The highly specialized evolution of Strepsiptera has produced one of the most unusual eyes among mature insects, perhaps in line with their extremely complex and challenging life cycle. This relatively rare insect order is one of the few for which it has been unclear what spectral classes of photoreceptors any of its members may possess, an even more apt question given the nocturnal evolution of the group. To address this question, we performed electroretinograms on adult male Xenos peckii: we measured spectral responses to equi-quantal monochromatic light flashes of different wavelengths, and established VlogI relationships to calculate spectral sensitivities. Based on opsin template fits, we found maximal spectral sensitivity (λmax) in the green domain at 539 nm. Application of a green light to ‘bleach’ green receptors revealed that a UV peak was contributed to by an independent UV opsin with a λmax of 346 nm. Transcriptomics and a phylogenetic analysis including 50 other opsin sequences further confirmed the presence of these two opsin classes. While these findings do not necessarily indicate that these unorthodox insects have color vision, they raise the possibility that UV vision plays an important role in the ability of X. peckii males to find the very cryptic strepsipteran females that are situated within their wasp hosts.
The authors declare no competing or financial interests.
M.J. wrote portions of the manuscript and assisted in the data collection. S.P.N. collected the majority of the physiological data and A.S. worked on trancriptomics and bioinformatics. E.K.B. organized specimens, conceived and designed experiments, analyzed the physiology data and drafted and revised the manuscript.
This research was supported by the National Science Foundation under grants IOS1050754 and IOS1456757 to E.K.B.
Transcriptomic data were deposited in the NCBI Sequence Read Archive, and are available under SRP090411. Opsin sequences were submitted to NCBI GenBank and are available under the following accession numbers: BankIt1954825 long-wavelength, KX898496 and BankIt1954825 UV-wavelength, KX898497. ERG analysis software will be shared upon request.
Supplementary information available online at http://jeb.biologists.org/lookup/doi/10.1242/jeb.148361.supplemental
- Received August 16, 2016.
- Accepted September 29, 2016.
- © 2016. Published by The Company of Biologists Ltd