Phylum Annelida

Segmented Worms

Earthworm

Pinworm (a roundworm)

• Common human intestinal parasite• Eggs transmitted through contaminated food, hands, or

commonly, water • Symptom – itching in anal area• A nuisance rather than serious disease• No association with socioeconomic level, race or culture• Treatment – drugs kill the adult pinworm - and not the

egg so treatment for 2 weeks• Prevention – dependent on personal hygiene and

cleanliness of the living quarters

Pinworm

Ascaris

• Parasitic nematode (Roundworm)• Affects humans in sub-tropical areas with poor

sanitation• Symptoms – cough, low-grade fever, vomiting

worms, worms in stool, gallstones, pancreatis• Prevention – proper disposal of feces and

proper washing of food• Treatment – drugs target the cells of the worm

Ascaris

Hookworm

• Parasitic nematode (roundworm) lives in small intestine of host (mammals – dogs, cats, humans)

• Much smaller than Ascaris• Leading cause of death in developing

countries of tropics and subtropics• In children cause cognitive and growth

retardation, prematurity, and low birth weight

Hookworm

• No symptoms or signs

• Intestinal inflammation

• Larval invasion of the skin could cause itching

• Coughing, chest pain, wheezing, fever

• Nausea, vomiting, constipation, diarrhea in later stages

Hookworm

• Larvae survive in damp dirt (sandy soil)

• Cannot survive in clay or muck

• Do not defecate in places other than toilets

• Keep raw sewage away from agriculture

• Do not walk barefoot in infected areas

• Deworm pet dogs

Hookworm

Trichinella

• Parasitic nematode (roundworm)

• Can infect humans, swine, horses, wild animals– Swine – get it from feeding them waste

products contaminated, exposure to rodents, cannibalism within an infected herd

• In humans, larvae invade muscle tissue

• Fever, muscle pain

Trichinella

Characteristics of Annelids

• Earthworms are the most highly developed worms.

• They are divided into segments or parts.

• They are found in salt and fresh water as well as in the soil.

Characteristics of Annelids

• Earthworms are helpful to man as bait for fishing and more importantly, because they loosen the soil for roots to grow.

• There are 2700 species of earthworms. 

• An earthworm is generally earthtones such as brown, tan, etc. It can be up to eight feet in length!

Body Cavity• Coelomate

Muscular-Skeletal

• A earthworm does not have a skeleton. It has bristles on each segment called setae that help the earthworm move.

• Rear Anchor→ Elongation → Front Anchor→ Pull

Muscular-Skeletal

• The earthworm has two sets of muscles; one that makes it long and thin and one that makes it shorter and fatter.

Digestion• A earthworm has a digestive system. It

eats dirt, digesting the plant and animal matter in the dirt and then eliminates the rest.

• a pharynx for the food to go down,

• a crop to store the food in,

• a gizzard that grinds the food down,

• intestines for the food to pass through and take out nutrients

• an anus for the food to come out.

Digestion (cont.)

• Virtual Worm – Digestion

• worm systems

Nervous System• A earthworm

has a

nervous system

with a simple

brain and

ventral nerve

cord.

Circulation• A earthworm has blood and blood

vessels with multiple (5) hearts.

Respiration

• A earthworm has no respiratory organ. It takes in oxygen directly through its skin and gives off carbon dioxide. Its skin is always moist.

Reproduction

• A earthworm has both sperm and eggs within its body and reproduces sexually. However, the eggs must be fertilized by the sperm of another worm.

Reproduction (cont.)• Earthworms are hermaphrodites with

complex male and female reproductive organs present in each individual, but they cross fertilize. 

• Two earthworms mate by attaching at their clitella and exchanging sperm, and then they separate. 

Reproduction (cont.)• The received sperm are temporarily stored

in sperm receptacles while the clitellum secretes a mucous cocoon. 

• The cocoon slides along the worm, picking up the eggs which are produced in ovaries and then the stored sperm from special reproductive pores and then slips off the worm's head.

• The embryos develop within the cocoon.

Mating of 2 Earthworms

Reproduction

Excretion

• A earthworm's wastes help to fertilize the soil. It gets rid of its wastes through tubes called nephridia that lead to pores that allow the wastes out.

Symmetry

• A earthworm has bilateral symmetry.

Helpful Earthworms!

• Did you know that Earthworms are a gardeners

bestfriend?

• Earthworms…– Break up/aerate soil

• Helps roots be able to penetrate soil• Helps water flow in soil

– Worm feces contain bacteria that help return N to soil

Parasitic Annelids????

Yep…you guessed it…

LEECHES!

Fun with Leeches!• Leech Facts:• There are 650 known species of leeches. • The largest leech discovered measured 18 inches. • The leech has 32 brains - 31 more than a human. • Not all leeches are bloodsuckers. Many are predators which eat earthworms, etc. • The bite of a leech is painless, due to its own anaesthetic. • The Hirudo leech injects an anti-coagulant serum into the victim to prevent the blood

clotting. • The leech will gorge itself until it has had its fill and then just fall off. • The leech will gorge itself up to five times its body weight. • The first leech was used in medicine about 1000 B.C., probably in ancient India. • In the past, people would stand in the lakes and pools dotted around the country and

when the leeches attached to their legs they would put them in baskets and sell them. Today the Hirudo leech is an endangered species.

• The nervous system of the leech is very similar to the human nervous system and is of enormous benefit to researchers in their quest for the answers to human problems.

• The nearest relatives of leeches are earthworms. • Leeches can bite through a hippo's hide!