Phylum Annelida The Segmented Worms Class Polychaeta – feather dusters Class Clitellata Subclass Oligochaeta – earthworms Subclass Hirudinea – leeches Class Echiura – spoon worms

Annelus: Lt.“ring”, as in “annuli” of trees/reptile bones/clam shells Cephalization! Well-developed nervous system: nerve cord with ganglion in each segment and anterior brain Bilaterally symmetrical Organs within a true coelom (cavity within mesoderm) Compartmentalization of organs / movement of parts of body Closed circulatory system with five pairs of “aortic arches”

Sophisticated digestive system: mouth – food enters pharynx – passes through esophagus – peristalsis crop – storage gizzard – grinding intestine – more digestion anus – waste exits

Earthworm anatomy Intestine Gizzard Esophogus Crop Pharynx Mouth

Appendages: Setae &/or parapodia Nephridia remove nitrogenous wastes; wets skin No lungs - use diffusion, some have simple gills Most have red hemoglobin in blood (very efficient)

Most are hermaphroditic testes in 10th and 11th ovaries in 13th with seminal vesicles and receptacles for sperm storage Clitellum produces “slime band” protective coat around eggs

Major Classes of Annelids Class Polychaeta (“many hairs”) (~12,000 species): bristleworms, tube worms, featherdusters marine worms with parapodia and (most) jaws! Class Clitellata (~10,000 species) Subclass Oligochaeta (means “long hair”): 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 Subclass Hirudinea (Latin: hirudo = leech): terrestrial / aquatic leeches some parasitic, some free-living medicinal anticoagulant “hirudin”

An aquatic oligochaete host of whirling disease

Class Polychaeta

A filter-feeding polychaete: feather-duster

The Bobbit Worm (polychaete)

Bristle-worm (nereis, polychaete)

Nereis closeup

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

Fanworm

Class Hirudinea 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.).

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

Spoon Worms: Class Echiura