Ciliate, morphogenesis, taxonomy

Peter Eigner p.eigner at magnet.at
Mon Feb 27 16:37:00 EST 1995


    Hi, 
    I just wonder if there is anybody who is interested in the taxonomy and
phylogeny of hypotrich ciliates investigated with the help of protargol
impregnation.
   For some years I have been trying to find out about the relationships
within the hypotrichs by investigating processes during divisional
morphogenesis. It shows now that understanding the morphogenesis of these
complex and highly differentiated ciliates is essential for defining species
and establishing higher taxa in a natural system. For example, cortical
structures in interphase (ÒadultÒ) cells that seem to be homologous in 2
species (of 1 genus) turn out to be of completely different origins and thus
belong to different families (this is just one of the traps which becomes
evident watching morphogenesis; [cp. J. Euk. Microbiol., 41(3), 1994, pp.
243-261]. Moreover, by observing morphogeneses we are supplied with many
additional distinctive taxonomic features (e. g. migration of cirral rows).
    Reading and interpreting detailed descriptions of morphogeneses written
by many different authors is rather time-consuming. In order to make
character analyzing much easier I developed a way of making computer graphics
to show three important groups of characters in one drawing: 1. the complete
interphase ciliature, 2. its morphogenetic origin and 3. processes during
morphogenesis. These pictures (one for each species) laid side by side makes
it much easier to recognize relationships, since one has now interphase and
morphogenetic characters at one look.
   I used some computer graphics of this kind in a paper I just finished
[Europ. J. Protistol., in press] to redefine the Kahliellidae (a hypotrich
family) and I am using them for a paper I just work on dealing with all
detailed descriptions of hypotrich morphogeneses (there are about 150 more or
less detailed descriptions available now).
   Questions that arise when analyzing morphogenetic processes and characters
are, e. g. the questions of their priority and in which direction
evolutionary changes (transformation lines) in a certain character are to be
read: it is a common view for instance, that a reduced number of cirri in
hypotrichs represents a higher evolved state; but, to make things not too
easy, there are species which have a reduced ventral and an increased dorsal
infraciliature. However, the chronological order in which cortical structures
are generated and rebuilt during morphogenesis has in my view something to do
with the order in which they were originally formed by evolution. This gives
us some hints about priority of characters and direction of transformation
lines. Furthermore, there is one middle stage during morphogenesis before
migration begins which, I believe, most likely mirrors the appearance of an
ancestor of this species, allowing us a glimpse into the past of evolution.
Finally, if a cortical structure, e. g. a dorsal kinety or a cirral row
develops de novo during morphogenesis, i. e. something new develops in an
ÒemptyÒ place on the cellÔs surface, does this mean the organism ÒremembersÒ
a lost kinety or row from an ancestor, or does it mean it forms something
completely new (adaptive character).
       
Peter Eigner
Schroetten 22
A-8483 Deutsch Goritz
Austria
phone/fax: 034747192
e-mail: p.eigner at magnet.at



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