Wolbachia in a Predator–Prey System: 16S Ribosomal Dna Analysis of Two Phytoseiids (Acari: Phytoseiidae) and Their Prey (Acari: Tetranychidae)

Abstract

Using specific polymerase chain reaction (PCR) primers, the 5' region of Wolbachia 16S ribosomal DNA from the predatory mite Metaseiulus occidentalis (Nesbitt) and the twospotted spider mite, Tetranychus urticae Koch, was amplified. Because the prey contains Wolbachia , a method to eliminate amplification of transient Wolbachia from the gut contents was necessary. We found that if the otherwise uninfected phytoseiid Amblyseius reductus Wainstein was fed spider mite prey containing Wolbachia , a positive PCR signal was detectable immediately after feeding, but not 4 h later. M. occidentalis remained positive for Wolbachia by the PCR even 48 h after feeding, although a stronger signal was present at 24 h or less. Wolbachia DNA could be amplified from the predator's eggs, suggesting it is transovarially transmitted and a stable symbiont in this predatory mite. All but 1 of the laboratory colonies of M. occidentalis tested were positive for Wolbachia by the PCR, including those from other laboratories. One fresh collection of M. occidentalis and their prey Panonychus ulmi (Koch) were tested immediately and again 5 d after collection from the field, but a positive PCR signal was never detected. A field-collected sample of T. urticae did not test positive for Wolbachia , although a Wolbachia -specific signal was detected in a population of the strawberry spider mite, T. turkestani Ugarov & Nikolski, collected simultaneously from the same field. PCR products from 1 adult female of the Russian Select strain of M. occidentalis , 60 eggs of the COS strain of M. occidentalis , and 1 male T. urticae were directly sequenced. Phylogenetic analyses placed them within the same clade as Wolbachia from insects, clustered together with the type species, Wolbachia pipientis Hertig, from Culex pipiens L. The Wolbachia from these mites was not similar to Wolbachia persica Suiter & Weiss from another acarine, the fowl tick, Argas persicus (Oken). The sequence similarity between the mite and insect Wolbachia provides more evidence for the horizontal transfer of this microorganism between diverse arthropods.