Sara Ramirez & Albany Gonzalez

Annelids are small worms with segmented bodies that have a true coelom that is lined with tissue derived from mesoderm. Of the three major phyla of protostomes The name annelida derives from annellus which means “little ring” in Latin. The body of annelids is divided into segments that are separated by septa. In many annelids, bristles called setae are attached to each segment.

-Feeding and Digestion:  Many annelids get their food using a pharynx.  Carnivorous species’ pharynx usually holds two or more jaws to attack prey.  The ones that feed on decaying vegetation has pharynx that is covered with sticky mucus.  Other annelids obtain nutrients by filter feeding.  In earthworms, the pharynx pumps food and soil into the esophagus. -Circulation:  Annelids typically have closed circulatory systems, in which blood is contained within a network of blood vessels.  An earthworm’s blood circulates through two major blood vessels that run from head to tail.  These two veins are the dorsal and ventral vessels.  The dorsal blood vessel functions like a heart because it contracts rhythmically and helps pump blood.

-Respiration  Aquatic annelids often breathe through gills.  Land-dwelling annelids, such as earthworms, take in oxygen and give off carbon dioxide through their moist skin. -Excretion:  Annelids produce two kinds of waste:  Disgestive waste passes out through the anus at the end of the digestive track.  Cellular waste containing oxygen is eliminated by nephridia, which are excretory organs that filter fluid in the coelom. -Response:  Most annelids have well- developed nervous systems consisting of a brain and several nerve cords.  Most of these sense organs are best developed in free living marine annelids.  Many of these species have a variety of adaptations for detecting stimuli: sensory tentacles, chemical receptors, statocysts that help detect gravity, and two or more pairs of eyes.

-Movement:  Annelids have two major groups of body muscles that function as part of a hydrostatic skeleton:  Longitudinal muscles run from the front of the worm to the rear.  Circular muscles rap around each body segment.  The earthworm moves by alternately contracting these two sets of muscles using it’s setae to prevent slipping. -Reprodution:  Most annelids reproduce sexually.  Some annelids are hermaphrodites.  Individuals rarely fertilize their own eggs.  When the eggs are ready for fertilization, a clitellum secretes a mucus ring into which eggs and sperms are released. Fertilizition takes place within this ring.  Then the ring slips off the worm’s body and forms a protective cocoon.  Young worms hatch weeks later.

Polychaetes are marine annelids that have paired, paddle-like appendages tipped with setae. The class of Polychaetes contain sandworms, bloodworms, and their relatives. Polychaetes live in cracks and crevices in coral reefs, in sand, mud, and piles of rocks, and sometimes out in the open water. Polychaetes

Oligochaetes are annelids that typically have streamlined bodies and relatively few setae compared to polychaetes. Most oligochaetes live in soil or fresh water. Earthworms and Tubifex worms are examples of Oligochaetes. Oligochaetes

LEECHES: Part of the class, Hirudinea Leeches mostly live in moist habitats in tropical countries and can be found in shallow ponds, lakes, and marshes. Leeches are external parasites that suck on the blood and body fluids of their host. 1/4 th of all leeches are carnivores that feed on soft-bodied invertebrates. Some leeches force a muscular extension called a proboscis into the tissue of their host. Others slice into the skin with razor-sharp pair of jaws. Leeches were once used to treat medical conditions. Hungry Leeches are used after surgery since they can reduce swelling. Leeches can suck several milliliters of blood at a time, five times their own weight.