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DEFINITIONS & energetics

Brian E. Keas keasbe9 at WFU.EDU
Sat Mar 25 12:53:53 EST 1995

I'm not quite sure what's going on or if it happened to others, but as I 
logged on today my e-mail messages included a post from me and Tim Ruhnke
dated back in February.   

Tim states:
> sure, one can engage in semantic 
> discussions (arguments?) about THE definition of parasitism, as if there 
> might be one.  no, a ship's hull is not a host, neither is a petri dish.  
> .....  others then argue points about definitions, 
> as if that might vitiate the idea raised.  of course, most of the 
> interesting arguments i've heard (and participated in!!) along this line 
> have been in bar rooms, not class rooms.  so i guess we know there proper 
> province.
According to the responses I've read, the discussion of the definition 
of a parasite is quite valid.  From various responses, I have had the 
opportunity to get a feel for the wide range of ideas about parasites 
that exist in the community of parasitologists.  

In addition, discussion about such issues (call it SCHOLASTICISM if you 
want) is not an end in itself but leads to further discussion of ideas 
raised by the initial question.  To me, this is the chief benefit of this 
newsgroup.  Not that I can get an answer to a question that could be 
found easily in a textbook, but that discussions can be facilitated 
between many different types of people specializing in various fields 
within (or even outside of) parasitology.

For example, in a previous post regarding the definition of a parasite, 
the issue of predators gaining benefits by eating parasitized 
intermediate hosts was raised as a possible "problem" in the definition 
of a parasite as being harmful to its host.  I thought that this was an 
intriguing example but I personally knew of little work 
done on the energetics between hosts and parasites, specifically with 
regards to predator/prey interactions and asked for some references.

The ONE response I received came from Vince Connors directing me to some 
work that had been done with starlings and acanthocepahalans:  Connors, V.A. 
and B.B. Nickol.  1991.  Effects of _Plagiorhynchus cylindraceus_ 
(Acanthocephala) on the energy metabolism of adult starlings, _Sturnus 
vulgaris_.  Parasitology 103:395-402.
This work shows a parasite's effect on a host, which had been studied 
previously and in which no pathogenicity was reported (Moore and Bell,
1983 J. Parasitology 69:387-390), to indeed be detrimental to the host 
when different variables were studied.  In this case, the parasite 
altered host basal metabolism and thermal regulation.  These effects were 
especially detrimental when the birds were temperature stressed (kept at 
4 C).  
This work underscores the idea that while one aspect of a parasite's 
interaction with a host may seem inconsequential or even benefit the 
host, it is important to examine the "big picture" to determine the 
overall effect of a parasite on its host. Individual studies cannot do 
this alone.  But because one study is published saying one thing, does 
not mean that it is the final word on the subject and that further study 
(or discussion) is not warranted.  It is the combination of many such 
studies that brings the big picture into focus.  In a time when science 
(parasitology?)  seems to becoming more and more reductionist, it is 
still necessary to incorporate some holistic approaches.
Enough "waxing philosophically" today (as a friend would say).
...that is another discussion for another day...

Brian Keas
keasbe9 at wfu.edu
Wake Forest University
Winston-Salem, NC 27109

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