MitoCycle: Testing for habitat-dependent circadian and circatidal rhythms as possible metabolic adaptations to environmental fluctuations in marine bivalves

• Applicants: Dr. Christian Bock; Professorin Dr. Inna M. Sokolova; Professorin Dr. Kristin Tessmar-Raible
• Subject Area: Animal Physiology and Biochemistry
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 415984732

Environmental fluctuations present both challenges and opportunities for bioenergetics, requiring precise regulation of ATP production, biosynthetic intermediates, and signaling molecules. Mitochondria play a key role in this dynamic process, enabling organisms to optimize energy metabolism in response to changing conditions. Our previous work in the MitoBOX project revealed that mitochondrial adaptations are crucial for resilience to oxygen fluctuations in marine bivalves. We found that predictable intertidal oxygen regimes shape metabolic phenotypes, establishing strong links between mitochondrial function, organ performance - such as cardiovascular regulation - and whole-organism responses to environmental variability. However, the molecular mechanisms driving these interactions and the role of environmental fluctuations in metabolic rhythmicity remain poorly understood. This project seeks to bridge these critical knowledge gaps. We will investigate the metabolic rhythms of Mytilus edulis in response to tidal and diurnal environmental cycles, leveraging a novel integrative approach that examines metabolic regulation across multiple biological scales. By integrating transcriptomic, metabolomic, and mitochondrial analyses, we will assess how tidal versus atidal habitats influence metabolic rhythmicity, determine the persistence of these rhythms under constant laboratory conditions, and identify key environmental cues that entrain metabolic cycles. We hypothesize that: (1) metabolic phenotypes of M. edulis are governed by endogenous circadian and/or circatidal oscillations; (2) habitat-specific rhythms dominate, with circatidal rhythms in tidal mussels and circadian rhythms in atidal mussels; and (3) tidal environmental cues impose greater metabolic stress on atidal mussels than on tidal mussels. To test these hypotheses, we will investigate how habitat influences metabolic rhythmicity, whether these rhythms persist under controlled conditions, and how environmental factors - such as temperature, light, food availability, and air exposure - act as entrainment cues. Using mussels from tidal (North Sea) and atidal (Baltic Sea) environments, we will characterize metabolic phenotypic changes across natural and controlled conditions and assess the plasticity of metabolic rhythms in response to environmental cycles. By uncovering how M. edulis adapts its energy metabolism to rhythmic environmental changes, this study will advance our understanding of metabolic flexibility in fluctuating conditions and provide a mechanistic framework for assessing species resilience to environmental shifts, particularly in the face of climate change.

• DFG Programme: Research Grants