Sleeping with eight eyes open: morphology, function, ecology and evolution of sleep in spiders

• Applicant: Dr. Daniela Rößler
• Subject Area: Sensory and Behavioural Biology ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 542896018

Sleep may be the most universal and yet least understood behavior in the animal kingdom. Despite decades of intensive research, we are still far from understanding the function, evolution, ecology and underlying mechanisms of sleep. While there is consensus on the universality of sleep in animals, rapid eye movement (REM) sleep—the sleep phase associated with most intense and narrative dreaming in humans—remains an enigma. REM sleep has so far only been established unambiguously in mammals, birds, reptiles as well as recently in cephalopods. The majority of sleep research is limited to traditional model species studied under laboratory conditions. Consequently, we are not yet capturing the full diversity of REM sleep expressions, and thus lack a deeper understanding of the origin and evolution of sleep components. The expansion of sleep research to challenge not only which species we study but also in what context, is a critical step towards a more comprehensive understanding of sleep. This research program will use spiders to enrich and expand our knowledge of the morphology, function, ecology, and evolution of sleep, particularly REM sleep. Crucially, it will develop two novel frameworks: (1) sleep in a comparative evolutionary framework, and (2) linking sleep and ecology. Sleep in spiders has been unstudied until my recent work including the discovery of a REM sleep-like state in jumping spiders. My subsequent research has revealed similar states across other spider families. REM sleep-like states in spiders seriously challenge the present view of REM sleep, its origin, function and evolution. Spiders display robust and distinct behavioral markers of sleep states and therefore represent exceptional models to systematically study sleep and to test REM sleep function, both in the lab and in the field. First, we will establish sleep and REM sleep in spiders. Second, we will explicitly study current proposed functions of sleep and REM sleep by testing the impact of sleep disruption on cognition, coordination and fitness. Third, we will record natural sleep in the field and test the influence of abiotic and biotic factors on sleep expression and behavior. Lastly, using key representatives of different spider families, we will link traits of sleep architecture, ecology, sensory modality as well as anatomy to an existing phylogenetic framework to reconstruct REM sleep evolution in spiders. Unprecedented in its phylogenetic depth and breadth, this research program will facilitate an unmatched understanding of how ecology and sensory makeup influence sleep, REM sleep, and their evolution. Ultimately this work will revolutionize how we study REM sleep by breaking open the field to the most diverse animal phylum on the planet, enabling a completely different scale of experimental investigation and comparative perspective.

• DFG Programme: Independent Junior Research Groups