On 4 Apr 1995 CGE at CU.NIH.GOV wrote:
> Personally, I've always viewed commensalism as a benign form of
> parasitism in any case. This is in part because the same species can
> be a 'commensal' in one host and a 'parasite' in a different host
> (Zelmer definitions). An infection may also start out as 'commensal'
> but due to environmental or other factors become 'parasitic'. Is it
> worth having two rigid terms to describe what may be transient
> conditions?
As I alluded to earlier, I don't believe in commensals. They could only occur
in the strictest sense, if an infection provided the host with some benefit
that exactly counteracted the negative of the infection. The condition,
therefore would not be transient. A parasite, no matter how benign, is
not a commensal.
> Perhaps the definition of a parasite
> should be: a eukaryote living in or on another eukaryote on which it
> is dependent and from which it derives nutritional benefits. Unless
> you WANT to include bacteria and viruses of course.
I'd even include prions...but then again, I'm not fussy. The only reason
I could use to justify seperating the prokaryotes is their replication in
definitive hosts, but this is characteristic of some eukaryotes as well.
> My list of commensals/parasites would probably be very
> similar to Derek's ecto-/endo-symbionts.
y list of symbionts includes parasites, but is a much longer list.
Derek Zelmer
