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
>> 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
>> 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 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