|Annelid Puzzle Solution|
The phylum Annelida contains feather duster worms, common earthworm, and leeches. Annelids have both internal and external segmentation. This makes the annelid’s body look like a series of rings. Annelids have bilateral symmetry and a true coelom or body cavity. Their coelom is filled with fluid which their muscles push against. Many annelids have external bristles or setae and some have flashy protrusions called parapodia that appear paddle like. There three classes of annelids including Oligochaeta, Polychaeta, and Hirudenia. All classes have well developed organ systems.
Earthworms live in the soil, move by setae, and are in the class Oligochaeta. Earthworms have many longitudinal and circular muscles to aid in movement. The clitellum is a swollen band on the earthworm involved in reproduction. The digestive tract of an earthworm includes the mouth, pharynx, esophagus, crop, gizzard, intestine, and anus. The pharynx helps suck food into the mouth while the crop temporarily stores food and the gizzard grinds the food. Absorption of food takes place in the intestine. Wastes leave the earthworm’s body through the anus. Five pairs of hearts or aortic arches pump blood through the earthworm’s body. Nephridia are tubules that filter & get rid of wastes from the earthworm’s blood. Chitin, a tough carbohydrate, surrounds and protects the earthworm. Earthworms reproduce sexually by exchanging sperm; however, they are hermaphrodites. Exchanged sperm is stored in seminal receptacles until fertilization. Fertilized eggs are placed in a cocoon made by the clitellum until they hatch.
Hirudenia contains leeches. Many leeches are external parasites that feed on blood. Leeches lack setae or parapodia. Leeches secete a chemical into the body of their hosts so the blood does not clot. Some leeches feed on small invertebrates. Leeches have suckers for movement and attachment at both ends of their bodies. Most leeches live in freshwater.
Polychaetes move by parapodia and may also use them for respiration or gas exchange. Polychaetes have sensory antenna with strong jaws. Polychaetes live in marine environments.