ZOO 115 Invertebrate Zoology Phylum Annelida Class Clitellata

ZOO 115 Invertebrate Zoology Phylum Annelida Class Clitellata Subclass Oligochaeta

Subclass Oligochaeta - General Characteristics n > 3500 species n n Most terrestrial or freshwater but about 200 marine species Includes earthworms n 3 m Australian earthworm http: //www. ahc. gov. au/publications/pnh/images/ea 10597. jpg

Subclass Oligochaeta - General Characteristics n They have few chaetae n n Usually simple with typically four bundles per segment. retractable Retractor muscle Protractor muscle http: //www. infovisual. info/02/img_en/007%20 Internal%20 anatomy%20 earthworm%20 cross. jpg

Subclass Oligochaeta - external anatomy http: //www. howe. k 12. ok. us/~jimaskew/botzo /wormx. gif

Subclass Oligochaeta locomotion n Like Polychaetes - have septae separating segments into compartments making peristalsis more efficient. Musculature similar to Polychaetes During dry seasons and winters, earthworms burrow deeper (up to 3 m) n Become dormant (diapause) and dehydrated

Subclass Oligochaeta - Nervous system Brain Mechanoreceptors on each segment - more concentrated in prostomium Chemosensory tubercles - form three rings on each segment - more concentrated in prostomium Photoreceptors on each segment - more concentrated in prostomium Ventral Nerve Cord

Subclass Oligochaeta - Nervous system Brain Segmental nerves - attach to longitudinal muscles How do you think this animal responds to a sudden stimulus? Contains 5 giant axons Ventral Nerve Cord

Subclass Oligochaeta - Feeding and Digestion n n Scavengers Muscular pharynx Deposit n Suction feeders n n Adhesion in some aquatic sp. Pharyngeal glands digestion http: //www. miramar. sdccd. net/programs/biol/earthworm/

Subclass Oligochaeta - Feeding and Digestion n Crop Gizzard Intestine n n Chiton Only in lined Earthworms Muscular Used for Grinding storage Typhosole http: //www. emc. maricopa. edu/faculty/farabee/BIOBK/Bio. Book. Diversity_8. html - fold in intestine to increase surface area http: //www. emc. maricopa. edu/faculty/farabee/BIOBK/Bio. Book. Diversity_8. html http: //www. miramar. sdccd. net/programs/biol/earthworm/

Subclass Oligochaeta - Circulatory system n Similar to other Annelids n Many have multiple hearts Contractile Dorsal blood vessel http: //www. backyardnature. net/pix/earthwm 1. gif Blood Flow

Subclass Oligochaeta - Excretion n Metanephridia n Usually one pair per segment emc. maricopa. edu/faculty/farabee/BIOBK/Bio. Book. Diversity_8. html

Subclass Oligochaeta - Respiration n Mostly by diffusion through the body wall A few species have gills Aquatic tolerate low oxygen

Subclass Oligochaeta - Respiration n Calciferous glands n n n Secrete Calcium Carbonate Function not entirely known. Thought to play a role in CO 2 removal http: //www. backyardnature. net/pix/earthwm 1. gif

Subclass Oligochaeta Reproduction nn Sexual Asexual n n - common in aquatic species Hermaphrodites Copulation Breed continuously n Genital Chaetae hold the worms together n In common earthworms, the gonopores don’t line up and the sperm have to swim n Male reproductive organs Female reproductive organs Clitellum http: //images. encarta. msn. com/xrefmedia/aencmed/ targets/illus/ilt/T 013733 A. gif

Subclass Oligochaeta Reproduction n Clitellum n n Often most pronounced during mating period Creates mucus for copulation n Works in conjunction with special muscles to create slippery furrows for swimming sperm in earthworms Creates a cocoon for the eggs Clitellum Direct Development n 12 weeks to hatch Can live several years http: //images. encarta. msn. com/xrefmedia/aencmed/targets/illus/ilt/T 013733 A. gif n

Earthworms importance to Agriculture n Burrowing n n n aerates the soil to provide air and water for plants Reduces runoff and surface evaporation of water Encourage growth of other organisms that have a detrimental effect on Nematodes

Earthworms importance to Agriculture n Digestion of organic material n Per acre per year on cultivated land, 16, 000 pounds (7200 kg) of soil pass through earthworm guts and are deposited atop the soil -- 30, 000 pounds n Fecal material (castings) n Rich in nutrients. n n High in Nitrogen, Magnesium, Phosphorus, Calcium, Potash Neutralizes p. H.