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Diploma thesis
Energetic costs of swimming in two cyprinid fishes:
carp (Cyprinus carpio L.) and roach (Rutilus rutilus (L.))
Tutor: Dr. Franz Hölker and Dr. Georg Staaks
Energetic costs of locomotion arise from muscle activity to generate movements. The required energy is mobilized by combustion of high-energy substrates. Therefore, the amount of oxygen consumed during activity by an animal is a measure of the energy expenditure during locomotion. The oxygen consumption of a fish swimming at different velocities can be determined with an intermittent-flow respirometer.
In my diploma thesis I studied the energy expenditure during swimming in carp and roach of various masses at different swimming speeds. Based on these data the relationship of active metabolic rate, swimming velocity and body mass was calculated and models were derived that allow the estimation of energetic costs of an active fish at any swimming speed. Moreover, I introduced a morphometrical factor which is directly proportional to the drag on a swimming fish to evaluate the influence of body shape on swimming costs.
Ph D thesis
Sympatric speciation along ecological gradients -
a case study on ciscoes in Lake Stechlin, Germany:
Coregonus albula and Coregonus fontanae
Tutor: Dr. Franz Hölker and Dr. Georg Staaks
My Ph D thesis deals with the ecological segregation and sympatric speciation of ciscoes in lake Stechlin, Germany. My goal is to identify the mechanisms of this diversifying process by means of ecophysiological parameters. The autumn-spawning Coregonus albula (L.) is the most abundant fish species in the lake, living in sympatry with the endemic spring-spawning Coregonus fontanae (Schulz & Freyhof). Ecological segregation has been shown with respect to the vertical distribution within the pelagic habitat of these planktivorous fish, but other differences between the species are not known. The habitat of these ciscoes is predominantly defined by the environmental factors temperature, light and zooplankton density, which decline continuously with depth. Ecophysiological analyses will be carried out to sheds light on the question, which functional characteristics and adaptations enable the co-existence of the species despite high interspecific competition. Moreover, statements about the stability and potential risks for the species due to environmental changes become assessable on the basis of these insights.
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PhD:
Ohlberger, J., Staaks, G., Petzoldt, T., Mehner, T., & Hölker, F. (submitted). Physiological specialization by thermal adaptation drives ecological divergence in a sympatric fish species pair. Evolutionary Ecology Research
Ohlberger, J., Mehner, T., Staaks, G., & Hölker, F. (accepted). Is ecological segregation in a sympatric species pair of coregonines supported by divergent feeding efficiencies? Canadian Journal of Fisheries and Aquatic Sciences
DOI: 10.1139/F08-120
Ohlberger, J., Mehner, T., Staaks, G., & Hölker, F. (2008) Temperature-related physiological adaptations promote ecological divergence in a sympatric species pair of temperate freshwater fish, Coregonus spp. Functional Ecology 22, 501-508
DOI: 10.1111/j.1365-2435.2008.01391.x
Ohlberger, J., Staaks, G., & Hölker, F. (2007) Effects of temperature, swimming speed and body mass on standard and active metabolic rate in vendace (Coregonus albula). Journal of Comparative Physiology B 177, 905-916.
DOI: 10.1007/s00360-007-0189-9
Diploma:
Ohlberger, J., Staaks, G., & Hölker, F. (2007) Estimating the active metabolic rate (AMR) in fish based on tail beat frequency (TBF) and body mass. Journal of Experimental Zoology 307A, 296-300.
DOI: 10.1002/jez.384
Ohlberger, J., Staaks, G., & Hölker, F. (2006) Swimming efficiency and the influence of morphology on swimming costs in fishes. Journal of Comparative Physiology B 176, 17-25.
DOI: 10.1007/s00360-005-0024-0
Ohlberger, J., Staaks, G., van Dijk, P.L.M., & Hölker, F. (2005) Modelling energetic costs of fish swimming. Journal of Experimental Zoology 303A, 657-664.
DOI: 10.1002/jez.a.181
Undergraduate research project:
Gallo, V.P., Accordi, F., Ohlberger, J., & Civinini, A. (2004) The chromaffin system of the beluga sturgeon Huso huso (Chondrostei): histological, immunohistochemical and ultrastructural study. Italian Journal of Zoology 71, 279-285.
Conferences:
Ohlberger, J. (2008) Physiological specialization by thermal adaptation promotes ecophysiological divergence in a sympatric fish species pair. ‘Fourth International Conference in Africa for Comparative Physiology & Biochemistry’ (19-25 July 2008) at Maasai Mara National Reserve, Kenya.
Poster:
Ohlberger, J. (2007) Sympatric ecological speciation associated with physiological adaptation to environmental temperature in a species pair of temperate freshwater fish. ALTER-Net Summer School "Trends in Biodiversity: European Ecosystems and Policy" (1-13 September 2007) in Peyresq, France
Ohlberger, J. (2007) Sympatric speciation along ecological gradients - a case study on ciscoes in Lake Stechlin: Coregonus albula and Coregonus fontanae. Postgraduate summer school “Understanding Global Environmental Change” (18-24 May 2007) at Wageningen University, the Netherlands
For questions regarding electronic reprints please mail to: Ohlberger@igb-berlin.de
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