Ectoparasitism of anisopteran dragonflies (Insecta: Odonata) by water mite larvae of Arrenurus spp. (Arachnida: Hydrachnida: Arrenuridae) in Central India

Abstract

There is no report on the frequency, species selection and site specificity of water mites’ ectoparasitism within and among dragonfly species of India. Here, we present a field survey of the species selection and site specificity of ectoparasite larval arrenurid mites on anisopteran adults at Nagpur city of central India. Since the female odonates returns to water to oviposit, it would be of some advantage for the mite to show a female-biased parasitism in order to return to water easily and continue the remaining aquatic part of their life cycle. A total of 204 specimens of anisopteran odonates belonging to 11 species were examined for the presence of larval Arrenurus spp. as ectoparasites during the post-monsoon (August – September 2010) and summer (March – April 2011) months from a large pond in central India. Only 14 dragonflies specimens of six species (Acisoma panorpoides, Brachythemis contaminata, Crocothemis servilia, Diplacodes trivialis, Neurothemis t. tullia, and Trithemis pallidinervis) were found to be parasitized (overall prevalence of 6.86%). The prevalence for C. servilia was 28.6%, followed by Trithemis pallidinervis and Acisoma panorpoides at 21.4%. The total number of parasites recorded was 465 at an average of 33.26 perspecimen. The parasite load per host species was the highest in T. pallidinervis (92.6) followed by C. servilia (24). In C. servilia, A. panorpoides and D. trivialis the mites were attached venterally to the thorax and were mostly arranged in a ‘v’ or triangular shape, while in B. contaminata and T. pallidinervis the mites were found all over the ventral abdomen. In one T. pallidinervis male and o e C. servilia female, mites were found both on the thorax as well as the abdomen. The maximum number of mites found on an individual dragonfly was on the female abdomen of T. pallidinervis (114), while only one mite was found on the thorax of a male C. servilia. Mite infestation was sex-biased – 71.0% and 85.7% of infested odonates were females in August–September and March – April, respectively.