TY  - JOUR
A1  - Joschinski, Jens
A1  - Beer, Katharina
A1  - Helfrich-Förster, Charlotte
A1  - Krauss, Jochen
T1  - Pea Aphids (Hemiptera: Aphididae) Have Diurnal Rhythms When Raised Independently of a Host Plant
JF  - Journal of Insect Science
N2  - Seasonal timing is assumed to involve the circadian clock, an endogenous mechanism to track time and measure day length. Some debate persists, however, and aphids were among the first organisms for which circadian clock involvement was questioned. Inferences about links to phenology are problematic, as the clock itself is little investigated in aphids. For instance, it is unknown whether aphids possess diurnal rhythms at all. Possibly, the close interaction with host plants prevents independent measurements of rhythmicity. We reared the pea aphid Acyrthosiphon pisum (Harris) on an artificial diet, and recorded survival, moulting, and honeydew excretion. Despite their plant-dependent life style, aphids were independently rhythmic under light–dark conditions. This first demonstration of diurnal aphid rhythms shows that aphids do not simply track the host plant’s rhythmicity.
KW  - artificial diet
KW  - circadian clock
KW  - hourglass clock
KW  - Acyrthosiphon pisum
KW  - photoperiodism
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-168783
VL  - 16
IS  - 1
ER  - 
TY  - JOUR
A1  - Beer, Katharina
A1  - Joschinski, Jens
A1  - Sastre, Alazne Arrazola
A1  - Krauss, Jochen
A1  - Helfrich-Förster, Charlotte
T1  - A damping circadian clock drives weak oscillations in metabolism and locomotor activity of aphids (Acyrthosiphon pisum)
JF  - Scientific Reports
N2  - Timing seasonal events, like reproduction or diapause, is crucial for the survival of many species. Global change causes phenologies worldwide to shift, which requires a mechanistic explanation of seasonal time measurement. Day length (photoperiod) is a reliable indicator of winter arrival, but it remains unclear how exactly species measure day length. A reference for time of day could be provided by a circadian clock, by an hourglass clock, or, as some newer models suggest, by a damped circadian clock. However, damping of clock outputs has so far been rarely observed. To study putative clock outputs of Acyrthosiphon pisum aphids, we raised individual nymphs on coloured artificial diet, and measured rhythms in metabolic activity in light-dark illumination cycles of 16:08 hours (LD) and constant conditions (DD). In addition, we kept individuals in a novel monitoring setup and measured locomotor activity. We found that A. pisum is day-active in LD, potentially with a bimodal distribution. In constant darkness rhythmicity of locomotor behaviour persisted in some individuals, but patterns were mostly complex with several predominant periods. Metabolic activity, on the other hand, damped quickly. A damped circadian clock, potentially driven by multiple oscillator populations, is the most likely explanation of our results.
KW  - circadian mechanisms
KW  - behavioural ecology
KW  - damped circadian clock
KW  - Acyrthosiphon pisum
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170020
VL  - 7
IS  - 14906
ER  -