Worm Phyla:Worm Phyla: Platyhelminthes Platyhelminthes (flatworms - (flatworms -

acoelomates)acoelomates)

Nematoda Nematoda (roundworms - (roundworms - pseudocoelomates)pseudocoelomates)

Annelida Annelida (segmented worms – coelomates)(segmented worms – coelomates)

Phylum #1 Phylum #1

PlatyhelminthesPlatyhelminthes(flatworms)(flatworms)

Classes:

1. Turbellaria (free-living)

2. Trematoda (parasitic)

3. Cestoda (parasitic)

Phylum Platyhelminthes ("flatworms")

Evolved from Cnidarians, gained bilateral symmetry and developed excretory, nervous and reproductive systems. Bilateral, acoelomates. Digestion = single opening (mouth and pharnyx) and digestive cavity. Excretory = flame cells excrete wastes. No circulatory or respiratory systems; diffusion only for O2 / CO2 exchange. Sexual (hermaphrodites) and asexual reproduction regeneration.

Class #1Class #1

TurbellariaTurbellaria(Phylum Platyhelminthes)(Phylum Platyhelminthes)

free-living scavengers branched intestines with pharynx tube eyespots, can learn (chopped up & fed to others...) hermaphroditic; sexually reproduce

A variety of marine

turbellarians

Eurylepta

This turbellarian flatworm mimics a (very unsavory) sea slug

Marine Flatworms mating

Class #2Class #2 Trematoda - Trematoda -

flukesflukes (Still Phylum (Still Phylum

Platyhelminthes)Platyhelminthes) Parasitic (species-specific) Thick, protective "tegument" resists acids/enzymes No digestive system (diffusion only for gases / food) no eyespots; very little cephalization

Ex: Swimmer's itch, Schistosoma, Liver flukes

Sheep liver fluke

Sheep livers with trematode fluke

Schistosoma male/female

Schistosoma

male / female

blood flukes

Typical Schistosoma eggSchistosome eggs, which may become lodged within

the hosts intestinal wall or in liver, are the major cause of pathology in schistosomiasis.

Class # 3Class # 3

CestodaCestoda ((tapewormstapeworms)) (still Phylum Platyhelminthes)(still Phylum Platyhelminthes)

• parasites (mostly mild symptoms in well-nourished people)

scolex (head with hooks) proglottids (egg cases)

Ex: Diplydium (cat intestines feces larval fleas adult fleas another cat ingested by licking fur)

Scolex of tapeworm

Nereis closeup

Methane hydrate deposits on the ocean floor teem with Methane hydrate deposits on the ocean floor teem with life. Residents include ferocious polychaete ice worms life. Residents include ferocious polychaete ice worms that burrow into the formations and defend their lairs that burrow into the formations and defend their lairs

against intruders.against intruders.

Tapeworm (Class Cestoda)

•Scolex and proglottids

PhylumPhylum Nematodes Nematodes (roundworms)(roundworms) Evolution- gained body cavity Evolution- gained body cavity (pseudocoelom), separate sexes, (pseudocoelom), separate sexes, and complete digestive system (2 and complete digestive system (2 openings). Bilateral symmetry. openings). Bilateral symmetry. Dioeciuos– not hermaphrodites. Dioeciuos– not hermaphrodites. Complete digestive system (two Complete digestive system (two openings). Circulation and openings). Circulation and respiration through diffusion.respiration through diffusion.

Nematodes are pseudocoelomates

DISEASESPinworm (Enterobius sp.): eggs swallowed (dust/food) lg. intestine (lay eggs) anus (itching)

Lungworm (Ascaris sp.): eggs swallowed penetrate to lungs throat swallowed intestine (lay eggs)

Trichinosis: cysts ingested (pork, bear) intestine (pain, diarrhea, fever) blood muscles (lumps, pain)

Hookworm (Huck Finn disease): bloodstream push abdomen through intestine eggs outside

Brainworms, heartworms, Guinea worms (“the fiery serpent” makes great tattoos!), Filaria (clog lymph: elephantiasis), Loa loa (eyeworms)

The Fiery Serpent- Guinea Worm

Trichina-- a roundworm (nematode) common in pork• picture shows capsule embedded in muscle tissue.

• enters host via raw or poorly cooked meat

• eggs shed in the gastrointestinal tract--> feces

• eggs eaten by herbivores --> encyst in muscle

• encysted worm is resistant to antihelmithic drugs.

Heartworm-- a parasitic nematode

Pinworms-- infections of kids (itchy eggs!)

Reminder: Kingdom Animalia; Phylum Nematoda

Phylum Annelida Phylum Annelida The The Segmented WormsSegmented Worms

Evolution-development of coelom.Cephalization! Well-developed nervous system: nerve cord with ganglion in each segment and anterior brain Bilaterally symmetricalOrgans within a true coelom (cavity within mesoderm)Compartmentalization of organs / movement of parts of bodyClosed circulatory system with five pairs of “aortic arches”Most have red hemoglobin in blood (efficient) Sophisticated digestive system:

mouth pharynx esophagus crop gizzard intestine anus

Appendages: Setae &/or parapodiaExcretion- Nephridia remove nitrogenous wastes; wets skinRespiration—use diffusionMost hermaphroditic, some dioecious.

Classes of Annelids

Oligochaeta: earthworms, nightcrawlers, (aquatic) tubifex worms

20-45 tons of soil/year/acre processed by worms on organic farms each worm processes its own weight each day

Polychaeta: bristleworms, tube worms, featherdusters

marine worms with parapodia and (most) jaws!

Hirudinea: terrestrial / aquatic leeches

some parasitic, some free-living•medicinal anticoagulant “hirudin”

Fanworm

A filter-feeding A filter-feeding polychaete: feather-polychaete: feather-

dusterduster

Bristle-worm (nereis)

The medicinal leech is best known as the organism used for blood letting (people used to believe many health problems caused by "bad" blood). They are being used once again to remove blood from hematomas (areas of blood leakage) resulting from surgery (like re-attaching severed limbs, etc.).

http://www.sp.uconn.edu/~mcbstaff/graf/AvHm/MedUsemain.htm