{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,26]],"date-time":"2026-10-26T19:38:08Z","timestamp":1793043488154,"version":"4.5.0"},"reference-count":72,"publisher":"National Academy of Sciences","issue":"45","license":[{"start":{"date-parts":[[2026,10,26]],"date-time":"2026-10-26T00:00:00Z","timestamp":1792972800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","award":["542896018"],"award-info":[{"award-number":["542896018"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[2026,11,10]]},"abstract":"<jats:p>\n                    Sleep is a fundamental behavioral state found across the animal kingdom, yet most of what we know about sleep is heavily vertebrate-biased. Studies are scarce or nonexistent in all but a few invertebrate lineages. A recent study of an REM sleep-like behavior in a jumping spider has reported unexpected parallels to sleep expression in vertebrates. So far, experimental evidence that these behavioral indicators truly represent sleep was lacking in spiders. Here, we present a comprehensive investigation into sleep behavior in the spider\n                    <jats:italic toggle=\"yes\">Portia fimbriata<\/jats:italic>\n                    (Salticidae). We demonstrate diurnal activity, a free-running circadian rhythm, robust sleep architecture, regularly occurring REM-like behaviors, elevated arousal thresholds during those REM-like states, as well as rebound effects following sleep disruption. We conclude that the behavior we observe in spiders is behavioral sleep, providing evidence for an REM-like sleep substate in a terrestrial invertebrate. These results contribute to fundamental questions about the evolution and function of sleep across animals.\n                  <\/jats:p>","DOI":"10.1073\/pnas.2618030123","type":"journal-article","created":{"date-parts":[[2026,10,26]],"date-time":"2026-10-26T19:06:31Z","timestamp":1793041591000},"update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":0,"title":["Behavioral evidence for two-stage sleep in spiders"],"prefix":"10.1073","volume":"123","author":[{"ORCID":"https:\/\/orcid.org\/0009-0008-1869-4959","authenticated-orcid":false,"given":"Nadja","family":"Geiger","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/041nas322","id-type":"ROR","asserted-by":"publisher"}],"name":"Section II Animal Diversity, Bonn Institute for Organismic Biology, University of Bonn","place":["Bonn 53121, 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Konstanz","place":["Konstanz, Germany"]},{"id":[{"id":"https:\/\/ror.org\/0546hnb39","id-type":"ROR","asserted-by":"publisher"}],"name":"Zukunftskolleg, University of Konstanz","place":["Konstanz, Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Massimo","family":"De Agr\u00f2","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05trd4x28","id-type":"ROR","asserted-by":"publisher"}],"name":"Center for Mind\/Brain Sciences, University of Trento","place":["Rovereto, Italy"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Barrett A.","family":"Klein","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/00x8ccz20","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Biology, University of Wisconsin-La Crosse","place":["La Crosse"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4678-2231","authenticated-orcid":false,"given":"Daniela 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