Biology 625
Fall semester lecture note outline

Updated: 21 October 1999

The text below simply represents a crude lecture outline of one of the topics covered in class. It is not meant to substitute for attending lectures or ignoring the textbook. Additional material, including line drawings, kodachromes, and more extensive information on life-cycles and basic biology, will be supplied in the lectures.

TOPIC 50. Hirudinea (leeches)

  1. one of the 3 classes of the phylum: Annelida
  2. most species live in freshwater environments; some terrestrial
  3. many predatory or scavengers; perhaps 25% parasitic
  4. most with 34 true internal segments; outer surface annulated
  5. with anterior (pseudosucker) and large posterior suckers
  6. most without setae
  7. some can swim; others cannot
  8. complete gut; sometimes with diverticulae
  9. some species with eyes
  10. sensory papillae embedded over body surface
  11. male reproductive system
    1. 4-80 pair of testes
    2. spermatozoa cemented together in seminal vesicles and enter ejaculatory ducts (2); these fuse to form an atrium
    3. most species pass sperm as spermatophores; the Hirudidae possess a penis instead
  12. female reproductive system
    1. 2 ovaries
    2. oviducts unite to form uterus
  13. typical life-cycle
    1. species are hermaphroditic
    2. in most, spermatophores are released onto the body surface of the partner and enter tegument via histolytic enzymes; migrate through coelom to fertilize oocytes within the ovaries
    3. in the Hirudidae, the penis places sperm within the female gonopore
    4. the clitellum is inconspicuous and secretes rings which collect fertilized ova as they pass anteriorly over the female gonopore and are sloughed off the anterior end of the body as cocoons (May-August)
    5. young leeches hatch and exit cocoon; similar to adults
    6. development usually takes some years to complete
  14. 4 orders:
    1. order: Acanthobdellida
      1. primitive, with 1 species (Acanthobdella) on salmonids in Europe
      2. setae present
      3. coelom as compartments in 5 anterior segments
    2. order: Gnathobdellida
      1. large mouth
      2. non-eversible pharynx
      3. 3 pair jaws
      4. testes large and arranged in metameric pairs
      5. aquatic or terrestrial
      6. 5 annuli per segment
      7. typical genera include Hirudo, Macrobdella, Limnatis
        1. Hirudo medicinalis is the European medicinal leech
        2. Hirundinaria granulosa is the Indian medical leech
        3. Hirundinaria zeylandica is the terrestrial leech that attacks humans and animals in the tropics of Asia
        4. Limnatis nilotica is the large horse leech in Europe; members of the genus are sometimes accidently ingested by various animals and attach and suck blood along the esophagus and nasopharyngeal area. Often used for bloodletting in Europe
    3. order: Pharyngobdellida
      1. large mouth
      2. non-eversible pharynx
      3. without true jaws or dentition
      4. testes in grape-like bunches
      5. mostly aquatic; some semi-terrestrial
    4. order: Rhynchobdellida
      1. mouth small, as a pore
      2. eversible proboscis derived from pharynx
      3. without jaws or dentition
      4. all aquatic
      5. typical genera include Glossiphonia, Haementeria, Placobdella
        1. Haementeria officinalis the medicinal leech of Central and South America
        2. Placobdella parasitica the common turtle leech in Kansas

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