Related Experiment Videos
Evolution of circadian organization in vertebrates
M Menaker1, L F Moreira, G Tosini
1NSF Center for Biological Timing, University of Virginia, Charlottesville 22903, USA. mm7e@virginia.edu
Summary
Vertebrate circadian systems exhibit diverse organization, with a core "circadian axis" present in all species. Evolutionary factors, like a "nocturnal bottleneck" in early mammals, help explain some observed differences in circadian rhythms.
Area of Science:
- Chronobiology
- Evolutionary Biology
- Comparative Physiology
Background:
- Circadian organization describes the physical structure and interaction principles of the circadian system, producing physiological and behavioral rhythms.
- Understanding circadian organization and its evolution is crucial for both basic science and practical applications.
- Significant diversity exists in vertebrate circadian organization, posing challenges for generalization.
Purpose of the Study:
- To explore the diversity in vertebrate circadian organization.
- To understand the evolutionary principles underlying these differences.
- To identify factors contributing to phylogenetically "incoherent" diversity.
Main Methods:
- Review of existing literature on vertebrate circadian systems.
- Phylogenetic analysis of circadian organization traits.
- Hypothesizing evolutionary scenarios, such as the "nocturnal bottleneck".
Main Results:
- Identified a conserved "circadian axis" (retinas, pineal gland, suprachiasmatic nucleus) across all vertebrates.
- Noted that in non-mammalian vertebrates, the pineal gland acts as a photoreceptor and oscillator, and extraretinal photoreceptors are present.
- Mammals lack these non-retinal photoreceptive roles of the pineal gland and extraretinal photoreceptors.
Conclusions:
- The evolution of circadian organization in vertebrates is complex, with both clear phylogenetic patterns and "phylogenetically incoherent" diversity.
- The "nocturnal bottleneck" hypothesis offers a potential explanation for differences between mammals and other vertebrates.
- Further research is needed to fully elucidate the evolutionary trajectory of vertebrate circadian systems.