Segmented Worms Earthworm Phylum Annelida Segmented Worms Earthworm

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. The earthworm has two sets of muscles; one that makes it long and thin and one that makes it shorter and fatter. Rear Anchor→ Elongation → Front Anchor→ Pull

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, An esophagus 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 Earthworm Systems

Nervous System A earthworm has a nervous system with a simple brain (cerebral ganglion)and ventral nerve cord.

Circulation A earthworm has blood and blood vessels with multiple (5) hearts.

Annelids have a “Closed” Circulatory System The blood stays in vessels and basically travels in a loop… Hearts pump blood into the Dorsal blood vessel (to body) and back to heart in the ventral blood vessel

Respiration A earthworm has no respiratory organs. 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. This is called ______________ hermaphrodites However, the eggs must be fertilized by the sperm of another worm.

Reproduction (cont.) Yes, Earthworms are hermaphrodites, but they still must cross-fertilize to produce offspring 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 and sperm from special reproductive pores and then slips off the worm's head. The embryos develop within the cocoon. Earthworm - Lumbricus terrestris - ARKive - video 09

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.

Did you know that Earthworms are a gardeners bestfriend? 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!