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  - Joschinski, Jens
A1  - Hovestadt, Thomas
A1  - Krauss, Jochen
T1  - Coping with shorter days: do phenology shifts constrain aphid fitness?
JF  - PeerJ
N2  - Climate change can alter the phenology of organisms. It may thus lead seasonal organisms to face different day lengths than in the past, and the fitness consequences of these changes are as yet unclear. To study such effects, we used the pea aphid Acyrthosiphon pisum as a model organism, as it has obligately asexual clones which can be used to study day length effects without eliciting a seasonal response. We recorded life-history traits under short and long days, both with two realistic temperature cycles with means differing by 2 °C. In addition, we measured the population growth of aphids on their host plant Pisum sativum. We show that short days reduce fecundity and the length of the reproductive period of aphids. Nevertheless, this does not translate into differences at the population level because the observed fitness costs only become apparent late in the individual's life. As expected, warm temperature shortens the development time by 0.7 days/°C, leading to faster generation times. We found no interaction of temperature and day length. We conclude that day length changes cause only relatively mild costs, which may not decelerate the increase in pest status due to climate change.
KW  - Homoptera aphididae
KW  - clock reproduction ecology
KW  - phenotypic plasticity
KW  - phenology shifts
KW  - insect timing
KW  - physiological constraints
KW  - day length
KW  - circadian rhythms
KW  - Acyrthosiphon pisum
KW  - climate change
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-148382
VL  - 3
IS  - e1103
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  -