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another defini post

ctfaulkn at utkvx.utk.edu ctfaulkn at utkvx.utk.edu
Thu Mar 30 09:09:30 EST 1995

In Article <Pine.HPP.3.91.950329072554.7868C-100000 at ac852.wfunet.wfu.edu>
zelmeda4 at WFU.EDU ("derek a. zelmer") writes:
>On 1 Mar 1995, Jeffrey Lotz wrote:
>> Even on sematic (rather than empirical) grounds, I would argue 
>> against the restriction of parasite to pathogen. If we restrict 
>I think that removing host damage from the definition of a parasite only 
>creates more confusion. Mutualism and commensalism involve completely 
>different life history strategies that follow differnt pathways of 
	In an earlier post I commented on the sometimes "fine-line"
between being a commensal and a "parasite (pathogen)".  I think Jeff's
comments go a long way toward resolving the problems inherent in equating
parasite with pathogen.  Consider the pinworms as an example. As a general 
rule they cause no harm to tortises, and some have suggested that they play 
an important role in breaking down the hemicellulose in their diets, yet on
other occasions an excessive number of parasites coupled with inadequate 
nutrition results in serious disease, and even death.  What do you call these
parasites, facultative comensals (or pathogens).  
       Does endosymbiont necessarily imply that one organisim (the
endosymbiont) is metabolically dependent on the other (host), or does in just 
recognize that 2 organisms are traveling together ?   When I consider the 
Entamobea coli question (comensal or parasite), it seems appropriate to ask 
why is it not found in a wide range of vertebrate hosts, especially if all 
this species requires is predigested food?  Surely it must have other
requirments (gut pH, host hormones, etc.) that favor one host over others.
This seems to imply a metabolic dependency of sorts, or a parasitic state
of existance.  Perhaps someone pursuing these research questions can 
shed some light from an informed perspective. 

Another question, how long must a parasite (pathogen) be associated 
with a host before it becomes a comensal, and what sort of selective 
preassures favor this transition?

*      Charles T. Faulkner       *   When you don't know where you're
*  Univ of Tennessee, Knoxville  *   going any road will take you there.
*   (ctfaulkn at utkvx.utk.edu)     *                            Alice

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