Microscopic analysis of the microbiota of three commercial Phytoseiidae species (Acari: Mesostigmata)

Microbes associated with the external and internal anatomy of three commercially available predatory mite species, Phytoseiulus persimilis, Typhlodromips (=Amblyseius) swiskii, and Neoseiulus (=Amblyseius) cucumeris were examined using light microscopy, confocal laser scanning microscopy and fluorescence in-situ hybridization (FISH). Four microbe morphotypes were observed on external body regions. These included three microfungi-like organisms (named T1, T2 and T3) and rod-shaped bacteria (T4). Morphotypes showed unique distributions on the external body regions and certain microbes were found only on one host species. Microfungi-like T1 were present in all three species whereas T2 and T3 were present in only P. persimilis and T. swirskii respectively. T1 and T2 microbes were most abundant on the ventral structures of the idiosoma and legs, most frequently associated with coxae, coxal folds, ventrianal shields and epigynal shields. T3 microbes were most abundant on legs and dorsal idiosoma. T4 microbes were less abundant and were attached to epigynal shields of N. cucumeris and T. swirskii. Significant differences in distribution between seasons (spring and winter) suggest that there are fluctuations in the microbiota of phytoseiids in mass reared systems. FISH using the EUB338 (I-III) probes showed bacteria within the alimentary tract, in Malpighian tubules and anal atria. It is possible these have a role in absorbing excretory products or maintaining gut physiology. We suggest how microbes might be transmitted to offspring and throughout populations. The implications of these findings for commercial mass rearing are discussed. This study highlights the necessity of understanding the intrinsic microbiota of Phytoseiidae and other Acari