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“Radiata” Metazoa Ancestral colonial flagellate Deuterostomia Eumetazoa Protostomia Bilateria Phylum: Platyhelminthes Nematoda Nemertea Rotifera Arthropoda Annelida Mollusca Platyhelminthes Chordata Echinodermata Brachiopoda Ectoprocta Phoronida Ctenophora Cnidaria Porifera Kingdom: Animalia Phylum: Platyhelminthes Class: Trematoda parasitic flukes Class: Cestoda parasitic tapeworms Class: Turbellaria free-living planaria Phylum: Platyhelminthes •flatworms •most primitive animal that has/is... •bilateral symmetry •dorsal/ventral; anterior/posterior; left/right •triploblastic •endoderm- digestive system •ectoderm- outer covering, nervous system •mesoderm- muscle, excretory, reproductive systems •tissue level of organization •true organs •believed to be first animal that could hunt for food; aided by bilateral symmetry and paired sense organs at the head •acoelemate •no body cavity (i.e. “solid body”) •only internal cavity is the gut Phylum: Platyhelminthes •acoelemate •no body cavity (i.e. “solid body”) •only internal cavity is the gut Phylum: Platyhelminthes •no organized circulatory or respiratory systems •thin,flat bodies allow diffusion of nutrients and gases •centralized nervous system (cephalization) •brain and sensory organs at head •2 nerve cords run length of body •digestive system •free-living planaria has branched one; single opening •parasitic tapeworm has none •reproductive system •sexual- hermaphrodites •both testes and ovaries, uterus in mesoderm layer •cross- or self-fertilization •asexual •binary fission •fragmentation and regeneration Phylum: Platyhelminthes Class: Turbellaria •free-living flatworms •may have ciliate as ancestor •size range from <1-60 cm •locomotion •layers of muscles •cilia •some have glands that secrete mucus to glide along •most are carnivorous, scavengers •habitat •most marine or freshwater •some on humid land Phylum: Platyhelminthes Class: Turbellaria •well-defined nervous system w/ sense organs •ganglia concentrated as simple brain at head •sensory cells (statocysts sense gravity, light sensory cells at eyespots, chemosensory cells) •2 nerve cords run length of body •simple excretory system- protonephridia •consists of flame cells (specialized ciliated cells) •move fluid through branched ducts to outside via excretory pores •maintains osmotic balance Phylum: Platyhelminthes Class: Turbellaria •digestive system (2-way system) •branched w/ single opening serving as mouth/anus •mouth, muscular pharynx, intestine •digestion is extracellular and intracellular •digestive enzymes secreted into digestive cavity •small food particles enter ameboid cells by phagocytosis and digested in food vacuoles Phylum: Platyhelminthes Class: Turbellaria Reproduction •asexual by binary fission •sexual- hermaphrodites •cross-fertilization •some mate by “penis-fencing” •sperm injected in body wall •fertilization and early development inside “mother” •juveniles that resemble adult released Phylum: Platyhelminthes Class: Turbellaria organ systems •digestive •nervous •reproductive •excretory Phylum: Platyhelminthes Class: Turbellaria Convoluta roscoffensis •mutualistic relationship •ingests photosynthetic flagellates •flagellates lose flagella and cell wall and take up residence in worm gut •as adult, worm no longer feeds and survives off of flagellates •later in life, worm digests flagellates and all die Phylum: Platyhelminthes Class: Turbellaria Genus: Bdelloura •commensalism with horseshoe crab •attaches to gills or appendages of horseshoe crab •worm gets transportation, shelter, food scraps Phylum: Platyhelminthes Classes: Cestoda, Trematoda ”The parasitic flatworms” •most have 2 or more hosts during life cycle •intermediate host- juvenile stage •definitive host- adult stage •much of structure devoted to reproduction •produce lots of offspring to make it to the next host •do not survive long outside of host •contain unusual epidermis called tegument •protects against detection/digestion by host •some have microvilli to aid absorption of host nutrients •some syncytial (cells have continuous cytoplasm) to aid in distribution of nutrients •some secrete their own digestive/protective enzymes Phylum: Platyhelminthes Class: Trematoda •parasitic flukes •live in intestine, liver, lungs, bladder and blood vessels •involve at least 2 hosts •reproduction •asexual in early life stages •sexual in adult stages producing large numbers of eggs stored in uterus Phylum: Platyhelminthes Class: Trematoda Genus: Schistosoma •causes human disease schistosomiasis •major world health problem •common in Africa, Asia and South America •chronic disease •acute symptoms: fever, rash, body pains, cough, dysentery •long term: can cause organ damage; rare lesions in central nervous system •hosts•intermediate is aquatic snail •definitive is human (or other vertebrates) cercaria adult Phylum: Platyhelminthes Class: Trematoda Genus: Schistosoma Life cycle stages: •eggs hatch into miracidium (larval stage, swimming ciliate, can only live 24 hrs outside of host) •miracidium enters snail and becomes sporocyst (loses cilia) •sporocyst reproduces asexually to produce more sporocyst or redia •redia becomes cercaria (swimming stage that resembles adult form) •cercaria leaves first host and enters vertebrate host (release digestive enzymes to help bore through skin) •once in host, cercaria migrates through blood to large intestine and becomes adult to produce more eggs Phylum: Platyhelminthes Class: Trematoda Chinese liver fluke Hosts: snail>fish>mammal (human) In definitive host... •cysts digested in intestine releasing fluke •fluke travels up bile duct to liver •attaches with suckers and feeds on blood •causes anemia and liver disease •may block bile duct Phylum: Platyhelminthes Class: Trematoda Liver flukes Phylum: Platyhelminthes Class: Cestoda •tapeworms •parasitic •as long as 100 feet •most have at least 2 hosts •no digestive system; nutrients absorbed from host •scolex = specialized head that has sucker discs and hooks for anchoring to host Phylum: Platyhelminthes Class: Cestoda •long flat body made of many units called proglottids •proglottid = complete reproductive unit with male and female gonads •youngest proglottid behind head •older proglottids w/ eggs shed in feces of definitive host •reproductive output high •many proglottids per tapeworm •many eggs per proglottid Phylum: Platyhelminthes Class: Cestoda Beef tapeworm life cycle Phylum: Platyhelminthes Class: Cestoda •Beef tapeworm life cycle (Taenia saginata) •cattle ingest human feces with eggs and egg covering digested off to reveal larva with scolex that bores through intestinal wall to blood vessel to muscle •larva grows in muscle to form a cyst called “bladder” •human eats undercooked meat with “bladder” •cyst digested open releasing tapeworm •scolex attaches to intestinal wall and tapeworm grows, makes new eggs Phylum: Platyhelminthes Class: Cestoda •Pork tapeworm •similar to beef tapeworm but pig is intermediate host •can also develop bladders in human host •can grow in eye or brain (interfere with vision or cause seizures •Broad fish tapeworm (Diphyllobothrium latum) •eggs reach freshwater to produce free swimming larva •eaten by copepods (small crustaceans) •copepods then eaten by fish •humans can get by eating raw or undercooked fish •absorb vitamin B-12 and can cause megaloblastic anemia Platyhelminthes- The Table •Symmetry- bilateral •Segmentation- N/A •Mesoderm present- yes, triploblastic •Determinant cleavage •Type of body cavity- acoelomate, “solid body”, lack body cavity other than digestive cavity •Ciliated larva- trocophore-like in some (freeswimming, ciliated) •Protostome- N/A; mouth=anus •Nervous system- cerebral ganglia form simple brain, 2 nerve cords, specialized sensory cells •Respiratory system- none, flat and thin for respiration by diffusion across cell membranes Platyhelminthes- The Table •Digestive system- Turbellaria has highly branched one but still 2-way (mouth=anus); Trematoda has some digestive tract; Cestoda has no digestive tract, absorbs food through external surface •Excretory system- Excrete using ciliated flame cells that push wastes through excretory ducts and out excretory pores •Reproductive system- contain testes and uterus; planaria are hermaphrodites; can reproduce by binary fission and fragmentation/regeneration Platyhelminthes- The Table •Circulatory system- none; relies on flat thin body for diffusion across cell membranes •Members- Most are parasitic including Cestoda (tapeworms) and Trematoda (flukes). Turbellaria are free-moving and not parasitic.