Vocabulary List

1. Vocabulary List • Crop • Gizzard • Nephridia • Setae • Clitellum • Metamerism • Parapodia • Tagmatization

2. Chapter 13 Phylum Annelida

3. Characteristics of Phylum Annelida • Body is metameric (segmented arrangement of body parts) • Bilateral symmetry and wormlike • Closed circulatory system • Includes over 10,000 species of segmented worms-most are marine • Triploblastic Coelomates

4. Characteristics of Phylum Annelida • Live everywhere except in frozen soil of polar regions and in the sand of dry deserts • Include earthworms, marine worms, and parasitic leeches • Different from flatworms and roundworms because they are segmented and have a coelom

5. Taxonomy of Annelida: • Kingdom Animalia • Phylum Annelida • Class Polychaeta • Class Clitellata

6. Class Clitellata • Characteristics: • Clitellum in cocoon formation • Monoecious • Few or no setae • Two subclasses: • Oligochaeta (earthworms) • Hirudinea (leeches)

7. Subclass Oligochaeta • Over 3,000 species • Habitat: • Freshwater • Few estuarine • Some marine • Terrestrial • live in soil • during hot weather, may burrow 3 meters down

8. Lumbricusterrestris • Earthworm • No parapodia • Cuticle covers body • Body segmented with short setae • Clitellum: • Swollen set of segments in the anterior half • Will secrete mucus during copulation • Forms a cocoon

10. Subclass Hirudinea • Leeches • About 500 species • Most are freshwater • Predators of small invertebrates • Feed on body fluids of vertebrates (parasites)

11. Class Polychaeta • Largest class (more than 5,300 species) • Mostly marine • Habitat: • ocean floor • Under rocks, shells • Crevices of coral reefs • Burrow through substrate (tubeworms)

12. Segments with extensions called parapodia • Numerous setae (bristles) • First body segment called the peristomium: • has mouth, protomium, sensory tentacles (cirri) & 2 to 4 pairs of eyes • May be predators, herbivore, scavengers, or filter-feeders

14. Metamerism & Tagmatization • Segmental arrangement of body parts in an animal. • It influences every aspect of annelid structure & function • The compartmentalization of the body has resulted in each segment having its own excretory, nervous, and circulatory structures. • The specialization of body regions in a metameric animal. • Although it is best developed in the arthropods, some annelids also display tagmatization. • Greek “tagma” means arrangement

15. Advantages of Metamerism (segmentation) • Creation of hydrostatic compartments • Lessens the impact of injury • Permits the modification of certain regions of the body for specialized functions, such as feeding, locomotion, and reproduction.

16. Feeding & Digestion • Running through all earthworm segments from the mouth to the anus is the digestive tract (a tube in a tube) • Food and soil taken in by the mouth pass through the pharynx into the crop, where they are stored until they pass to the gizzard (gizzard is a muscular sac containing hard particles that help grind soil and food before they pass into the intestine).

17. Feeding & Digestion • Nutrients are absorbed from the intestine • Undigested material passes out of the worm’s body through the anus • Parasitic annelids have pouches along the digestive tract that hold enough food to last for months!

18. Circulation • Closed circulatory system. Oxygen and nutrients move to various parts of their bodies through their blood vessels. • At the same time carbon dioxide and metabolic wastes are removed from the blood and excreted. • Some of the vessels at the anterior end, or head, are large and muscular and serve as hearts that pump the blood. • The blood moves toward the anterior end of the worm in the dorsal blood vessel and toward the posterior end in the ventral blood vessel. • An earthworm has five hearts that pump blood through its circulatory system!

19. Respiration & Excretion • Segmented worms have 2 nephridia in almost every segment. • Cellular waste products are collected in the nephridia and are transported in tubes through the coelom and out of the body. • Nephridia also function in maintaining homeostasis of body fluids of annelids, ensuring that the volume and composition of body fluids are kept constant.

20. Response to Stimuli • Anterior segments are modified for sensing the environment • You might have seen an earthworm quickly withdraw into its burrow when you shine a flashlight on it or step close to it….these observations show that earthworms can detect both light and vibrations.

21. Movement • When an earthworm moves, it contracts circular muscles running around each segment. • This squeezes the segment and causes the fluid in the coelom to press outward like paste in a tube of toothpaste being squeezed. • Because the fluid in the coelom is confined by the tissues between segments, the fluid pressure causes the segment to get longer and thinner… • Next, the earthworm contracts the longitudinal muscles that run the length of its body. • This causes the segment to shorten and return to its original shape, pulling its posterior end forward and resulting in movement!

22. Movement • Many annelids have setae on each segment. Setae are tiny bristles that push into the soil and anchor the worm during movement. • By anchoring some segments and retracting others, earthworms can move their bodies forward and backward segment by segment!

23. Reproduction • Annelids can reproduce both sexually and asexually. • Most annelids have separate sexes, but some, such as earthworms and leeches, are hermaphrodites. • Sperm are passed between two worms near segments called clitellum (a thickened band of segments). • It produces a cocoon from which young earthworms hatch. • Sperm and egg pass into the cocoon as it slips forward off the body of the worm. • After fertilization, the young are protected in the cocoon as they develop. • Some annelids reproduce asexually by fragmentation. • If a worm breaks apart, the missing parts can be regenerated.

24. Earthworm reproduction • Monoecious & Exchange sperm • Copulation: Two worms line up in opposite directions • Clitellum of one lines up with genital segments of other • Mucus holds worms together • Sperm travel from one to the other • Last 2-3 hours • After copulation, a cocoon is formed around worm • Mucus, food, eggs and sperm are deposited in the cocoon • Fertilization occurs in the cocoon • Worms back out of the cocoon and it drops to the ground • Hatching – takes a few weeks

26. Earthworms • Probably the best known annelids • Used as bait for fishing and are found in garden soil. • Can eat its own mass in soil every day! • Earthworms ingest soil to extract nutrients…in this way, earthworms aerate the soil-they break it up to allow air and water to move through it (my mom always said, you know you’ve got good dirt if you find a worm)

27. Marine Annelids • Include bristleworms and fan worms • Have head regions with well-developed sense organs, including eyes. • Most body segments also have a pair of appendages called parapodia that are used for swimming and crawling • Fan worms are sessile and filter feeders, they trap food in the mucus on their fan-shaped structures. • If there is a threat nearby, fan worms retreat into their tubes.

28. Leeches • External parasites • Flattened bodies and usually no setae • Most live in freshwater streams or rivers where they attach to the bodies of their hosts-including fishes, turtles, and humans. • Leeches attach to their hosts using front and rear suckers. • When a leech bites, it saliva contains chemicals that act as an anesthetic. • Other chemicals in the saliva reduce swelling and prevent the host’s blood from clotting. • They maintain blood flow after microsurgery.

30. Medicinal leeches • http://video.nationalgeographic.com/video/player/places/countries-places/india/india_leechescure.html

31. http://www.leeches.biz/medicine-leech.htm