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Loss of coloniality by algae in culture

Robert Gensemer BGENSEMER at BIOLOGY.watstar.uwaterloo.ca
Sun Mar 7 12:32:46 EST 1993


In article <1nbp1jINN6js at uwm.edu> jboxhorn at csd4.csd.uwm.edu (Joseph E Boxhorn) writes:
>From: jboxhorn at csd4.csd.uwm.edu (Joseph E Boxhorn)
>Subject: Loss of coloniality by algae in culture
>Date: 7 Mar 1993 03:09:39 GMT
>	I have a few questions regarding algae in culture. I have been 
>culturing a number of freshwater phytoplankton species.  I have noticed that
>several colonial species seem to become unicellular in culture.  Examples of 
>this include Coelospherium and Gomphospherium.  Once cultured, they become
>almost indistinguishable from Chlorella.  I have noticed this effect in a 
>number of divisions and using several different culture media.
>
>	I have also noticed that in other colonial groups the number of cells
>per colony is reduced in culture.  Dinobryon is an example of a genus that does
>this.
>
>	1) Has anyone else seen this effect?

Interesting observations. I too have observed this repeatedly for 
_Asterionella_ cultures. Unless the cultures are growing logarithmically, or 
even in larger volume containers (eg. 500mL or better), I commonly get 
colony fragmentation.

>
>	2) Is anyone aware of any reviews or articles that discuss this?

I do not know of any, but would be interested to know about one.

>
>	3) Does anyone have an explanation?  (my own thoughts on this is that
>	   this is a response to the lack of predation in culture, but I
>	   haven't had a chance to run any experiments to test this.)

My own pet explanation invloves differences in physical forces _in vitro_ as 
compared to those in nature. At least for reasonably 2-D colonies like 
_Asterionella_, it doesn't seem to take much shear force to break up the 
colony. In chemostats that use air-bubling to mix, this is particularly 
problematic, and I often get most of the culture (even if growing well) 
existing as 2-celled colony fragments rather than the usual 8-celled 
colonies. Larger volume batch cultures (eg. 500 mL) that are gently stirred 
a few times a day seem to be the only kind of culture where the colonies are 
almost entirely intact. Of course, *lots* of chemical factors could also be 
involved but I suppose would be difficult to identify. Your lack of 
predation idea is interesting, but what would the mehcanism be...chemicals 
introduced by the predators, or direct tactile interaction?
-Bob

--
  Bob Gensemer                     BGENSEMER at BIOLOGY.watstar.uwaterloo.ca
  Department of Biology                
  University of Waterloo           Phone: (519) 885-1211, x-6408
  Waterloo, Ontario N2L 3G1        Fax: (519) 746-0614
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