A very rare case of intersexuality in water mites of the genus Arrenurus Duges, 1834 (Acari, Hydrachnidia)

In recent years, many authors have drawn attention to the fact that substances of anthropogenic origin introduced to the environment can disrupt the normal functioning of the endocrine system in animals, a phenomenon known as endocrine disruption. These substances are called endocrine-disrupting chemicals. It has been suggested that many cases of adverse changes in health (including the phenomenon of intersexuality) in a range of wildlife species are owing to exposure to endocrine disrupters. The main objective of this study was to report intersexuality in water mites of the genus Arrenurus. The intersex specimens of Arrenurus crassicaudatus Kramer, 1875 were more similar in their overall appearance to males than to females, but their external genital organ was more like the genital organ of a female than that of a male. Based on their morphological features and body measurements, intersex A. crassicaudatus individuals should be described as feminized males. The causes of intersexuality in aquatic invertebrates are still unclear and several mechanisms may be involved: parasitism, pollution affecting parasite function, and pollution directly causing the intersexuality seem to be the main factors increasing the frequency of the phenomenon.