Abstract
Microbes associated with the external and internal anatomy of three commercially available predatory mite species—Phytoseiulus persimilis, Typhlodromips (= Amblyseius) swirskii, 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 batches suggest temporal fluctuations in the microbiota of phytoseiids in mass-reared systems. FISH showed bacteria within the alimentary tract, in Malpighian tubules and anal atria. These may aid absorption of excretory products or maintaining gut physiology. We suggest a mechanism by which microbes may be transmitted to offspring and throughout populations. This study aims to improve our knowledge of this poorly understood area and highlights the necessity of understanding the microbiota of Acari.
Highlights
The mite family Phytoseiidae (Acari: Mesostigmata) contains 2789 described species (Demite et al 2014)
T. swirskii and N. cucumeris have been used to effectively spread fungal spores of Beauveria bassiana to improve the biological control of Diaphorina citri, the citrus psyllid (Zhang et al 2015)
Microbes present on the integument of the mites were primarily divided into four morphotypes by describing shape, size, dye affinity or other characteristics; these are all represented in Fig. 1, which summarises the various types
Summary
The mite family Phytoseiidae (Acari: Mesostigmata) contains 2789 described species (Demite et al 2014). They are generally found on aerial parts of plants and sometimes in soil. T. swirskii and N. cucumeris have been used to effectively spread fungal spores of Beauveria bassiana to improve the biological control of Diaphorina citri, the citrus psyllid (Zhang et al 2015). Despite their importance as biological control agents, little is known of the intrinsic Phytoseiidae microbiota or how their morphology interacts with microbes within the environment or intrinsic microbiota. Microbes with pathogenic effects have been relatively well described (Bjørnson et al 2000; van der Geest et al 2000; Pukall et al 2006; Bjørnson 2008; Schütte et al 2008; Bruin and van der Geest 2009); little is known about other microbial partners regularly associated with asymptomatic phytoseiids
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