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“Radiata” Deuterostomia Protostomia

Bilateria

Eumetazoa

Metazoa

Ancestral colonialflagellate

Phylum: Platyhelminthes

Kingdom: AnimaliaPhylum: Platyhelminthes

Class: Turbellaria

Class: Trematoda

Class: Cestoda

free-living planaria

parasitic tapeworms

parasitic flukes

•flatworms•most primitive animal that has/is...

•bilateral symmetry•dorsal/ventral; anterior/posterior; left/right

•triploblastic•endoderm- forms digestive system•ectoderm- forms outer covering, nervous system•mesoderm- forms muscle, excretory, reproductive systems

•true organs•several tissues function together as organ•evolutionary step above Cnidarians

Phylum: PlatyhelminthesGeneral information

•the first hunter•aided by...

•bilateral symmetry•cephalization

•paired sense organs at the head

•acoelemate•mesoderm present•but no true body cavity (i.e. has a “solid body”)•only internal cavity is the gut


•acoelemate•no body cavity (i.e. “solid body”)


•circulatory & respiratory systems•none•thin, flat bodies allow diffusion of nutrients and gases

•nervous system•centralized nervous system•cephalization

•brain and sensory organs at head•2 nerve cords run length of body

•digestive system•free-living planaria

•highly branched with single opening•parasitic tapeworm

•none


•reproductive system•sexual

•hermaphrodites•testes & ovaries, uterus in mesoderm layer•cross- or self-fertilization depending on species

•asexual•binary fission•fragmentation and regeneration


Kingdom: AnimaliaPhylum: Platyhelminthes

Class: Turbellaria

Class: Trematoda

Class: Cestoda

free-living planaria

parasitic tapeworms

parasitic flukes

Phylum: PlatyhelminthesClass: Turbellaria

•free-living flatworms•may have ciliate as ancestor•size range from <1-60 cm (FYI)•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

•nervous system•cerebral ganglia is simple brain•sensory cells

•statocysts sense gravity•light sensory cells at eyespots•chemosensory cells in auricles

•2 ventral nerve cords connected by transverse nerve cords run length of body

•protonephridia is simple excretory system•flame cells are ciliated and move fluid through branched ducts to outside via excretory pores•maintains osmotic balance


auricle

eyespot

•digestive system•branching provides high surface area for diffusion of nutrients

•2-way digestive tract (mouth=anus)

•mouth, muscular pharynx, gastrovascular cavity, intestine•digestion extracellular & intracellular

•digestive enzymes secreted into gastrovascular cavity•small food particles enter ameboid cells by phagocytosis and digested in food vacuoles



Reproduction•asexual by binary fission•sexual- hermaphrodites•cross-fertilization•some mate by “penis-fencing”•sperm injected in body wall•fertilization & early development inside “mother”•juveniles that resemble adult released


Overview of organ systems•digestive•nervous•reproductive•excretory

Phylum: PlatyhelminthesClass: TurbellariaFYI

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: PlatyhelminthesClasses: Cestoda, Trematoda “The parasitic flatworms”

•most have 2 or more hosts during life cycle•intermediate host(s)- 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

•tegument- special epidermis•protects against detection/digestion by host •some w/ microvilli to aid absorption of host nutrients•some secrete their own digestive/protective enzymes

Phylum: PlatyhelminthesClass: Trematoda

•parasitic flukes•live in intestine, liver, lungs, bladder and blood vessels•reproduction

•asexual in early life stages•sexual in adult stages producing large numbers of eggs stored in uterus

Phylum: PlatyhelminthesClass: TrematodaGenus: Schistosoma

•causes chronic human disease schistosomiasis

•major world health problem •common in Africa, Asia, South America•acute symptoms

•fever, rash, body pains, cough, dysentery

•long term symptoms•organ damage; lesions in CNS

•hosts-•intermediate- aquatic snail•definitive- human (or other vertebrates)

cercaria

adult

miracidia

Phylum: PlatyhelminthesClass: Trematoda

Genus: Schistosoma

Life cycle stages:•fertilized 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/fertilize more eggs

Phylum: PlatyhelminthesClass: TrematodaChinese 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: PlatyhelminthesClass: TrematodaLiver flukes

Phylum: PlatyhelminthesClass: Cestoda

•tapeworms•parasitic•as long as 100 feet•most have at least 2 hosts•no digestive system; nutrients absorbed from host•scolex = specialized head w/ sucker discs & hooks for anchoring to host

•long flat body •made of many proglottids

•complete reproductive units•male & female gonads•conveyor belt-like

•youngest behind head•oldest w/ eggs at end•old ones shed in host feces

•reproductive output high

Phylum: PlatyhelminthesClass: Cestoda (tapeworms)

Beef tapewor

m life cycle


Phylum: PlatyhelminthesClass: Cestoda•Beef tapeworm life cycle

•cattle ingest human feces with eggs•egg covering digested in cow’s stomach to release larva with scolex that bores through intestinal wall to blood vessel to muscle•larva grows in muscle to form a cyst•human eats undercooked meat with cysts•cyst digested open releasing tapeworm•worm attaches to intestinal wall via scolex and tapeworm grows, makes new eggs that are released in human feces


•Pork tapeworm•similar to beef tapeworm but pig is intermediate host

•Broad fish tapeworm •eggs released from definitive host reach freshwater to produce free swimming larva•larva eaten by copepods (small crustaceans)•copepods eaten by fish•larva bore into fish muscle and form cysts•humans get by eating raw/undercooked fish

Platyhelminthes- The Table

•Symmetry- bilateral•Segmentation- N/A•Mesoderm present- yes, triploblastic •Determinant cleavage•Type of body cavity- acoelomate, “solid body”•Ciliated larva- trocophore-like in some (free-swimming, ciliated)•Protostome- N/A; mouth=anus•Nervous system- simple brain (ganglia) at head, 2 nerve cords run length of body, specialized sensory cells•Respiratory system- none, flat, thin body for gas exchange by diffusion

•Digestive system- •Turbellaria-highly branched, 2-way•Trematoda- has some•Cestoda- none, absorbs food from host digestive tract via diffusion

•Excretory system- protonephridia: ciliated flame cells push wastes through excretory ducts & out excretory pores

•Reproductive system- have testes and uterus; planaria are hermaphrodites and reproduce sexually or asexually (binary fission or fragmentation/regeneration)


•Circulatory system- none; flat, thin body allows gas exchange by simple diffusion

•Members- •Most parasitic

•Cestoda (tapeworms)•Trematoda (flukes)

•Turbellaria- free-living, non-parasitic


poriferacnidaria ctenophora phoronida ectoprocta brachiopoda echinodermata chordata platyhelminthes...

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