ZOO 115 Invertebrate Zoology

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ZOO 115 Invertebrate Zoology

• Platyhelminthes
• Parasites

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Parasitism - Adaptations

• Method of attachment
• SUCKERS - Trematoda and Monogea

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Parasitism - Adaptations

• Getting into host
• Penetration special glands to digest skin

• Getting into host
• Passive eaten by host
• Need outer resistant covering
• Living tegument
• Permeable to H20, amino acids, sugars
• Tolerate great changes in pH.

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Parasitism - Adaptations

• Osmotic Pressure
• Must be lower than surroundings why?

• Facultative anaerobic respiration
• 4X more efficient than in vertebrates
• Reduced structures
• Sensory (except chemo)
• Muscles
• Nervous system
• Digestive tract

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Parasitism - Adaptations

• Increased reproduction
• Produce many many eggs
• e.g. Fish tapeworm 2 million eggs/day and can
  live for 15 yrs (100 trillion eggs in lifetime)
• Polyembryony many young from one egg.
• Asexual stages amplify numbers
• e.g. Fasciola hepatica produces 500,000 eggs in a
  lifetime that produce 42 trillion offspring.

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Parasitism - Adaptations

• Host reactions to parasites
• Susceptibility varies with life cycle and health
  of host
• Single host parasite usually becomes more
  commensal
• Castration
• Multiple hosts parasite can kill the host
• Snails
• Ants
• Internal parasites develop ways of hiding from
  immune system

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Parasitism - Adaptations

• Host specificity varies
• Some are completely specific to their hosts
• Problems with non-specificity
• Swimmers itch
• Nematode and encephalitis

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Class - Trematoda

• Common Name - Flukes
• Common parasites of all major vertebrate taxa.
• gt11,000 species

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Class Trematoda - General Anatomy of Adult

• Suckers for feeding and attachment

• Non-cliated tegument
• Protection against enyzmes,
• Gas exchange
• Eliminate nitrogenous waste
• Absorb glucose and amino acids

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Class Trematoda - General Anatomy of Adult
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Class Trematoda Life Cycles

• Chinese Liver Fluke (Opisthorchis or Clonorchis)
• Infests 20 million E. Asians
• Adult 2.5 cm in length
• Live 8 yrs
• Produce 4000 eggs per day for 6 mo
• Symptoms Jaundice, gallstones, debilitation and
  liver cancer

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Class Trematoda - Life Cycle
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Class Trematoda Life Cycles

• Blood Fluke (Schistosoma sp)
• Dioecious Male 6-10 mm, Female much smaller
  (fits into groove in male)
• Develop cercaria directly from sporocyst (no
  redia)

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Class Trematoda - Reproduction

• Why is amplification important?
• What impact might the multiple host strategy of
  the parasite have on the hosts?

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Class Monogenea

• Ectoparasites only one host
• Mostly infest fishes

• Adults have suckers and hooks

• Larvae hooked free-swimming (oncomiradium)

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Class Monogenea life cycles

• Dactylogyrus sp.
• More eggs with increasing temperature
• Eggs released sit on bottom
• Hatch into swimming larvae
• On contact with fish metamorphose into adult form

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Class Monogenea life cycles

• Polystoma sp.
• Eggs stay in frog until frog gets in water
• Hatch into swimming larvae
• Larvae attach to gills of tadpoles
• Tadpoles metamorphose and larvae crawls over
  belly and goes into bladder

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Class Cestoda

• Common name Tapeworms
• 3400 species
• Gut is absent specialized neodermis for
  nutrient uptake.
• Live about 15-20 yrs
• Can copulate

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Class Cestoda - Anatomy

• Can reach 15 m in length!

• Head region
• Attach to preys intestinal tract

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Class Cestoda - Anatomy

• Proglottids
• Each is a complete hermaphroditic reproductive
  system
• Both Cross and Self-Fertilization

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Class Cestoda Life Cycles
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Class Cestoda Life Cycles

• If eggs go in water
• swimming larvae (onchosphere) hatches within 10
  days
• Eaten by copepods
• Copepods eaten by fish
• Penetrates gut, migrates to muscle and
  transformed into dormant miniaturized adult
• Eaten by warm-blooded host

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Class Cestoda Life Cycles

• If eggs go on land
• Eggs eaten by cattle
• Onchosphere larvae hatch, bore into intestinal
  wall and transported through circulatory system
  to muscle tissue
• Develops into bladderworm larvae (Cysticercus).
• Eaten by warm-blooded host.

http//sps.k12.ar.us/massengale/tapeworm.gif
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Class Cestoda

• Causes Diarrhea, Weight loss and inflammation
• Biggest problem is accidental infestations
• Bladder worm will develop into tissue other than
  muscle.
• Cyst can contain liters of fluid which could
  cause severe infection if released