Real-Life Lernaean Hydras: A Practical Activity about the Effects of Oxygen Concentration on Regenerative Capabilities of Planarians

Changes in environmental conditions can have a profound impact on organismal processes. For aquatic organisms, changes in dissolved oxygen concentration can have major repercussions, notably for physiological processes that have high long-term energetic costs and are more likely to rely on aerobic metabolic pathways. Here we propose a simple college or university-level low-cost laboratory activity that addresses the effect of differences in oxygen concentration on an important physiological property of planarian flatworms: their regeneration capacity. Students were asked to perform measurements and statistically compare the efficacy of the regeneration process between planarians kept in normoxic conditions and others kept in hypoxic conditions. The activity was evaluated by asking students to produce a short laboratory report with all of the sections that a scientific article generally comprises. This hands-on experiment has the benefit of going beyond how planarians are traditionally used in biodiversity classes (i.e. basic anatomy of flatworms) by combining behavioural, physiological and environmental observations while investigating the effects of an environmental variable on the regeneration response. We would further encourage professors to expand even more upon this framework by providing the students with an opportunity to actively engage in all steps inherent to the scientific process.