Re: Chlorella NOT speciation. ?Contamination.

Glenn Morton (
Fri, 29 Nov 1996 17:42:39

James Mahaffy wrote:
>Glen in a recent post (Mon, 25 Nov 1996 19:27:26) cited "the change in
>family in a microscopic single celled creature which was observed to
>suddenly become a multicellular life form." In the post he refers to
>Talk Origins post of an alga, Chlorella pyrenoidosa (vulgaris) that
>changed its form to "being in the genus Coelosphaerium, which is in a
>different family from Chlorella" (Quote from Boxhorn). Sorry folks not
>everything, even on the venerable Talk Origins is good science, and this
>WOULD NOT be a good example to cite for speciation. It is not Glenn's
>fault (he can hardly be expected to know algae genera).

While I do not know algal species, I will accept full responsibility for
anything I erroneously report. Until I get a response from Boxhorn, I will
cease using this. I have used it before on the reflector with no prior
criticism. A couple of years ago, I had a couple of e-mail conversations with
Boxhorn about this thing. While I came away from that at the time re-assured
about this example, you have raised an excellent question. I would like
permission to forward your comments to Boxhorn

For information only, the abstract appears under a section "Bioluminescence,
Zooplankton Orientation and Growth," It is EOS vol 64 No. 52, Dec. 27, 1983.
p. 1102.
Here is the entire abstract.

Predator-mediated algal evolution in Chemostat culture Martin E.
Boraas (Center for Great Lakes Studies, University of Wisconsin
at Milwaukee, P.). 413, Milwaukee, Wi 53201)

"An unidentified microflagellate species (4-12 [mico]m) and
Chlorella Prenodosa (2-5 [micro]m) were grown at 25 C in
mixed-species chemostats with constant light and sterile,
inorganic medium flow. The flagellate readily consumed the algae
and grew rapidly (doubling time ca. 6 h). Size distributions of
both species are shown in the Figure (area = biovolume). After
an initial oscillation (curves 1,2), the system apparently
stabilized with both species coexisting. The algal population
now consisted of clusters of 4 to tens of cells that were immune
to predation by the flagellate (curve 3). The mean cluster size
then steadily decreased (curve 4) and stabilized at 4-8 cells
(curve 5). These, and other, observations support the
hypothesis: (1) a multicellular algal form was selected as a
response to predation pressures, (2) a minimum cluster size was
selected due to nutrient competition (large clusters have a
smaller surface area per unite biomass) and (3) genetic,
morphological, and structural diversity of the system increased
as a response to predation. Flagellate predation influences both
the genetics and the dynamics of microalgal population."
Boraas was the presider of this section when the talk was given.
So I presume he is no slouch in his field.

Is there anything in the abstract that is problematic?


Foundation,Fall and Flood