Ingestion of Varroa destructor by pseudoscorpions in honey bee hives confirmed by PCR analysis

Abstract

The pseudoscorpions, Nesochernes gracilis and Chelifer cancroides, appear to have potential for control of varroa mites (Varroa destructor), but have not been observed to predate on varroa in honey bee hives. A molecular method was developed to determine, without the need for observation, whether a candidate predator was eating varroa in commercial hives. DNA extracted from pseudoscorpions, which had been observed to have fed on varroa, and DNA from those that had not come in contact with varroa were amplified by polymerase chain reaction (PCR) with primers that target the cytochrome oxidase subunit 1 gene specific to V. destructor. Varroa DNA was detected up to four weeks after a known varroa feeding event from extractions of pseudoscorpion DNA. No varroa DNA could be detected in the pseudoscorpions not exposed to varroa mites. Varroa DNA was reliably extracted and identified from pseudoscorpions known to have preyed upon varroa, including C. cancroides confined within a varroa-infested commercial honey bee hive. This molecular technique can therefore be used as an indicator of varroa predation by chelifers without requiring visual observation of predation.Confirmació n por análisis de PCR de la ingestion de Varroa destructor por pseudoescorpiones en colmenas de abeja de la miel.Los pseudoescorpiones Nesochernes gracilis y Chelifer cancroides parecen tener el potencial de controlar los ácaros de varroa (Varroa destructor), pero no han sido observados depredando al ácaro en las colmenas de abeja melífera. Se ha desarrollado un método molecular para determinar, sin necesidad de observació n, si un depredador candidato ha estado comiendo varroa en las colmenas comerciales. Se extrajo ADN de pseudoescorpiones que habían sido observados alimentándose de varroa y de aquellos que no habían estado en contacto con varroa. Se amplificó mediante reacció n en cadena de la polimerasa (PCR) con cebadores del gen de la subunidad 1 de citocromo oxidasa específicos para V. destructor. El ADN de varroa se detectó en las extracciones del ADN de los escorpiones hasta 4 semanas después de que éstos se alimentaran del ácaro. No se detectó ADN de varroa en los pseudoescorpiones que no estuvieron expuestos a los ácaros. El ADN de varroa fue extraído e identificado correctamente de los pseudoescorpiones que habían depredado sobre varroa, incluyendo C. cancroides, que se encontró en una colmena comercial de abeja melífera infestada de varroa. Por tanto, esta técnica molecular puede utilizarse como un indicador de la depredació n sobre varroa por parte de quelíceros sin requerir la observació n visual de la depredació n.

Present and future perspectives of using biological control agents against pests of honey bees

“…Mass-rearing methods for two pseudoscorpions (Nesochernes gracilis and Heterochernes novaezealandiae) were developed in New Zealand, and N. gracilis showed the most promising role for biological control of Varroa (Read et al 2014). Also, a molecular technique based on detection of Varroa DNA in extractions of pseudoscorpion DNA was developed to confirm the predation in commercial hives without the need for observation (van Toor et al 2015). Rangel and Ward (2018) evaluated the ability of the predatory mite Stratiolaelaps scimitus (Mesostigmata: Laelapidae) to control Varroa under laboratory and field conditions.…”

A Pseudoscorpion's Promising Pinch: The venom of Chelifer cancroides contains a rich source of novel compounds

“…Especially the modulation of VdNav1 channels from V. destructor, an important pest of honeybee hives, may provide new insights on how C. cancroides efficiently control Varroa mites. C. cancroides has previously been considered to protect honey bees from mite infestations (van Toor et al, 2015).…”

Integrated Pest Management Control ofVarroa destructor(Acari: Varroidae), the Most Damaging Pest of (Apis melliferaL. (Hymenoptera: Apidae)) Colonies

“…They also considered the use of pseudoscorpions as a potentially viable option because they have been observed to feed on Varroa within A. cerana colonies ( Donovan and Paul 2006 ) and can be massed reared ( Read et al 2014 ). It was shown in a laboratory study that a single pseudoscorpion fed on as many as 1–9 Varroa per day ( Fagan et al 2012 ) and that the predation of Varroa by pseudoscorpions found in honey bee colonies was confirmed by molecular analysis ( van Toor et al 2015 ). However, feelings towards using pseudoscorpions to control Varroa are mixed as Thapa et al (2013) observed pseudoscorpions prefer to feed on dead A. cerana larvae and adults rather than Varroa .…”