Abstract
The decomposition of vertebrate carcasses is an important ecosystem function. Soft tissues of dead vertebrates are rapidly decomposed by diverse animals. However, decomposition of hard tissues such as hairs and feathers is much slower because only a few animals can digest keratin, a protein that is concentrated in hairs and feathers. Although beetles of the family Trogidae are considered keratin feeders, their ecological function has rarely been explored. Here, we investigated the keratin-decomposition function of trogid beetles in heron-breeding colonies where keratin was frequently supplied as feathers. Three trogid species were collected from the colonies and observed feeding on heron feathers under laboratory conditions. We also measured the nitrogen (δ15N) and carbon (δ13C) stable isotope ratios of two trogid species that were maintained on a constant diet (feathers from one heron individual) during 70 days under laboratory conditions. We compared the isotopic signatures of the trogids with the feathers to investigate isotopic shifts from the feathers to the consumers for δ15N and δ13C. We used mixing models (MixSIR and SIAR) to estimate the main diets of individual field-collected trogid beetles. The analysis indicated that heron feathers were more important as food for trogid beetles than were soft tissues under field conditions. Together, the feeding experiment and stable isotope analysis provided strong evidence of keratin decomposition by trogid beetles.
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Acknowledgments
We thank M. Mashiko, Y. Toquenaga, K. Kawakami and T. Amano for providing valuable information about the study sites and herons. K. Kawakami also provided us with some heron feathers. We also thank R. Nakashita, K. Fukumori, F. Hyodo and H. Doi for advice on our stable isotope analyses. We thank three anonymous reviewers for helpful comments on our manuscript. This research was partly supported by a Grant-in-Aid for Scientific Research (no. 25292034) and the Forestry and Forest products Research Institute. The experiments complied with the laws of Japan.
Author contributions
SS and HI conceived and designed the experiments. SS performed field collections and feeding experiments. HI performed stable isotope analyses. SS and HI analysed the data. SS wrote the manuscript.
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The authors declare there are no competing financial interests.
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Communicated by: Sven Thatje
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Sugiura, S., Ikeda, H. Keratin decomposition by trogid beetles: evidence from a feeding experiment and stable isotope analysis. Naturwissenschaften 101, 187–196 (2014). https://doi.org/10.1007/s00114-013-1137-z
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DOI: https://doi.org/10.1007/s00114-013-1137-z