Video analysis to investigate and compare ageing responses to temperature in four genotypes of Daphnia magna

Main supervisor: Yngvild Vindenes

Co-supervisors: ?ystein Langangen and Jan David Heuschele        

Note: This is the first of two proposed projects based on video analyses of trait responses in Daphnia magna. Data for two treatments are shared with the other project, and methods for video analysis may be developed in collaboration between the students. 

Background

Ageing (or senescence) can be defined as a late-life decline in organisms¡¯ performance, and is an important part of the life history for many species. It can be observed in various traits, including life history traits with direct consequences for fitness (survival, reproduction), behavioural traits (e.g. speed of movement), morphological traits (allometric relationships), and physiological traits (metabolic and developmental rates). In the currently warming world, there is a need for more knowledge on how ageing changes with temperature, in particular for ectotherms. It is not clear how the patterns of ageing change with temperature, or whether the same temperature-responses can be seen across different traits. Furthermore, we have little knowledge on whether ageing responses are similar for different genotypes. This requires detailed individual-level data of multiple traits throughout life, at different temperatures and genotypes. Repeated video measurements, available from previous work, provide a unique opportunity to obtain such data.

Study organism

The water flea Daphnia magna is a model organism for a range of questions in ecology and evolutionary biology. It has a wide distribution in freshwaters and brackish waters around the world, and is commonly found in small water bodies (rockpools, ponds). Its life history shows several adaptations to a highly variable and unpredictable environment, including resting stages that can remain dormant for decades and an altering sexual and asexual part of the life cycle. In the asexual part of the life cycle, D. magna reproduces clonally, which makes this organism ideal for experiments to separate out effects of environment and genotype.

Project description

We have available videos from a long-term experiment with the water flea Daphnia magna (see Vindenes et al 2025 for details on the experiment), providing a unique opportunity to study ageing in different traits and the temperature responses, in four different clonal lines (genotypes) originating from different locations (Morocco, Italy, and Sweden). The experiment was done with 240 individuals at six different temperatures across the temperature range of the species. Each individual was filmed multiple times (for 30 seconds each time) throughout its life from birth to death, providing a large set of videos which can be analysed with modern techniques for image analysis to measure various traits and how they change through life. So far, we have analysed the videos to obtain estimates of body length at different ages (Broch and Heuschele 2023, Vindenes et al. 2025), but not yet for other morphological measures (such as spine length relative to body length), or swimming behaviour (such as swimming speed or rotation), which are among focal traits to be studied in this project, that may be affected by ageing and will affect for example their ability to escape predators or aquire food.

The work in this master project will consist of analysing the videos based on image analysis methods (Cho et al. 2022, Broch and Heuschele 2023), to obtain a dataset of individual trait responses through life, across the six temperatures and four clonal lines. The student will further analyse this dataset using statistical models to investigate ageing in the different traits, and whether the responses differ between temperatures and clonal lines. More detailed hypotheses and study questions will be developed by the student depending on their specific interests, in collaboration with the project team. The project is suitable for a student who is interested in the general biology of ageing and temperature responses in ectotherms, who is comfortable working with programming and statistical analyses.

Sources

1. Broch, C., and J. Heuschele. 2023. Zoobooth: A portable, open-source and affordable approach for repeated size measurements of live individual zooplankton. Heliyon 9:e15383.
2. Cho, Y., R. A. Jonas-Closs, L. Y. Yampolsky, M. W. Kirschner, and L. Peshkin. 2022. Intelligent high-throughput intervention testing platform in Daphnia. Aging Cell 21:e13571.
3. Vindenes, Y., C. Broch, T. Andersen, D. O. Hessen, and T. Ergon. 2025. Understanding the role of ageing in the thermal responses of life history and fitness in Daphnia magna. Proceedings of the Royal Society B: Biological Sciences 292:20250430.