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 #3. The Class: Monogenea

  1. hermaphrodites
  2. normally ectoparasites on aquatic vertebrates
  3. generally site specific on host and host specific
  4. live a few days - years, depending on species
  5. morphology
    1. Prohaptor [may be present, anterior end that may bear adhesive or feeding organs]
    2. Eyespots [may be present, photoreceptors] near two anterior ganglia
    3. Tegument [living external layer]
    4. Alimentary tract
      1. mouth anterior, usually with prohaptor
      2. esophagus with muscular pharynx
      3. intestine branches into cecae, often with diverticula
      4. Monopisthocotylea feed mainly on epidermis and mucus; Polyopisthocotylea mainly on blood, host cells, and mucus
      5. blind-ended gut, regurgitate waste
    5. Protonephridia [excretion]
      1. 2 main lateral ducts, extend posteriorly; then curve and extend anteriorly
      2. contractile bladders laterally
      3. flame cells drive fluid within ducts
    6. Reproductive systems
      1. Male
        1. 1-200 testes (1-2 most common)
        2. testes - vas efferens - vas deferens - seminal vesicle - cirrus - gonopore; sometimes prostate
      2. Female
        1. 1 ovary, normally anterior to testes
        2. oviduct from ovary - ootype
        3. Mehlis gland lubricates uterus, forms egg shell capsule
        4. genitointestinal canal, only in Polyopisthocotylea; connects oviduct with right intestinal caecum for excess secretions discharge
        5. 0-2 vaginas - sperm transfer; if none, use gonopore
        6. sometimes a seminal receptacle
        7. vitellarial secretions add to egg-shell formation; ducts fuse near oviduct
        8. eggs pass through uterus, out gonopore; sometime a muscular metraterm
    7. Development
      1. eggs shed, normally with filaments
      2. filaments stick to host
      3. oncomiracidium
        1. ciliated
        2. hooked posteriorly
        3. about a 24 hr life
        4. if eyespots, phototactic
        5. some attracted to fish mucus
        6. grow to adult directly
    8. Opisthaptor
      1. suckers (=suckerlets)
      2. anchors (large hooks, sometimes called hamuli or central hooks)
      3. hooklets (left over larval hooks, sometimes called marginal hooks)
      4. bars (often called accessory sclerites; they support anchors)
      5. clamps (complex, muscular structures more advanced than suckers)

Two Subclasses of Monogenes

  1. SUBCLASS: Monopisthocotylea (Polyonchoinea)
    1. opisthaptor single unit
    2. oral sucker absent
    3. eyes common
    4. genitointestinal canal usually absent
  2. SUBCLASS: Polyopisthocotylea (Polystomatoinea and Oligonchoinea)
    1. opisthaptor complex
    2. oral sucker or other oral structures
    3. eyes usually absent
    4. genitointestinal canal usually present

SUBCLASS: Monopisthocotylea

  1. main taxonomic features:
    1. size and arrangement of anchors, bars, and hooklets
    2. number and arrangement of testes
  2. Some representative species:
    1. Gyrodactylus spp. (Gyrodactylidae)
      1. live-bearers (embryos inside)
      2. no eyespots
      3. 16 hooks
      4. 1 pr anchors
      5. horns anteriorly
      6. common pests on trout, blue gill, catfish, and goldfish
      7. no oncomiricidium, so fish/fish contact
    2. Dactylogyrus spp. (Dactylogyridae)
      1. 1 pr anchors
      2. 14 hooklets of equal size and 1 accessory pair that are smaller [if 16 hooks of equal size, then Pellucidhaptor]
      3. 2 eyespots
      4. common on cyprinids, goldfish, carp
    3. Cleidodiscus spp. (Dactylogyridae)
      1. 2 pr anchors
      2. 2 bars
      3. 4 eyespots
      4. 14 hooklets
      5. Cleidodiscus pricei important, on catfish gills

SUBCLASS: Polyopisthocotylea

  1. main taxonomic features
    1. number and arrangement of suckers (=suckerlets or clamps)
    2. shape of disc-like trunk (=cotylophore)
  2. mainly gill parasites of fish; many in urinary bladder of herps
  3. most suck blood
  4. representative species:
    1. Polystoma integerrimum
      1. urinary bladder of old world frogs
      2. worms dormant until frog hormones in Spring trigger activity
      3. worms copulate in spring - eggs to exterior with urine - hatch 3-5 wks - oncomiricidium attaches to tadpole gill - develop into neotenic adults which are morphologically different than bladder adults (i.e. 2 rather than 6 suckers on opisthaptor) - produce eggs - hatch in 2-3 wks - oncomiricidium attaches to gills of new tadpoles - as gills lost and internal ones developing when frog undergoing metamorphosis, monogene migrates down gut to bladder - may take up to 5 yr for bladder forms to mature
      4. Similar genera and species in North American amphibia and reptiles:
        1. Neodiplorchis scaphiopodis in urinary bladder of spadefoot toads, Scaphiopus bombifrons
        2. Neopolystoma spp. in urinary bladder, nostrils, or conjunctival sac of turtles
        3. Polystoma nearcticum in urinary bladder of Hyla spp.
        4. Polystomidella spp. in urinary bladder of turtles
        5. Polystomoides spp. in oral cavity or urinary bladder of turtles
        6. Pseudodiplorchis americanum in urinary bladder of Scaphiopus couchii
        7. The genus Sphyranura on caudata probably represent neotenic stages of anuran polystomes
    2. Discoctyle spp. [in salmonids]
    3. Oculotrema hippopotami [eyes of the Hippopotamus]

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