Worms  Flatworms – Phylum Platyhelminthes  Roundworms – Phylum Nematoda  Segmented worms – Phylum Annelida

Flatworms (Phylum Platyhelminthes)

Planarian worm

Tapeworm head

 Each segment a complete reproduction kit testes and ovaries  Absorbs nutrients from juices in gut  Makes millions of eggs a day.  Adds segments to tail end….

Tapeworms in humans can grow more than 33 ft. long….

Tapeworm life cycle

Roundworms (Phylum Nematoda)  Among most numerous of all animals.  Rotting apple can contain as many as 90,000 roundworms.  Cubic meter of garden soil can contain more than 1,000,000 nematodes.

Roundworm anatomy

Trichinella worm

Filarial roundworms can cause elephantiasis  Transmitted by biting insects, esp. mosquitoes.  Block passage of fluids in lymph vessels, causing inflammation

Ascaris worm  Parasitic nematode that infects pigs and people.  Typically found in tropical and sub-tropical areas with poor sanitation.  Largest intestinal roundworm, and most common worm infection for humans worldwide.  Infestation can cause morbidity, sometimes death by blocking digestive system.

Ascaris life cycle 1.Adult worms live in small intestine. 2.Eggs passed through feces (200,000/day). 3.Fertilized eggs develop into embryos. 4.Eggs swallowed via unclean food or fingers. 5.Larvae hatch, travel through blood to lungs. 6.Larvae mature in lungs, climb/coughed into throat, where swallowed. Pass into small intestine.

Ascaris-filled intestine

Segmented worms (Phylum Annelida)  “annelus” = little ring  Worms with bodies divided into segments.  Most segments similar, but may be modified to perform special functions – eyes, antennae, appendages, etc.

Leeches  External parasites that suck blood from hosts.  Powerful suckers help cling to hosts. Some have sharp jaws to cut through skin.  Some anesthetize skin so host doesn’t feel bite!

Medicinal leeches  Commonly used in Middle Ages for bloodletting (draining blood to cure illnesses).  Used in modern medicine to reduce swelling after surgeries.

 Giant Palouse Earthworm lives in Eastern WA and Idaho.  Can grow up to 3 feet long!

Earthworm Anatomy

How do earthworms do “the nasty”?  Earthworms are hermaphroditic (have both male and female reproductive organs)  Two worms attach to each other and exchange sperm, then separate.  Each worm excrete eggs onto skin near clitellum, which secretes thick band of mucous.  Worm slips out of mucous band, which hardens until fertilized eggs hatch.

The End (Thank G-d!!) Let’s all go home and forget this ever happened…..