Whacky parasite life cycles - your nominations please!

Ian Barger ibarger at chiswick.anprod.CSIRO.AU
Wed Jul 6 20:47:57 EST 1994


On 1 Jul 1994 08:24:09 +0100, 
David Johnston  <daj at nhm.ac.uk> wrote:

>                                                       I am, therefore 
>looking for nominations for your favourite wierd, wonderful and whacky 
>adaptations and life cycles to illustrate my talk with; phenomenal 
>reproductive output, alteration of host behaviour, parasites of parasites. 
>You name it, I would be grateful to hear about it (with follow-up 
>references if possible).

How about the following direct quotation from a chapter by J F Michel and C 
B Ollerenshaw entitled Helminth Diseases of Grazing Animals in "Animal 
Health, Production and Pasture", edited by A N Worden, K C Sellers & D E 
Tribe, Longmans, London, 1963.

"Most parasites are extremely prolific.  A careful calculation concerning 
the reproductive capacity of Haemonchus contortus has been made and its 
results are illuminating.  If it be postulated that one male Haemonchus and 
one female Haemonchus on one thousand acres of pasture find conditions 
sufficiently favourable that they may reproduce at their normal rate, if 
none of their progeny dies prematurely and the life cycle is completed in 
five weeks, the adult worm living for a month, then at the end of seven 
months the rate of increase of the worms would be such that a layer of 
worms on the thousand acres would be increasing in thickness at such a rate 
that the top of it would be moving upward at a speed equal to the velocity 
of light.  It may be concluded that the reproductive potential of H 
contortus is not reached under normal conditions of husbandry."

Explanatory notes:  H. contortus is a common nematode parasite of sheep, J 
F Michel & C B Ollerenshaw are both highly regarded parasitologists and I 
would have every faith in the accuracy of their calculations.  Michel, 
in particular, is noted for his whimsical sense of humour.
_____________________________________________________________________________
Ian Barger,                   |The secret of success is sincerity. Once you |
CSIRO Animal Health           |can fake that, you've got it made.           |
Armidale NSW 2350, Australia  |_________________________Jean Giraudoux______|
ibarger at chiswick.anprod.csiro.au   



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