Spider venom peptides Ht1a and Gg1a are toxic to honeybee parasite Varroa destructor by topical application

Abstract Global food supply strongly depends on honeybee pollination services, which are threatened by insecticides and pests such as parasitic Varroa destructor mites. Chemical varroacides/acaricides are hampered by resistance development, necessitating the development of sustainable and environmentally friendly alternatives, with arthropod venom peptides being considered promising sources of acaricidal toxins. With only a few acaricidal venom peptides being reported, we performed a systematic topical screening of 50 arthropod venoms against V. destructor , with 78% of the venoms causing 100% mortality after 24 h. Deconvolution of the venoms from the Tasmanian cave spider Hickmania troglodytes and the Giant Japanese funnel-web spider Gigathele gigas led to identification of the varroacidal peptides Ht1a and Gg1a. Topical application of Ht1a and Gg1a reduced varroa mite but not honeybee survival, despite Ht1a inhibiting voltage-gated sodium channels from varroa and honeybee with equal potency. Ht1a and Gg1a were inactive against human skeletal muscle (hNa V 1.4), cardiac (Na V 1.5), neuronal Na V channel isoforms, and human voltage-gated calcium channel Ca V 2.2. At human α3β2/4 nicotinic acetylcholine receptors, Gg1a was inactive while 10 µM of Ht1a partially blocked nicotine-mediated Ca 2+ influx. Our data reveal Ht1a and Gg1a as promising candidates for the development of novel varroa mite treatments of honeybee hives.