Feeding by Tropilaelaps mercedesae on pre- and post-capped brood increases damage to Apis mellifera colonies

Abstract

Tropilaelaps mercedesae parasitism can cause Apis mellifera colony mortality in Asia. Here, we report for the first time that tropilaelaps mites feed on both pre- and post-capped stages of honey bees. Feeding on pre-capped brood may extend their survival outside capped brood cells, especially in areas where brood production is year-round. In this study, we examined the types of injury inflicted by tropilaelaps mites on different stages of honey bees, the survival of adult honey bees, and level of honey bee viruses in 4th instar larvae and prepupae. The injuries inflicted on different developing honey bee stages were visualised by staining with trypan blue. Among pre-capped stages, 4th instar larvae sustained the highest number of wounds (4.6 ± 0.5/larva) while 2nd-3rd larval instars had at least two wounds. Consequently, wounds were evident on uninfested capped brood (5th-6th instar larvae = 3.91 ± 0.64 wounds; prepupae = 5.25 ± 0.73 wounds). Tropilaelaps mite infestations resulted in 3.4- and 6-fold increases in the number of wounds in 5th-6th instar larvae and prepupae as compared to uninfested capped brood, respectively. When wound-inflicted prepupae metamorphosed to white-eyed pupae, all wound scars disappeared with the exuviae. This healing of wounds contributed to the reduction of the number of wounds (≤10) observed on the different pupal stages. Transmission of mite-borne virus such as Deformed Wing Virus (DWV) was also enhanced by mites feeding on early larval stages. DWV and Black Queen Cell Virus (BQCV) were detected in all 4th instar larvae and prepupae analysed. However, viral levels were more pronounced in scarred 4th instar larvae and infested prepupae. The remarkably high numbers of wounds and viral load on scarred or infested developing honey bees may have caused significant weight loss and extensive injuries observed on the abdomen, wings, legs, proboscis and antennae of adult honey bees. Together, the survival of infested honey bees was significantly compromised. This study demonstrates the ability of tropilaelaps mites to inflict profound damage on A. mellifera hosts. Effective management approaches need to be developed to mitigate tropilaelaps mite problems.

Diversity and Global Distribution of Viruses of the Western Honey Bee, Apis mellifera

“…The mechanisms of dispersal of viruses of honey bees could be investigated by studying the prevalence and biogeography of newly described viruses that do not yet occur globally. The spread of invasive species such as Vespa velutina and Apis florea [113,168] and vectors such as V. destructor and T. mercedesae is also alarming, as these species are known to be infected by viruses of A. mellifera [138,172,173].…”

Individual-Level Comparisons of Honey Bee (Hymenoptera: Apoidea) Hygienic Behavior Towards Brood Infested with Varroa destructor (Parasitiformes: Varroidae) or Tropilaelaps mercedesae (Mesostigmata: Laelapidae)

“…In Europe, North and Central America, and most of temperate Asia, Varroa destructor (Anderson and Trueman) is by far the mite species with the greatest economic impact. In those parts of Asia in which the introduced A. mellifera coexists with autochthonous giant honey bees (Apis dorsata, Apis breviligula, and/or Apis laboriosa), mites of the genus Tropilaelaps are often equally or even more damaging to the A. mellifera beekeeping industry [5,6].…”

“…Two species, Tropilaelaps clareae and Tropilaelaps mercedesae , are known to cause damage also to A. mellifera colonies, and at least T. mercedesae (Anderson and Morgan) is capable of transmitting Deformed Wing Virus as well as black queen cell virus [ 7 , 8 ]. Unlike V. destructor , adults of T. mercedesae also feed on early larval stages of A. mellifera [ 6 ]. It is not clear, however, whether mites of the genus Tropilaelaps are able to feed on adult bees, and they survive for only a few days if the host colony is broodless [ 5 ].…”

“…An important question now is whether the removal of T. mercedesae- and V. destructor -infested brood really constitutes the same trait. Given that the type of injuries produced by feeding of T. mercedesae on larvae and pupae is distinct from that produced by V. destructor [ 6 , 26 ], it may be hypothesized that different genetic specializations are required on behalf of the hygienic workers in order to sense them across the cell capping. Also, the role of hygienic behavior in A. cerana resistance to T. mercedesae remains to be elucidated.…”

Tropilaelaps mercedesae parasitism changes behavior and gene expression in honey bee workers

“…Although study design, data collection and analysis, decision to publish, or preparation of the manuscript. lacking a phoretic phase involving honey bee adults, the adverse effects of Tropilaelaps infestation during the precapping stages may last to the adult stage, with remarkably higher numbers of wounds and virus infection rates observed in infested adult honey bees [17]. Infestation of T. mercedesae lead to a reduction in weight and longevity, and increase of the sugar syrup and pollen consumption in adult worker bees [4,18].…”