Biology 625
Fall semester lecture note outline

Updated: 24 September 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 #14: Superorder: Eucestoda; Infracohort: Pseudophylla

  1. one embryonic membrane (no embryophore)
  2. oncospheres with unicellular protonephridium
  3. polylecithal eggs (a large component of vitelline material forming a true shell that is quinone tanned)
  4. oncospheres of the order: Pseudophyllidea often ciliated
  5. three orders in this group

Order: Caryophyllidea

  1. scolex unspecialized or with shallow bothria
  2. monozoic
  3. genital pores midventral
  4. testes numerous; ovary posterior; single sets of each
  5. vitellaria follicular
  6. uterus a coiled medium tube
  7. thought to be evolved from pleurocercoid neoteny (i.e., adults technically neotenic pleurocercoids)
  8. in teleost fish, or aquatic annelids
  9. life-cycle (i.e. 1969, Proc Helminthol Soc Wash 36: 119-126)
    1. adults in gut
    2. eggs released
    3. mature in water; hatch
    4. eaten by aquatic annelid
    5. procercoid forms
    6. eaten by fish
    7. matures directly in gut
  10. 1972, Exp Parasitol 31: 417-512
    1. theory is that segmented adults at one time in aquatic reptiles
    2. adults became extinct and only survivors were pleurocercoids that had the ability to directly mature within the second intermediate host (fish)
    3. a few species are even capable of developing into mature adults in annelids (i.e. neotenic procercoid); cercomer retained

Order: Spathebothriidea(do not learn for test)

  1. scolex feebly developed, either undifferentiated or with funnel-like apical organ or 1-2 hollow cuplike organs
  2. constrictions between proglottids absent; proglottids only distinguished by internal segmentation details
  3. testes in two lateral bands; ovary dendritic; more than one set of reproductive structures
  4. vitellaria follicular, either lateral or scattered
  5. uterus coiled
  6. in teleost fish
  7. 1969, J. Fish Res Board Canada 26: 975-996

Order: Pseudophyllidea

  1. Scolex with two bothria; some with hooks
  2. Testes numerous
  3. Ovary posterior
  4. Vitellaria follicular, either lateral or cortical
  5. Eggs usually operculate; often with coracidium (ciliated)
  6. Uterine pore present, either dorsal or ventral
  7. In all vertebrate groups. Some representative species below:

Diphyllobothrium latum (broad fish tapeworm)

  1. Common in fish eating carnivores, especially in Northern Europe; also in the great lakes region and West Coast.
  2. Similar species, including D. ursi in North America and D. chordatum and D. pacificum in pinnipeds in the Pacific basin
  3. Adult worms up to 10 meters in length; proglottids wider than long
  4. Life-cycle
    1. adults in gut
    2. strings of proglottids break off strobila
    3. Eggs into environment; matures; hatches
    4. Coracidium
    5. Eaten by crustacean
    6. Procercoid forms
    7. Eaten by fish
    8. Pleurocercoid in muscles
    9. Two possibilities
      1. Eaten by paratenic host (i.e. larger fish; reptiles; mammals; etc.) (Pleurocercoid crosses gut and enters muscle of new fish); eventually paratenic host ingested by definitive host and adults develop in gut
      2. Eaten by definitive host, where adults develop in gut
  5. Other genera
    1. Ligula spp. in birds
    2. Diplogonoporous spp. in whales

Diphyllobothrium (Spirometra) mansonoides

  1. Occurs in the intestine of felids, some canids, in North America
  2. Similar species, Diphyllobothrium (Spirometra) erinacei in carnivores in orient.
  3. Life-cycle
    1. Adults in cats
    2. Eggs out with feces; into water; hatch
    3. Coracidium eaten by copepod
    4. Procercoid
    5. Eaten by amphibian, reptile, or mammal
    6. Pleurocercoids in muscle (sparganosis); also in viscera in the mammals
      1. Eaten by cat; adults in gut
      2. Eaten by other mammals; pleurocercoids traverse gut and become dormant again in muscles or viscera
  4. Pleurocercoid growth factor released by pleurocercoids of D. mansonoides and D. erinacei.
    1. accelerates growth in some animals; i.e. rats
    2. cysteine proteinase activity; probably helps pleurocercoid migrate through tissues
    3. also a human growth hormone analog
    4. can cause increased weight gain due, in part, to fat deposition; increased skeletal growth

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