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How did the last common ancestor of the hypotrichs
(Ciliophora, Spirotricha) look like?
Helmut Berger
Consulting Engineering Office for Ecology, Salzburg, Austria
The Hypotricha Stein (= Stichotrichia Small & Lynn) are a major
group of the spirotrichs. The knowledge of the ground-pattern (=
ground-plan) of an evolutionary unit is of fundamental importance for
the establishment of a phylogenetic system. This pattern is the combination
of all features (e.g., morphological, ontogenetic, ecological,
molecular) of the last common ancestor (stem-species) from which a
monophylum evolved, that is, it is summary of apomorphies and
more or less young plesiomorphies. Some supposed apomorphies of
the Hypotricha are: (1) 18 frontal-ventral-transverse cirri; (2) three
dorsal kineties; (3) parental somatic ciliature completely replaced
during cell division. Some plesiomorphies of the hypotrichs are: (1)
cirri present; (2) body dorsoventrally flattened; (3) body flexible; (4)
frontal-ventral-transverse cirri originate from six anlagen; (5) caudal
cirri present; (6) cortical granules present; (7) lack of kinetodesmal
fibres in interphasic specimens; (8) benthic; (9) telomeric repeat
sequence TTTTGGGG. For details, see Monographs of hypotrichs by
Berger (1999; Monographiae Biol. 78:1–1080; oxytrichids), Berger
(2006; Monographiae Biol. 85: 1–1303; urostyloids), and Berger
(2008; Monographiae Biol., in press; amphisiellids). The financial
support of the Austrian Science Fund (FWF; Project P-20569-B17) is
greatly acknowledged.
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