Seeing and (not) being seen:
Sensory ecology of the blue-tailed damselfly Ischnura elegans
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1
Lund University, Department of Biology, Sweden
Adult blue-tailed damselflies (Ischnura elegans) are colourful insects. Males turn bright green after emergence and become blue over the days. Females show a red or purple colouration first and, when sexually mature, either mimic the blue colour of the males or are camouflaged by an inconspicuous olive-green or brown. In the past, the mating system and the underlying genetics and population ecology of I. elegans have been studied intensively. However, the sensory basis of their colour polymorphism for (1) intraspecific and (2) predator-prey interactions have not been explored. We quantified backgrounds in the natural habitat and the body colouration of the damselflies by spectral reflectance measurements, including time series documenting the animals' colour change. (1) To understand the function of the colours for mate and rival detection, we determined the angular, spectral and polarization sensitivity of photoreceptors in the compound eyes of males. Four spectral types of receptors maximally sensitive in the UV (370 nm), blue (440 nm), green (540 nm) and red (600 nm) region of the spectrum were found by intracellular recordings (Fig. 1). The sensitivity curve of the red receptor is narrower than an opsin template indicating spectral filtering, likely by the green receptor. Combining spectral reflectance and spectral sensitivity data in a model enables us to reconstruct the saliency of the different colour morphs to conspecific males searching for mates or trying to chase off rivals. (2) The functions of the colours for predator avoidance are also largely unknown. In similar models, we therefore incorporate known spectral sensitivities of passerines, potential predators on I. elegans. This allows us to judge which colour morphs are best camouflaged for the birds. Our goal is a physiologically based understanding of the reasons for colour polymorphism, a common phenomenon in damselflies.
Acknowledgements
This research was funded by the Swedish Research Council, the Tryggers Foundation and the Swiss National Science Foundation. We thank E. Kreiss for a kind introduction to electrophysiology, R. Petie, E. Warrant, D.-E. Nilsson and D. O’Carroll for help with the setup, M. Kinoshita and B. el Jundi for valuable instructions on the preparation method, T. Labhart for expert advice on the recording protocol and W. Sidemo-Holm, C. Sollevi, A. Nordén, L. Orr and E. Svensson for help in the field.
Keywords:
Colour vision,
polarization vision,
angular sensitivity,
spectral reflectance,
colour change,
colour polymorphism,
odonata,
Damselfly,
Ischnura elegans
Conference:
International Conference on Invertebrate Vision, Fjälkinge, Sweden, 1 Aug - 8 Aug, 2013.
Presentation Type:
Oral presentation preferred
Topic:
Colour and polarisation vision
Citation:
Henze
MJ,
Lind
O,
Kohler
M and
Kelber
A
(2019). Seeing and (not) being seen:
Sensory ecology of the blue-tailed damselfly Ischnura elegans.
Front. Physiol.
Conference Abstract:
International Conference on Invertebrate Vision.
doi: 10.3389/conf.fphys.2013.25.00068
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Received:
22 Feb 2013;
Published Online:
09 Dec 2019.
*
Correspondence:
Dr. Miriam J Henze, Lund University, Department of Biology, Lund, 22362, Sweden, miriam.henze@biol.lu.se