WORMS

•Platyhelminthes

•Nematodes

•Annelids

Annelids

WORMS

•Platyhelminthes

•Nematodes

•Annelids

Annelids

NematodesWhat must I learn?

• Round worms: Cylindrical and soft body with tapered end, not divided in segments.

• Most of them are free-living but some are parasitic and responsible for many diseases. (Pinworm, anisakis, trichina)

• No respiratory system.

Nematodes

• Pinworms– Adults reside in the large intestine.– Enter humans by being eaten.

• Dracunculus• Hookworms

– Adults live in the small intestine of humans.– Enter host through the skin, usually between the toes. That makes you want to

walk around barefoot, doesn’t it?

• Anisakis• Trichina

– Live in humans & other omnivores (like piggys)– Adults live in the small intestine of it’s host; larvae encyst in the stomach and

skeletal tissue (ouch!). Enter host by being eaten.

• Picture of a male nematode.

M O V E M E N T

•No circular muscle in body walls

•Longitudinal muscle flexion combined with

high internal fluid pressure produces whip-

like wriggle

WORMS

•Plathyelminthes

•Nematodes

•Annelids

Annelids

Annelid Characteristics• The phylum includes

polychaetes, earthworms (Oligochaetes), and leeches.

• Cutaneous respiration in terrestrial and branchial respiration in marine.

True segmented worms• Metameric

segmentation

Polychaete

What do Oligochaetes look like?

Freshwater, very few marine and most terrestrial.

No parapodia.

Clitellum functions in reproduction.

How do Oligochaetes reproduce and develop?

Sexual

Mutual cross-fertilization.

Cocoon formed by clitellum.

Earthworm gathering

Class Hirudinea (Leeches)

• Predominately freshwater, but do occur in all seas and moist soil

• Leeches do not burrow or crawl, lack parapods and setae

• Feed on blood

Leech