Earthworms and Leeches Phylum Annelida Earthworms and Leeches

About 9,000 species!

Segmentation Segmentation is also called metamerism. Segments each contain elements of such body systems as circulatory, nervous, and excretory tracts.

Setae…                        All annelids except leeches also have chitonous hair-like structures, called setae, projecting from their cuticle.

Metamerism Metamerism increases the efficiency of body movement by allowing the effect of muscle contraction to be extremely localized.

More Characteristics Internal organs are well developed Digestive system is a complete tube with mouth and anus Gases are exchanged through the skin Some have fairly well developed eyes Found throughout the world, in marine, freshwater, and terrestrial environments

Earthworms… Oligochaetes feed primarily on detritus and algae. Earthworms cycle huge quantities of soil through their guts, a process that speeds the turnover of nutrients in soil and increases productivity. They also help to aerate soil.

Leeches Class Hirudinea Most are free-living and eat small invertebrates, feeding on their blood Most live in freshwater environments, although a few can live in terrestrial environments

LEECHES! Small sucker in the anterior end and a larger one in the posterior end

Hirudin Leeches secrete chemicals that prevent the formation of blood clots into the host's blood One of these chemicals, hirudin, is the most powerful anticoagulant (substance that prevents blood clots) known.