commensalism

[ersatz-read.livejournal.com]

commensalism, noun.  A symbiotic relationship between two organisms where one benefits while the other is unaffected.  An organism participating in such a relationship is called a commensal.

The three general types of persistent biological interactions are mutualism (both organisms benefit), parasitism (one benefits at the expense of the other), and commensalism.

Etymology:  Latin for "sharing a table", from com (together) + mensa (table).  The use of the word in biology began around 1870, but the use of 'commensal' as "one who eats at the same table" began in the 1400s. 

The recent Scientific American article "The Ultimate Social Network" by Jennifer Ackerman discusses how babies are colonized at birth:  "Each individual acquires his or her own community of commensals...from the surrounding environment.  Because the womb does not normally contain bacteria, newborns begin life as sterile, singular beings.  But as they pass through the birth canal, they pick up some of Mom's commensal cells, which then begin to multiply."  Some of these bacteria can help the newborn to digest milk.

From Fraser's Magazine for Town and Country, volume 30 (1844), a section on desserts, fruits, sweetmeats, and liqueurs:  "...we can for the life of us see no harm in talking for half-an-hour with you, gentle reader, on those commensal pleasures common to us both, which begin the earliest, and finish the latest, in this wicked world which we call ours."

Comments

[theidolhands.livejournal.com]

Interesting word, I can think of times in my life when someone thought their parasitic relationship was actually commensalist (it seems being at the beneficiary end can sometimes result in obliviousness, if not willful obtuseness).

[ersatz-read.livejournal.com]

Been there; have the disfiguring scars to prove it.

[prettygoodword.livejournal.com]

So the spectrum is mutualism > commensalism > parasitism?

---L.

[ersatz-read.livejournal.com]

I guess. But it seems like it should take more than one dimension to describe the relationships between organisms. For example, in an NPR interview Ms. Ackerman described helicobacter pylori: it's a factor in ulcer formation in some people, yet it also plays a role in regulating weight. Due to modern medical practices, the bacteria is becoming less common, which may have a hand in increased levels of obesity, and all the medical problems that go with it.

That isn't just parasitism, because in some people the bacteria plays a crucial role, without causing ulcers. But it isn't mutualism either, because of the people who _do_ develop ulcers. That's my take, anyway. I don't know if there's a word for symbiosis where the relationship is complex and situational.