. There are many instances of parasites altering their intermediate hosts behavior to make it more vulnerable a predator (the definitive host). Such behavior is widespread in flukes. There are many instances of parasites altering their intermediate hosts behavior to make it more vulnerable a predator (the definitive host). Such behavior is widespread in flukes.

61. How do flukes manipulate their hosts? The fluke Euhaplorchis californiensis lives in the Carpenteria Salt Marshes in southern California. The fluke Euhaplorchis californiensis lives in the Carpenteria Salt Marshes in southern California. Life cycle includes two intermediate hosts, first the California Horn Snail and then the California killifish and a final host: fish eating birds e.g. gulls. Life cycle includes two intermediate hosts, first the California Horn Snail and then the California killifish and a final host: fish eating birds e.g. gulls.

62. How do flukes manipulate their hosts? Fluke eggs contained in bird droppings which are eaten by the fluke’s first intermediate host the snail. Fluke eggs contained in bird droppings which are eaten by the fluke’s first intermediate host the snail. The fluke castrates the snail (so host does not “waste” energy reproducing) leaving more resources for the fluke to use. The fluke castrates the snail (so host does not “waste” energy reproducing) leaving more resources for the fluke to use. Fluke then reproduces asexually in snail and sheds cercariae into the water. Fluke then reproduces asexually in snail and sheds cercariae into the water.

63. How do flukes manipulate their hosts? Cercariae seek out the next intermediate host the killifish and latch onto the fish’s gills. Cercariae seek out the next intermediate host the killifish and latch onto the fish’s gills. Each cercaria works its way into a blood vessel, then seeks out a nerve and follows it to the fish’s brain. Each cercaria works its way into a blood vessel, then seeks out a nerve and follows it to the fish’s brain.

64. How do flukes manipulate their hosts? Cercariae don’t penetrate the brain but sit on top of it and wait for the fish to be eaten by a bird. Cercariae don’t penetrate the brain but sit on top of it and wait for the fish to be eaten by a bird. Once eaten by a bird cercariae move into the bird’s gut, transform into adults and produce eggs that continue the cycle Once eaten by a bird cercariae move into the bird’s gut, transform into adults and produce eggs that continue the cycle

65. How do flukes manipulate their hosts? Cercariae on the fish’s brain manipulate the fish’s behavior. Cercariae on the fish’s brain manipulate the fish’s behavior. Killifish when swimming sometimes shimmy and jerk around flashing their bellies. Fish infected with cercariae are four times more likely to do so than non- infected fish. Killifish when swimming sometimes shimmy and jerk around flashing their bellies. Fish infected with cercariae are four times more likely to do so than non- infected fish.

66. How do flukes manipulate their hosts? In field experiments in which penned fish were made available to foraging birds infected fish were 30 times (!) more likely to be eaten than uninfected fish. In field experiments in which penned fish were made available to foraging birds infected fish were 30 times (!) more likely to be eaten than uninfected fish.

67. How do flukes manipulate their hosts? Research has shown that the flukes produce powerful molecular signals called fibroblast growth factors. Research has shown that the flukes produce powerful molecular signals called fibroblast growth factors. These interfere with the growth of nerves and may be the mechanism the flukes use to alter the fish’s behavior. These interfere with the growth of nerves and may be the mechanism the flukes use to alter the fish’s behavior.

68. Schistosomiasis Schsitosomiasis is an infection with blood flukes and is one of the most important major infectious diseases on the planet. Schsitosomiasis is an infection with blood flukes and is one of the most important major infectious diseases on the planet. More then 200 million people are infected worldwide with these flukes which they acquire swimming or walking in water in which the intermediate snail host lives More then 200 million people are infected worldwide with these flukes which they acquire swimming or walking in water in which the intermediate snail host lives

69. "Schistosomiasis Life Cycle" by Unknown - CDC DPDx. Licensed under Public Domain via Commons - https://commons.wikimedia.org/wiki/File:Schistosomiasis_Life_Cycle.png#/media/File:Schistosomiasis_L ife_Cycle.png

70. Schistosomiasis When a schistosome cercaria swims it avoids UV light which can damage it, but is very sensitive to the scent of humans. When a schistosome cercaria swims it avoids UV light which can damage it, but is very sensitive to the scent of humans. When it senses molecules from human skin it swims rapidly and jerks around looking for the person. When it makes contact it releases chemicals that soften the skin and burrows in shedding its tail at the same time. When it senses molecules from human skin it swims rapidly and jerks around looking for the person. When it makes contact it releases chemicals that soften the skin and burrows in shedding its tail at the same time.

71. Schistosomiasis The fluke searches until it finds a capillary and enters it. It moves along using its pair of suckers. The fluke searches until it finds a capillary and enters it. It moves along using its pair of suckers. Eventually, it makes its way to the liver. Eventually, it makes its way to the liver.

72. Schistosomiasis In the liver, the fluke feeds on blood and grows and becomes sexually mature. In the liver, the fluke feeds on blood and grows and becomes sexually mature. It attracts a mate by chemical signaling. It attracts a mate by chemical signaling. Females are slender and delicate, whereas males are much bigger and have a spiny trough or groove into which the female fits and locks in. Females are slender and delicate, whereas males are much bigger and have a spiny trough or groove into which the female fits and locks in.

73. 8.9a and b

74. Schistosomiasis Once paired up the flukes travel from the liver to a permanent home that is species- specific. Once paired up the flukes travel from the liver to a permanent home that is species- specific. In Schistosoma mansoni it is near the large intestine, in S. haemotobium it is the bladder, and in S. nasale, a blood fluke of cows, it is the nose. In Schistosoma mansoni it is near the large intestine, in S. haemotobium it is the bladder, and in S. nasale, a blood fluke of cows, it is the nose.

75. Schistosomiasis Once established the pair remain in situ for the rest of their lives. Once established the pair remain in situ for the rest of their lives. The male consumes blood and feeds the female most of it, which she turns into eggs, which pass out of the host and can begin the life cycle again. The male consumes blood and feeds the female most of it, which she turns into eggs, which pass out of the host and can begin the life cycle again.

76. Schistosomiasis Causes an estimated 12,000-200,000 deaths annually. Causes an estimated 12,000-200,000 deaths annually. Causes anemia and malnutrition. Stunts growth and brain development in children. Causes anemia and malnutrition. Stunts growth and brain development in children. Liver damage, kidney failure, infertility and bladder cancer can result from infection. Liver damage, kidney failure, infertility and bladder cancer can result from infection.

77. Schistosomiasis Enlargement of the abdomen due to swelling of the liver is common. Enlargement of the abdomen due to swelling of the liver is common.

78. Carter Center schistosomiasis video https://www.youtube.com/watch?v=5O0k r7oW-6k https://www.youtube.com/watch?v=5O0k r7oW-6k https://www.youtube.com/watch?v=5O0k r7oW-6k https://www.youtube.com/watch?v=5O0k r7oW-6k

79. Do trematode parasites favor sex in hosts? Lively (1992) studied New Zealand freshwater snail. Host to parasitic trematodes. Lively (1992) studied New Zealand freshwater snail. Host to parasitic trematodes. Trematodes eat host’s gonads and castrate it which imposes strong selection pressure. Trematodes eat host’s gonads and castrate it which imposes strong selection pressure. Snail populations contain both obligate sexually and asexually reproducing females. Snail populations contain both obligate sexually and asexually reproducing females.

80. Do trematode parasites favor sex in hosts? Proportion of sexual vs asexual females varies from population to population. Proportion of sexual vs asexual females varies from population to population. Frequency of trematode infections varies also. Frequency of trematode infections varies also.

81. Do trematode parasites favor sex in hosts? If evolutionary arms race favors sex, then sexually reproducing snails should be commoner in populations with high rates of trematode infections. If evolutionary arms race favors sex, then sexually reproducing snails should be commoner in populations with high rates of trematode infections. Results match predictions. Results match predictions.

82. White slice indicates frequency of males and thus sexual reproduction

83. Frequency of males increases with increasing rates of trematode infection.

84. Class Monogenea The monogenetic flukes were previously classified as on order of the Trematoda, but recent work suggests they are more closely related to cestodes (tapeworms). The monogenetic flukes were previously classified as on order of the Trematoda, but recent work suggests they are more closely related to cestodes (tapeworms). Monogeneans are typically external parasites of fish that clamp onto the gills using a hooked organ called an opisthaptor. Some also parasitize frogs and turtles. Monogeneans are typically external parasites of fish that clamp onto the gills using a hooked organ called an opisthaptor. Some also parasitize frogs and turtles.

85. 8.11 Monogenean Fluke

86. http://www.bogleech.com/flatworms.html Attached monogeneans

87. Class Monogenea Unlike the trematodes, Monogeneans have only a single host. Unlike the trematodes, Monogeneans have only a single host. The egg hatches into a ciliated larva which seeks out its host in the water. The egg hatches into a ciliated larva which seeks out its host in the water. Attached to gills, adult feeds on mucus, epithelium and blood. Attached to gills, adult feeds on mucus, epithelium and blood.

88. Monogeneans attached to gills of goldfish https://www.youtube.com/watch?v=OiOez nXQZuI https://www.youtube.com/watch?v=OiOez nXQZuI https://www.youtube.com/watch?v=OiOez nXQZuI https://www.youtube.com/watch?v=OiOez nXQZuI

89. Class Cestoda (tapeworms) Tapeworms are parasites of the vertebrate digestive tract and about 4000 species are known. Tapeworms are parasites of the vertebrate digestive tract and about 4000 species are known. Almost all tapeworms require at least two hosts with the definitive host being a vertebrate, although intermediate hosts can be invertebrates. Almost all tapeworms require at least two hosts with the definitive host being a vertebrate, although intermediate hosts can be invertebrates.

90. Class Cestoda Members of the Class Cestoda (tapeworms) are quite different in appearance from the other members of the Platyhelminthes. Members of the Class Cestoda (tapeworms) are quite different in appearance from the other members of the Platyhelminthes. They have long, flat, tape-like bodies composed of a scolex for attaching to their host and a chain of many reproductive units or proglottids called strobila. New proglottids form behind the scolex and the strobila may become extremely long. They have long, flat, tape-like bodies composed of a scolex for attaching to their host and a chain of many reproductive units or proglottids called strobila. New proglottids form behind the scolex and the strobila may become extremely long.

91. 8.12

92. Tapeworm scolex The scolex is equipped with suckers and hooks that enable it to grip onto its host’s intestines. Hooks Suckers

93. Class Cestoda Tapeworms live in the intestines and because they are immersed in digested food lack a digestive system of their own. Instead they simply absorb food across their tegument. Tapeworms live in the intestines and because they are immersed in digested food lack a digestive system of their own. Instead they simply absorb food across their tegument.

94. Class Cestoda To facilitate the absorption of food a tapeworm’s tegument has huge numbers of tiny projections called microtriches, which are broadly similar to the microvilli of the vertebrate intestine. To facilitate the absorption of food a tapeworm’s tegument has huge numbers of tiny projections called microtriches, which are broadly similar to the microvilli of the vertebrate intestine. They similarly increase the surface area of the tegument for absorption. They similarly increase the surface area of the tegument for absorption.

95. 8.13

96. Class Cestoda Tapeworms are usually monoecious (have both male and female reproductive organs). Tapeworms are usually monoecious (have both male and female reproductive organs). A proglottid is fertilized by another proglottid in the same or a different strobila. A proglottid is fertilized by another proglottid in the same or a different strobila. Shell-encased embryos form in the uterus and exit the proglottid via a uterine pore or the entire proglottid may detatch and pass out of the host. Shell-encased embryos form in the uterus and exit the proglottid via a uterine pore or the entire proglottid may detatch and pass out of the host.

97. 8.14

98. Human tapeworms Humans are definitive hosts to several tapeworms including the beef tapeworm Taenia saginata, pork tapeworm T. solium, and fish tapeworm Diphyllobothrium latum. Humans are definitive hosts to several tapeworms including the beef tapeworm Taenia saginata, pork tapeworm T. solium, and fish tapeworm Diphyllobothrium latum.

99. Human tapeworms The lifecycles of these parasites are similar. The lifecycles of these parasites are similar. Shelled larvae are shed into the environment. Shelled larvae are shed into the environment. These are consumed by the intermediate host and the larvae (oncospheres) hatch, bury into blood vessels and make their way to skeletal muscle where they encyst becoming so called “bladder worms” or cysticerci. These are consumed by the intermediate host and the larvae (oncospheres) hatch, bury into blood vessels and make their way to skeletal muscle where they encyst becoming so called “bladder worms” or cysticerci.

100. Human tapeworms The encysted larva develops an invaginated scolex and waits, perhaps for years, for its host to be eaten. The encysted larva develops an invaginated scolex and waits, perhaps for years, for its host to be eaten. If the meat is uncooked the cysticercus extends its scolex, attaches to the wall of the intestine and within 2-3 weeks matures and begins growing and producing eggs. A tapeworm may be many meters long and live for years. If the meat is uncooked the cysticercus extends its scolex, attaches to the wall of the intestine and within 2-3 weeks matures and begins growing and producing eggs. A tapeworm may be many meters long and live for years.

101. 8.15

102. Humans as intermediate hosts Humans may become intermediate hosts for tapeworms with potentially disastrous consequences if they consume shelled larvae in contaminated food. Humans may become intermediate hosts for tapeworms with potentially disastrous consequences if they consume shelled larvae in contaminated food. In an evolutionarily unfamiliar environment, cysticerci may encyst in inappropriate locations such as the brain, which is frequently fatal. In an evolutionarily unfamiliar environment, cysticerci may encyst in inappropriate locations such as the brain, which is frequently fatal.

103. 8.16 Cysticerci in human brain

104. Tapeworm manipulations of hosts Continuing the theme of parasite manipulations we’ve seen this semester it’s not surprising that some tapeworms also manipulate their hosts to ensure they can complete their lifecycles. Continuing the theme of parasite manipulations we’ve seen this semester it’s not surprising that some tapeworms also manipulate their hosts to ensure they can complete their lifecycles. A good example is the tape worm Hymenolepis diminuta, which parasitizes rats and flour beetles. A good example is the tape worm Hymenolepis diminuta, which parasitizes rats and flour beetles.

105. Tapeworm manipulations of hosts Adults live in the bowels of rats (where they can grow to 45 cm in length) and produce eggs which pass out of the gut in rat droppings. Adults live in the bowels of rats (where they can grow to 45 cm in length) and produce eggs which pass out of the gut in rat droppings. Beetles are attracted to and eat rat droppings that contain tapeworm eggs by an apparently highly attractive scent. Beetles are attracted to and eat rat droppings that contain tapeworm eggs by an apparently highly attractive scent.

106. Tapeworm manipulations of hosts Not clear whether the eggs, adult tapeworms, or rat host produce this scent, but beetles strongly prefer egg-containing feces to those that are egg free. Not clear whether the eggs, adult tapeworms, or rat host produce this scent, but beetles strongly prefer egg-containing feces to those that are egg free. Once in the beetle the tapeworm produces several chemicals that sterilize female beetles by blocking the flow of nutrients that allows egg formation. Once in the beetle the tapeworm produces several chemicals that sterilize female beetles by blocking the flow of nutrients that allows egg formation.

107. Tapeworm manipulations of hosts In order to reach its final host the tapeworm needs to ensure that the beetle gets eaten by the definitive host, a rat. In order to reach its final host the tapeworm needs to ensure that the beetle gets eaten by the definitive host, a rat. The tapeworm produces chemicals, which make the beetle less likely to conceal itself as well as sluggish and slow to escape if attacked. The tapeworm produces chemicals, which make the beetle less likely to conceal itself as well as sluggish and slow to escape if attacked.

108. Tapeworm manipulations of hosts As a final trick the tapeworm also inactivates the beetle’s last line of defense. As a final trick the tapeworm also inactivates the beetle’s last line of defense. Flour beetles have glands in the abdomen that spray a foul-tasting liquid, which often will cause a rat to spit out a beetle it has started to eat. Flour beetles have glands in the abdomen that spray a foul-tasting liquid, which often will cause a rat to spit out a beetle it has started to eat. The tapeworm blocks the gland that makes this chemical, so that the beetle doesn’t taste bad to the rat and is consumed. The tapeworm blocks the gland that makes this chemical, so that the beetle doesn’t taste bad to the rat and is consumed.

109. Ectoprocta Brachiopoda Phoronida Lophophorata Lophotrochozoa Rotifera Acanthocephala Platyhelminthes Annelida Sipuncula Entoprocta Nemertea Mollusca Parenchymia

110. Phylum Nemertea (Rhynchocoela) Ribbonworms The nemerteans (ribbon worms) are long, marine, predatory worms and there are about 1000 species known. The nemerteans (ribbon worms) are long, marine, predatory worms and there are about 1000 species known. Most are less than 20cm in length, but others are many meters in length. Most are less than 20cm in length, but others are many meters in length.

111. http://farm3.static.flickr.com/2177/2169551899_0667313f6c.jpg Giant Nemertean Longest known in phylum Up to 30 meters long Britain and Ireland Shallow waters, pools and mud 10 – 20 eyes http://www.marlin.ac.uk/images/distribution_maps/uklinlon.jpg

112. 8.19 Baseodiscus mexicanus a nemertean from the Galapagos Islands

113. Phylum Nemertea (Rhynchocoela) Ribbonworms The general body plan of nemerteans is similar to that of turbellarians. The general body plan of nemerteans is similar to that of turbellarians. Like turbellarians they have a ciliated epidermis and possess a large number of gland cells. They also have flame cells. Like turbellarians they have a ciliated epidermis and possess a large number of gland cells. They also have flame cells.

114. Phylum Nemertea (Rhynchocoela) Ribbonworms Unlike members of the Platyhelminthes nemerteans have a complete gut with a mouth and anus Unlike members of the Platyhelminthes nemerteans have a complete gut with a mouth and anus Also possess a true closed circulatory system. There are blood vessels, but no heart. Instead valves and muscles control blood flow. Also possess a true closed circulatory system. There are blood vessels, but no heart. Instead valves and muscles control blood flow.

115. Phylum Nemertea (Rhynchocoela) Ribbonworms The flame cells are associated with the circulatory system and so are used to eliminate metabolic wastes (excretion) rather than just being used for osmoregulation as in Platyhelminthes. The flame cells are associated with the circulatory system and so are used to eliminate metabolic wastes (excretion) rather than just being used for osmoregulation as in Platyhelminthes.

116. http://www.dnr.sc.gov/marine/sertc/images/photo%20gallery/nemertean.jpg

117. Phylum Nemertea (Rhynchocoela) Ribbonworms Prey is captured using a long muscular proboscis armed with a barb called a stylet. Prey is captured using a long muscular proboscis armed with a barb called a stylet. The proboscis lies in a body cavity called the rhynchocoel and muscular pressure on fluid in the rhynchocoel causes the proboscis to be quickly everted. The rhynchocoel appears to be a modified coelom. The proboscis lies in a body cavity called the rhynchocoel and muscular pressure on fluid in the rhynchocoel causes the proboscis to be quickly everted. The rhynchocoel appears to be a modified coelom. The prey is wrapped in the sticky, slime-covered, proboscis and stabbed repeatedly with the stylet. Neurotoxins in the slime incapacitate the prey. The prey is wrapped in the sticky, slime-covered, proboscis and stabbed repeatedly with the stylet. Neurotoxins in the slime incapacitate the prey.

118. 8.18 Internal structure of female ribbon worm (above). Nemertean with proboscis extended (right)

119. Phylum Nemertea (Rhynchocoela) Ribbonworms Feed on: Small invertebrates (crustaceans, nematodes, polychaetes, larvae, etc). Invertebrate eggs. Feed on: Small invertebrates (crustaceans, nematodes, polychaetes, larvae, etc). Invertebrate eggs. http://www.youtube.com/watch?v=EwcEY AGu07E http://www.youtube.com/watch?v=EwcEY AGu07E http://www.youtube.com/watch?v=EwcEY AGu07E http://www.youtube.com/watch?v=EwcEY AGu07E