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Phylum Annelida

Phylum Annelida. Annelida. Paleontologists believe in the pre-Cambrian era the only animals on Earth were sponges, cnidarians and ancestral bilateral worms.

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Phylum Annelida

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  1. Phylum Annelida

  2. Annelida • Paleontologists believe in the pre-Cambrian era the only animals on Earth were sponges, cnidarians and ancestral bilateral worms. • A group of animals called annelid worms developed during the Cambrian Explosion. Today, about 15,000 species of annelids exist including earthworms, marine bristle worms, and leeches. • Scientists believe that burrowing worms play a vital role in maintaining life on Earth by recycling plant and animal remains into carbon dioxide gas. This gas helps modify the climate of the biosphere. • Before active burrowers appeared, organic remains became buried in sediments and depleted the atmosphere of carbon dioxide. • With sufficient carbon dioxide in the air, land plants can thrive and the oceans remain free of ice across much of the planet.

  3. Phylum Annelida • Segmented body • metameric • Setae • Bristles or hairs • Absent in leeches • Coelom divided by septa • Closed circulatory system • Nephridia for each segment (metamere)

  4. Segmented Worms • Body divided into repeating segments

  5. Sedentary- don’t move

  6. Terrestrial • Earthworm

  7. Feed on Blood • Leech

  8. Uniramia Echinodermata Chelicerata Vertebrata Lophophores Crustacea Other Chordata Annelida Arthropoda Hemichordata Mollusca Other pseudocoelomates Nemertea Platyhelminthes Ctenophora Nematoda Cnidaria Mesozoa Placozoa Sarcomastigophora Ciliophora Porifera Apicomplexa Microspora Myxozoa

  9. Trochophore larva Apical tuft Stomach Ciliary band Mouth Anus

  10. Annelid development

  11. Phylum Annelida Body Plan • Cylindrical, bilateral, & segmented • True coelom • Complete digestive system • Closed circulatory system

  12. Phylum Annelida Body Plan • Annelids have a true body cavity or coelom that is located between layers of mesoderm • Annelids are the first major phyla showing segmentation (metamerism) which is advantageous to movement, safety, and tagmatization (specialization of body regions)

  13. Circulatory Systems Open Closed- Annelids Annelids have 5 hearts

  14. Feeding and Digestive System • Annelids have a complete digestive system • Their system contains mouth, pharynx, esophagus, crop, gizzard, intestine and anus • They use muscles to help in the mechanical digestion of food

  15. Digestive System

  16. Septa Metamerism Pygidium Prostomium Peristomium

  17. Movement • Each annelid segment contains its own longitudinal and circular muscles • These muscles work antagonistically, such that when the longitudinal muscles contract the circular muscles relax and the segment become short and thick • In contrast, when the circular muscles contract, the longitudinal muscles relax and the segment becomes long and thin

  18. Reproduction • Class Oligochaeta are hermaphroditic and during copulation they line up facing in the opposite direction • The clitellum secretes a mucous that holds the worms in place • Later, the clitellum acts as a cocoon where the fertilized egg develops Oligochaeta

  19. Classification • Class Polychaeta (many hairs) • Class Oligochaeta (few hairs) • Class Hirudinae (leeches)

  20. Class Polychaeta • Hairy worms • Many setae • Hairs or bristles made of chitin • Parapodia • Paired projections on each segment • Like feet or flippers • Used for locomotion • Mostly marine • 1mm – 3m in length

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