Differences in osmotolerance in freshwater and brackish water populations of Theodoxus fluviatilis (Gastropoda: Neritidae) are associated with differential protein expression |
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Authors: | Frauke Symanowski Jan-Peter Hildebrandt |
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Institution: | 2. Leibniz-Institut für Meereswissenschaften, Benthos?kologie, Düsternbrooker Weg 20, 24105, Kiel, Germany 1. Animal Physiology and Biochemistry, Zoological Institute, Ernst Moritz Arndt-University, Biotechnikum, Walther Rathenau-Strasse 49 a, 17489, Greifswald, Germany
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Abstract: | The euryhaline gastropod Theodoxus fluviatilis is found in northern Germany in freshwater or in brackish water habitats in the Baltic Sea. Previous studies have revealed
that individuals from both habitats are not distinguishable by morphological characters or by sequence comparison of DNA encoding
16S RNA or cytochrome C. As reported in this study, animals collected in the two habitats differ substantially in their physiological
ability to adapt to different salinities. Comparison of accumulation rates of ninhydrin-positive substances (NPS) in foot
muscle upon transfer of animals to higher medium salinities revealed that brackish water animals were perfectly able to mobilize
NPS, while freshwater animals had only limited ability to do so. In an attempt to explore whether this difference in physiology
may be caused by genetic differentiation, we compared protein expression patterns of soluble foot muscle proteins using 2D
gel electrophoresis and silver staining. Of the 40 consistently detected protein spots, 27 showed similar levels in protein
expression in animals collected from freshwater or brackish water habitats, respectively. In 12 spots, however, protein concentration
was higher in brackish water than in freshwater animals. In four of these spots, expression levels followed increases or decreases
in medium salinities. In a different set of 4 of these 12 spots, protein levels were always higher in brackish water as compared
to freshwater animals, regardless of their physiological situation (14 days in artificial pond water or in medium with a salinity
of 16‰). The remaining 4 of the 12 spots had complex expression patterns. Protein levels of the remaining single spot were
generally higher in freshwater animals than in brackish water animals. These expression patterns may indicate that freshwater
and brackish water animals of T. fluviatilis belong to different locally adapted populations with subtle genetic differentiation. |
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