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J Chem Ecol

Title:		"beta-cyclocitral, a grazer defence signal unique to the cyanobacterium Microcystis"
Author(s):		Juttner F; Watson SB; von Elert E; Koster O;
Address:		"University of Zurich, Limnological Station, Kilchberg, Switzerland. juttner@limnol.uzh.ch"
Journal Title:		J Chem Ecol
Year:		2010
Volume:		20101112
Issue:		12
Page Number:		1387 - 1397
DOI:		10.1007/s10886-010-9877-0
ISSN/ISBN:		1573-1561 (Electronic) 0098-0331 (Linking)
Abstract:		"beta-Cyclocitral is often present in eutrophic waters and is a well known source of airborne and drinking water malodor, but its production and functional ecology are unresolved. This volatile organic compound (VOC) is derived from the catalytic breakdown of beta-carotene, and evidence indicates that it is produced by the activation of a specific carotene oxygenase by all species of the bloom-forming cyanobacterium Microcystis. Previous work has shown that beta-cyclocitral affects grazer behavior, but the nature of this interaction and its influence on predator-prey dynamics was unresolved. The present study combined analytical and behavioral studies to evaluate this interaction by using Microcystis NRC-1 and Daphnia magna. Results showed that beta-cyclocitral was undetectable in live Microcystis cells, or present only at extremely low concentrations (2.6 amol /cell). In contrast, cell rupture activated a rapid carotene oxygenase reaction, which produced high amounts (77 +/- 5.5 amol beta-cyclocitral/cell), corresponding to a calculated maximum intracellular concentration of 2.2 mM. The behavioral response of Daphnia magna to beta-cyclocitral was evaluated in a bbe(c) Daphnia toximeter, where beta-cyclocitral treatments induced a marked increase in swimming velocity. Acclimation took place within a few minutes, when Daphnia returned to normal swimming velocity while still exposed to beta-cyclocitral. The minimum VOC concentration (odor threshold) that elicited a significant grazer response was 750 nM beta-cyclocitral, some 2,900 times lower than the per capita yield of a growing Microcystis cell after activation. Under natural conditions, initial grazer-related or other mode of cell rupture would lead to the development of a robust beta-cyclocitral microzone around Microcystis colonies, thus acting as both a powerful repellent and signal of poor quality food to grazers"
Keywords:		Aldehydes/analysis/pharmacology Animals Carotenoids/analysis Daphnia/*drug effects/physiology Diterpenes/pharmacology Escape Reaction Feeding Behavior/drug effects Microcystis/*metabolism Odorants/analysis Swimming Vitamin A/analogs & derivatives beta-Car;
Notes:		"MedlineJuttner, Friedrich Watson, Susan B von Elert, Eric Koster, Oliver eng 2010/11/13 J Chem Ecol. 2010 Dec; 36(12):1387-97. doi: 10.1007/s10886-010-9877-0. Epub 2010 Nov 12"