Acarine attractants: Chemoreception, bioassay, chemistry and control

Abstract

The Acari are of significant economic importance in crop production and human and animal health. Acaricides are essential for the control of these pests, but at the same time, the number of available pesticides is limited, especially for applications in animal production. The Acari consist of two major groups, the mites that demonstrate a wide variety of life strategies, i.e., herbivory, predation and ectoparasitism, and ticks which have evolved obligatory hematophagy. The major sites of chemoreception in the acarines are the chelicerae, palps and tarsi on the forelegs. A unifying name, the “foretarsal sensory organ” (FSO), is proposed for the first time in this review for the sensory site on the forelegs of all acarines. The FSO has multiple sensory functions including olfaction, gustation, and heat detection. Preliminary transcriptomic data in ticks suggest that chemoreception in the FSO is achieved by a different mechanism from insects. There are a variety of laboratory and field bioassay methods that have been developed for the identification and characterization of attractants but minimal techniques for electrophysiology studies. Over the past three to four decades, significant progress has been made in the chemistry and analysis of function for acarine attractants in mites and ticks. In mites, attractants include aggregation, immature female, female sex and alarm pheromones; in ticks, the attraction–aggregation–attachment, assembly and sex pheromones; in mites and ticks host kairomones and plant allomones; and in mites, fungal allomones. There are still large gaps in our knowledge of chemical communication in the acarines compared to insects, especially relative to acarine pheromones, and more so for mites than ticks. However, the use of lure-and-kill and lure-enhanced biocontrol strategies has been investigated for tick and mite control, respectively, with significant environmental advantages which warrant further study.

Chemosensing of honeybee parasite, Varroa destructor: Transcriptomic analysis

“…As the most successful group on earth, Arthropods possess remarkable chemosensory abilities. Their olfactory neurons are encased in sensory hairs, mostly located on an appendage such as the antenna in insects 1 or the forelegs in Acarids 2 . The sensory hairs are hollow perforated structures, into which the dendrite(s) of the olfactory neurons project within the sensillar lymph.…”

Varroa chemosensory proteins: some are conserved across Arthropoda but others are arachnid specific

“…Regarding membrane-bound proteins and receptors, all of the potential chemoreceptors found in Chelicerata to date belong to the ion-gated channel receptor groups with the exception of potential G-protein coupled receptors (GPCRs) found in the forelegs of the dog tick Dermacentor variabilis (Carr and Roe, 2016), resembling odorant receptors (ORs) identified to date only in insects. The identified chemoreceptor homologues in Chelicerata include members of potential olfactory ionotropic receptors (IRs), gustatory receptors (GRs) (Eyun et al, 2017) and the more divergent degenerin/epithelial Na+ channel (ENaC) family as well as the transient receptor potential (TRP) family (Ngoc et al, 2016).…”

Proteomic analysis of chemosensory organs in the honey bee parasite Varroa destructor: a comprehensive examination of the potential carriers for semiochemicals

“…Compared to insects, chemical communication in other arthropods, particularly Chelicerata, is poorly understood. Most of the studies are focused on morphology 11 and electrophysiology [12][13][14] while several papers report on the identification of putative semiochemicals 8,9,[15][16][17][18] .…”