{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T22:06:09Z","timestamp":1780956369699,"version":"3.54.1"},"reference-count":33,"publisher":"Cambridge University Press (CUP)","issue":"9","license":[{"start":{"date-parts":[[2011,7,15]],"date-time":"2011-07-15T00:00:00Z","timestamp":1310688000000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/www.cambridge.org\/core\/terms"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Parasitology"],"published-print":{"date-parts":[[2011,8]]},"abstract":"<jats:title>SUMMARY<\/jats:title><jats:p>For <jats:italic>Isospora<\/jats:italic> (Protozoa: Eimeriidae) parasites of passerine birds, diurnal periodicity of oocyst output is a well-described phenomenon. From the temporal zone to the tropics, oocyst production is correlated with the light-dark cycle, peaking in the afternoon hours. However, nothing is known about the existence of diurnal periodicity of these parasites in the birds of High Arctic environments, under permanent light during summer. We sampled free-ranging Snow Bunting (Aves: Passeriformes), on Svalbard in summer and tested oocysts output of <jats:italic>Isospora plectrophenaxia.<\/jats:italic> Here we show that under the permanent light conditions of Arctic summer in the wild, <jats:italic>Isospora plectrophenaxia<\/jats:italic>, a parasite of the Snow Bunting, still keeps the 24-h rhythm of oocyst output with the peak in the <jats:italic>post-meridiem<\/jats:italic> hours, despite the absence of diurnal periodicity in host's activity. Our findings prove the ability of avian <jats:italic>Isospora<\/jats:italic> to invoke alternative cues for synchronizing the circadian rhythms. Possible cues and adaptive significance of diurnal periodicity of parasite output in High Arctic are discussed. The maintenance of synchronization and timing of the parasite life-cycle stages is under positive selection pressure even in permanent daylight in the Arctic.<\/jats:p>","DOI":"10.1017\/s0031182011000795","type":"journal-article","created":{"date-parts":[[2011,7,15]],"date-time":"2011-07-15T09:07:22Z","timestamp":1310720842000},"page":"1077-1081","source":"Crossref","is-referenced-by-count":21,"title":["Keeping the clock set under the midnight sun: diurnal periodicity and synchrony of avian <i>Isospora<\/i> parasites cycle in the High Arctic"],"prefix":"10.1017","volume":"138","author":[{"given":"OLGA V.","family":"DOLNIK","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"BENJAMIN J.","family":"METZGER","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"MAARTEN J. J. E.","family":"LOONEN","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"56","published-online":{"date-parts":[[2011,7,15]]},"reference":[{"key":"S0031182011000795_ref31","first-page":"101","article-title":"Isospora, Caryospora and Eimeria (Apicomplexa: Eimeriidae) in passeriform birds from Czech Republic","volume":"33","author":"Svobodov\u00e1","year":"1994","journal-title":"Acta Protozoologica"},{"key":"S0031182011000795_ref30","doi-asserted-by":"publisher","DOI":"10.1081\/CBI-120026099"},{"key":"S0031182011000795_ref27","doi-asserted-by":"publisher","DOI":"10.1177\/074873099129000731"},{"key":"S0031182011000795_ref25","volume-title":"The Biology of the Coccidia","author":"Long","year":"1982"},{"key":"S0031182011000795_ref11","volume-title":"Handbook of the Birds of Europe, the Middle East and North Africa: The Birds of the Western Palearctic: Buntings and New World Warblers Vol. IX","author":"Cramp","year":"1994"},{"key":"S0031182011000795_ref5","unstructured":"Brandlmeier H. (2006). Die circadiane Ausscheidung von Kokzidienoozysten beim Haussperling (Passer domesticus) unter Ver\u00e4nderung des Melatoninspiegels: Experimentelle Untersuchungen am Modell eines Wirt-Parasit-Systems. Ph.D. thesis, University of Munich, Munich."},{"key":"S0031182011000795_ref3","doi-asserted-by":"publisher","DOI":"10.1016\/j.pt.2006.07.004"},{"key":"S0031182011000795_ref7","volume-title":"Perspectives in Parasitology: The Ecology and Diversity of Parasites","author":"Bush","year":"2001"},{"key":"S0031182011000795_ref9","doi-asserted-by":"publisher","DOI":"10.1111\/j.1600-079X.1991.tb00002.x"},{"key":"S0031182011000795_ref29","first-page":"263","article-title":"Die Coccidiose der Singvoegel. I. Der Ausscheidungsrhythmus der Isospora-Oocysten beim Haussperling (Passer domesticus)","volume":"178","author":"Schwalbach","year":"1960","journal-title":"Zentralblatt f\u00fcr Bakteriologie, Parasitenkunde, Infektionskrankheiten und Hygiene"},{"key":"S0031182011000795_ref20","doi-asserted-by":"publisher","DOI":"10.1007\/BF00383138"},{"key":"S0031182011000795_ref12","first-page":"113","article-title":"Diurnal periodicity in appearance of Isospora (Protozoa: Coccidea) oocysts from some passerine birds","volume":"281","author":"Dolnik","year":"1999","journal-title":"Proceedings of the Zoological Institute RAS"},{"key":"S0031182011000795_ref22","doi-asserted-by":"publisher","DOI":"10.1007\/BF01195761"},{"key":"S0031182011000795_ref6","volume-title":"The Physiological Clock","author":"B\u00fcnning","year":"1973"},{"key":"S0031182011000795_ref17","doi-asserted-by":"publisher","DOI":"10.1007\/BF00287430"},{"key":"S0031182011000795_ref2","doi-asserted-by":"publisher","DOI":"10.1007\/BF02433466"},{"key":"S0031182011000795_ref23","doi-asserted-by":"publisher","DOI":"10.1080\/09291010412331313287"},{"key":"S0031182011000795_ref18","doi-asserted-by":"publisher","DOI":"10.1051\/parasite\/1986612161"},{"key":"S0031182011000795_ref21","doi-asserted-by":"publisher","DOI":"10.1006\/gcen.2002.7776"},{"key":"S0031182011000795_ref13","unstructured":"Dolnik O. (2002). Some aspects of the biology and host-parasite interactions of Isospora spp. (Protozoa: Coccidiida) of passerine birds. Ph.D. thesis, University of Oldenburg, Oldenburg, Germany."},{"key":"S0031182011000795_ref24","doi-asserted-by":"publisher","DOI":"10.1645\/GE-1655.1"},{"key":"S0031182011000795_ref8","doi-asserted-by":"publisher","DOI":"10.1016\/j.yhbeh.2009.02.010"},{"key":"S0031182011000795_ref14","doi-asserted-by":"publisher","DOI":"10.1007\/s00436-006-0253-5"},{"key":"S0031182011000795_ref19","doi-asserted-by":"publisher","DOI":"10.1016\/S0361-9230(97)00224-4"},{"key":"S0031182011000795_ref4","first-page":"161","article-title":"Diurnal gametic periodicity in avian Isospora","volume":"33","author":"Boughton","year":"1933","journal-title":"American Journal of Hygiene"},{"key":"S0031182011000795_ref33","volume-title":"Environmental Physiology of Animals","author":"Willmer","year":"2005"},{"key":"S0031182011000795_ref26","doi-asserted-by":"publisher","DOI":"10.1016\/j.ijpara.2008.11.006"},{"key":"S0031182011000795_ref15","doi-asserted-by":"publisher","DOI":"10.5253\/078.098.0112"},{"key":"S0031182011000795_ref16","doi-asserted-by":"publisher","DOI":"10.1007\/s00436-007-0703-8"},{"key":"S0031182011000795_ref28","first-page":"431","article-title":"Untersuchungen und Beobachtungen an Coccidien der Gattungen Eimeria, Isospora und Caryospora bei V\u00f6geln mit einer Beschreibung von sechzehn neuen Arten","volume":"104","author":"Schwalbach","year":"1959","journal-title":"Archiv f\u00fcr Protistenkunde"},{"key":"S0031182011000795_ref32","unstructured":"Wild C. (2003). Experimentelle Untersuchung zur Chronobiologie einer Wirt-Parasit-Beziehung am Beispiel der Coccidiose (Isospora lacazei) des Haussperling (Passer domesticus). Ph.D. thesis, University of Munich, Munich, Germany."},{"key":"S0031182011000795_ref1","doi-asserted-by":"publisher","DOI":"10.1007\/s00436-008-1312-x"},{"key":"S0031182011000795_ref10","volume-title":"Parasitism. 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