Supervisor: prof. dr. hab. Marcin Czarnołęski (marcin.czarnoleski@uj.edu.pl)

Institute of Environmental Sciences

Background information:

The evolution of different body sizes and body plans has been linked to changes in cell size. Despite the fundamental importance of cell size for organ function in the body, the origin of cell size variation between organisms (individuals, sexes, populations, species) is not well understood. According to the theory of optimal cell size (TOCS), cell size is optimised as an adaptation to the environmental context. Central to this theory are the costs and benefits of cell size. Smaller cells have a high capacity to process resources, such as nutrients and oxygen, due to their larger surface-to-volume ratio and shorter intracellular distances. The same principle explains why larger cells are more energy efficient, as a smaller surface area reduces the cost of maintaining the ion gradient across cell membranes. These benefits and costs of cell size should be balanced differently, depending on metabolic demand and resource supply, and thus on environmental conditions. This theory requires further development and empirical testing.

The main question to be addressed in the project:

To what extent does cell size differentiation between organisms occur through systemic and coordinated changes throughout the organism? Or do only certain cell types change, while other tissue types remain unchanged by evolutionary processes? When organisms evolve differences in cell size or respond developmentally to environmental conditions (oxygen, temperature) by changing cell size, do such changes in cell size have consequences for environmental functioning? In the case of ectotherms, do forms with small cells outcompete forms with large cells under warm and hypoxic conditions?

Information on the methods/description of work:

In laboratory experiments and comparative studies, we will conveniently use different models to study differences in cell size, which will include forms of the fruit fly (Drosophila melanogaster) with differences in cell size generated by natural evolutionary processes or environmental developmental conditions, as well as different insect taxa with well-defined phylogenetic relationships (across-species comparative data). We will study cell size in different tissue types to characterise phenotypes/genotypes. For cell size fly variants, will perform laboratory experiments with environmental gradients (oxygen, temperature, food availability) to measure different types of physiological performance (e.g. flight, metabolic rate, life history traits) in order to relate physiological performance and life history traits to cell size.

Additional information (e.g Special requirements from the student):

Required: (1) Master's level in a field related to the scope of the project; (2) university level knowledge of ecology, evolution and physiology; (3) general experience and interest in any area of ecology and evolution; (4) basic knowledge of statistics; (5) fluency in English.

Preferred: (1) experience with more complex statistical models (especially in R); (2) experience with physiological measurements, histological methods and/or keeping small invertebrates in the laboratory.

Personality traits: (1) effective communication; (2) interpersonal skills and ability to work well with others; (3) computer literacy and technical skills; (4) problem-solving/creativity; (5) planning and organisational skills; (6) high degree of motivation; (7) reliability, conscientiousness and punctuality; (8) ability to critically evaluate the results obtained; and (9) willingness to actively participate in conferences, festivals and other forms of dissemination of project results and to prepare scientific publications in English at a high international level.

Place/name of potential foreign collaborator:

Prof. W.C.E.P. Verberk, Radboud University, Nijmegen, Netherlands

References:

[1] Privalova, V., Sobczyk, Ł., Szlachcic, E., Labecka, A.M., Czarnoleski, M. (2024). Heat tolerance in Drosophila melanogaster is influenced by oxygen conditions and mutations in cell size control pathways. Philosophical Transactions of the Royal Society B, 379, 20220490.

[2] Schramm, B.W., Labecka, A.M., Gudowska, A., Antoł, A., Sikorska, A., Szabla, N., Bauchinger, U., Kozlowski, J., Czarnoleski, M. (2021). Concerted evolution of body mass, cell size and metabolic rate among carabid beetles. Journal of Insect Physiology, 132, 104272.

[3] Verberk, W.C.E.P., Sandker, J.F., van de Pol, I.L.E., Urbina, M.A., Wilson, R.W., McKenzie, D.J., Leiva, F.P. (2022). Body mass and cell size shape the tolerance of fishes to low oxygen in a temperature-dependent manner. Global Change Biology, 28, 5695–5707.