The present book is a monograph about two groups of hypotrichous
ciliates, namely the Amphisiellidae and the Trachelostylidae. It is the
third of six volumes which - view the Hypotricha, one of the three major
taxa of the spirotrichs. The first volume is about the Oxytrichidae, a
rather large group, many species of which have 18 highly
characteristically arranged frontal-ventral-transverse cirri and, much
more importantly, a comparatively complex dorsal ciliature due to
(oxytrichid) fragmen- tion of dorsal kineties during cell division
(Berger 1999). The second volume deals with the Urostyloidea, which are
characterised by a zigzag-arrangement of the ventral cirri (Berger
2006). Although this pattern is often very impressive, it is a
relatively simple feature originating by a more or less distinct
increase of the number of frontal-ventral-transverse cirri anlagen.
These anlagen produce cirral pairs which are serially arranged in
non-dividing specimens. Some - ers are likely astonished that the
monograph on urostyloids does not include Urol- tus, a group of tailed
species, which also have a distinct zigzagging cirral pattern. However,
morphological and molecular data indicate that the zigzag pattern of U-
leptus evolved independently, that is, convergently to that of the
urostyloids. Thus, Uroleptus was excluded from the urostyloid review. A
zigzag pattern is also known from some oxytrichids, for example,
Neokeronopsis, Territricha, Pattersoniella, showing that this pattern
evolved several times independently (Berger 1999, 2006, Foissner et al.
2004).
