CONTENT - International Society of Zoological Sciences

S8-9 ICZ2008 - Abstracts
Biodiversity and ecology of freshwater ciliates
Thomas Weisse
Institute for Limnology of the Austrian Academy of Sciences,
Mondseestr. 9, Mondsee, A-5310, Austria
Ciliates are abundant, diverse and quantitatively important players in
freshwater food webs. Their quantitative significance as consumers
of protist and bacterial production, and food for larger metazoans
such as Daphnia and copepods was recognized mainly during the
1980s and early 1990s. Biogeography and biodiversity of ciliates has
been controversially discussed during the past decade. The
speculation that ciliates and other free-living protists are
cosmopolitans, found everywhere where a suitable habitat exists,
without any geographic isolation provoked intensive field and
laboratory studies to demonstrate that ciliates do have a
biogeography. Detailed taxonomic research by a few specialists
revealed that, while many species are globally dispersed, endemics
are also common among soil and freshwater ciliates. With the advent
of molecular techniques to identify and classify ciliates based upon
their genes it became obvious that ciliate diversity is considerably
larger than derived from morphology-based alpha-taxonomy.
Similarly, ecophysiological laboratory experiments revealed large
inter- and even intraspecific differences. The response to food,
temperature, pH and predators has been identified as the major
environmental factors controlling the occurrence and distribution of
freshwater ciliates. It now appears that ecotypes, adapted to a
particular habitat, are common among widespread ciliates.
Measurements of the actual rates of dispersal and the frequency of
sexual reproduction in the field are currently the major challenges for
a better understanding of the biodiversity of freshwater ciliates.
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