Water mites (Acari: Hydrachnidiae) parasitic on aquatic hemipterans in Japan, with reference to host preferences and selection sites

Abstract

Water mites are known to temporarily live on the surface of aquatic insects in their life cycle. Investigations of the host–parasite relationship between water mites and aquatic insects are quite limited in Japan. Therefore, we examined several aquatic hemipterans to clarify the parasitic nature of water mites on aquatic insects. During the survey, the following seven hemipteran species were collected from farm ponds and rice fields in Kanagawa, Yamanashi, and Hyogo prefectures in 2011 and 2012: Appasus japonicus, Appasus major, Laccotrephes japonensis, Aquarius paludum, Ranatra chinensis, Kirkaldyia deyrolli, and Notonecta triguttata. Among these species, water mites were found only on Ap. japonicus and R. chinensis. The water mites were all in a post-larval resting stage and identified as Hydrachna spp. The mites attached to R. chinensis were clearly larger than those on Ap. japonicus. Although mites do not select by host sex and their abundance was not affected by the host body size, their abundance per female host was greater than per male host. Further, the mite parasitism on nymphs was greater than that on adults in Ap. japonicus. Concerning site selection on a host body of R. chinensis for attachment, mites significantly prefer the leg and meso- and metathoraxes to the abdomen, respiratory siphon, and head of a host insect. The results mentioned above accorded well with several studies in Europe.

Keywords:

• Hemiptera
• Hydrachnidiae
• Hydrachna
• parasitism
• water mites

Acknowledgements

We would like to thank K. Nakanishi for providing the Lethocerus indicus.