Experimental and Applied Acarology最新文献

The respiratory mite Orthohalarachne attenuata, a parasite inhabiting the respiratory tract of otariid and odobenid pinnipeds, faces unique biomechanical challenges in its marine environment. It must securely attach to the slippery mucosa of its host while maintaining the ability to traverse dry and wet surfaces to recruit new hosts. This study explores the morphology of the attachment structures and mechanisms of O. attenuata larvae using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), high-speed video analysis, and centrifugal force measurements. Our findings confirm that, as in most Mesostigmata, the larvae of O. attenuata possess a specialized pretarsal structure consisting of two highly sclerotized claws and a soft, resilin-rich arolium; however, our analyses reveal specific morphological and functional adaptations of this structure related to attachment in the walrus nasal mucosa. Attachment strategy varies with substrate: the claws hook into soft walrus mucosa, whereas the arolium inflates to adhere to smooth surfaces. This dynamic interaction suggests a complex mechanism involving muscle control, flexible cuticle structures, leg positioning, and hemolymph pressure. Larvae employ a tripod gait pattern, facilitating agile movement across diverse surfaces. Force measurements on various substrates (dry and wet hydrophilic glass, hydrophobic plastics, polishing paper of various roughness properties, and walrus mucosa) demonstrate the highest attachment forces on walrus mucosa (safety factor: 348.95 ± 38.70) and wet glass (safety factor: 167.80 ± 119.09), underscoring the critical role of both claws and arolium in securing adhesion. These findings highlight the strong evolutionary adaptations of O. attenuata to its challenging environment and offer valuable insights for the development of bioinspired attachment systems suited for soft and wet substrates, particularly in marine applications.

The control of cattle ticks (Rhipicephalus microplus) is critical in livestock farming, especially in pasture-based systems, as these ectoparasites are vectors of diseases such as bovine babesiosis and anaplasmosis. However, chemical pesticides have led to the development of resistance in tick populations, as well as in the elimination of beneficial soil fauna and the animal itself, making essential the development of alternative control methods. Essential oils (EOs), derived from plants, have emerged as a promising alternative due to their natural acaricidal and repellent properties. EOs rich in monoterpenes, carvacrol, and other bioactive compounds have demonstrated significant efficacy in controlling ticks, including those resistant to conventional pesticides. Plants such as cinnamon, cumin, and pepper have shown particular promise. The use of EOs not only offers a safer and more sustainable approach to tick management but also reduces the risks associated with chemical pesticide use. However, research on the use of essential oils in Mexico and the world is incipient. This opens a wide window of opportunity to generate alternative treatments for tick control. Therefore, further research is needed to optimize EO formulations and delivery methods for effective tick control in livestock systems.

The control of ticks is challenging owing to their ubiquity, complex ecologies, and difficulties relating to costs and non-target impacts of chemical control programs. Nature-based solutions centre around co-opting natural processes and biodiversity to address socio-environmental problems; and in some cases, rewilded species can provide nature-based solutions. In northern Japan, the winter ecology of ticks is poorly studied, though some species are believed to overwinter under the snow. Winter grazing activity of rewilded horses may disturb overwintering ticks, exposing them to sub-zero temperatures and killing them, thereby providing a nature-based solution to tick control. In this study we sought to ascertain: (i) whether ticks in Japan overwinter in leaflitter under the snow, (ii) whether the winter grazing activity of semi-rewilded horses is associated with reduced springtime tick abundance, (iii) whether semi-rewilded horses serve as key hosts for ticks during springtime. Paired leaflitter sampling undertaken at 10 sites during autumn and winter, respectively, showed that Haemaphysalis ticks overwinter in leaflitter under the snow. Using six paired 25 m² exclusion-grazing plots we tested whether winter horse grazing was associated with reduced springtime tick abundances but found no significant relationships. Springtime surveys revealed extremely low tick loads (0.2 ticks per horse) and prevalences (12%) on semi-rewilded horses. This suggests that while the winter grazing activities of horses may not appreciably reduce tick abundances, that horses likely do not serve as important amplifying hosts of ticks in northern Japan and that rewilded horses are neither a help nor hinderance to local tick control efforts in this region.

The cattle tick Rhipicephalus (Boophilus) microplus is a major ectoparasite of livestock, causing significant economic losses globally, with an estimated annual impact exceeding USD 3 billion in Brazil. Understanding the mechanisms of acaricide resistance is crucial to improve tick control strategies. This study investigated organophosphate (OP) resistance in ten R. microplus field strains from the Vale do Paraíba Region, São Paulo State, Brazil, through a combined approach integrating larval packet tests (LPT), biochemical enzyme inhibition assays, and sequencing of AChE1 and AChE2. Bioassays revealed high resistance levels to chlorpyrifos in most field strains. Biochemical tests using propoxur demonstrated significantly reduced acetylcholinesterase (AChE) inhibition in resistant strains, while sequencing identified 33 amino acid substitutions, including nine novel variants, distributed across AChE isoforms. The integration of phenotypic, biochemical, and genomic data shows that OP resistance in R. microplus from this region is primarily linked to target-site insensitivity, though the complexity of AChE polymorphism suggests multiple interacting mechanisms. These findings provide a comprehensive framework for resistance monitoring, reinforce the need for integrated control strategies, and highlight the importance of continued molecular surveillance to support sustainable tick management in Brazil.

Euseius amissibilis is a highly prevalent predator in citrus orchards. This study assessed the direct and residual toxicity of abamectin and bifenazate on adult male and female of E. amissibilis and its prey Tetranychus urticae. Additionally, we assessed the sublethal effects of abamectin on the biological and reproductive parameters of the predator. The results showed that both the predator and pest mite were more susceptible in the direct method than the residual method. The LC₅₀ values of bifenazate for T. urticae females were 4.13 and 5.89 mg active ingredient (a.i.)/L in the two methods, respectively. The LC₅₀ values for abamectin were found to be 0.064 and 0.074 mg a.i./L, respectively. The bioassay results demonstrated that bifenazate is safe for E. amissibilis, while abamectin was found to be toxic to the predatory mite; the lethal concentrations (LC₅₀) of abamectin for females were 4.51 mg a.i./L in the direct method and 24.78 mg a.i./L in the residual method. The comparative toxicity assays also confirmed the safety of bifenazate. The sublethal tests showed that abamectin negatively affected the oviposition period, fecundity, and longevity of E. amissibilis females. The findings indicate that bifenazate could be an effective choice for integrated management programs targeting T. urticae, especially when the primary natural enemy is E. amissibilis. Additionally, using abamectin may pose serious challenges for these programs.

Bioclimatic variables are ecologically sensitive indicators that help define the physiological tolerance limits of animals. Mites, being minute organisms, often face constraints due to their limited mobility, restricting them to narrow environmental ranges. Nonetheless, certain species, such as the red palm mite (RPM), Raoiella indica Hirst, exhibit efficient dispersal capacities. This phytophagous invasive mite commonly disperses via wind currents, especially during dry periods. However, abandoning the host plant carries risks, as individuals may become exposed to adverse environmental conditions. In this study, we examined how temperature and relative humidity, combined with different substrates-host plants (Cocos nucifera), non-host plants (Canavalia ensiformis), and inert material (plastic pots-Bio-Serv incorporation cells)-affect the survival of R. indica. Our findings were: (1) elevated temperatures and low humidity significantly decreased R. indica survival when away from the host plant; (2) under tropical-like conditions (27 °C and 75% RH), mites survived for an average of 3.5 days; and (3) in greenhouse settings, R. indica longevity was 53 days on the host plant, 1 day on the non-host plant, and 3 days on inert material. These results indicate that both climatic conditions and substrate type critically influence R. indica survival following dispersal events.

The pollination of wild plants and crops increasingly depends on insects, with the European honeybee (Apis mellifera) recognized as the most vital pollinator. A significant factor contributing to colony collapse disorder is the infestation of ectoparasitic varroa mites (Varroa destructor). As a result, there is considerable interest in developing new acaricides and optimizing doses to effectively manage these mites. This study aimed to evaluate the effects of low doses (0.125, 0.5, and 2 mM) of lithium salts (lithium acetate, lithium chloride, and lithium citrate) against varroa mites in honeybee colonies under field conditions. This study also assessed the effects of lithium salts on honeybee workers, particularly under conditions of food deprivation and low or high temperature stresses. Our findings indicated that colonies treated with 2 mM lithium chloride or 0.5 mM lithium citrate exhibited either 100% or 87.5% reduction of the initial mite infestation rates, respectively. Furthermore, the total mortality of bees in hives treated with lithium chloride did not differ significantly from those treated with oxalic acid. Additionally, the brood area of bee colonies receiving lithium salts was comparable to that of colonies treated with oxalic acid and fluvalinate, and significantly larger than that of untreated colonies. An in vitro study further demonstrated that honeybees receiving lithium salts displayed greater stress tolerance compared to those treated with fluvalinate under conditions of food deprivation, cold, and heat stress. This study demonstrated that low doses of lithium chloride and lithium citrate could effectively control varroa mite infestations in field conditions without significant negative impacts on bee brood development or stress tolerance.

When pests perceive the presence of natural enemies, their growth, development, and reproduction are significantly affected, a phenomenon known as non-consumptive effects (NCEs) of predators. Understanding the impact of NCEs on pests can help optimize biological control strategies. Neoseiulus bicaudus (Wainstein) is an effective predator of Tetranychus turkestani (Ugarov & Nikolskii), but its NCEs on this pest remain unclear, as does whether host plants influence the predation-induced stress. This study employed two-sex life table analysis to investigate how long-term NCEs affect the life-history traits and population dynamics of T. turkestani on common bean (Phaseolus vulgaris) and soybean (Glycine max). Results showed that the NCEs of N. bicaudus on T. turkestani varied between the two host plants. On both hosts, the developmental duration of the protonymph stage significantly shortened, while fecundity was unaffected by NCEs. NCEs significantly reduced the lifespan of T. turkestani on common bean but had no significant effect on lifespan on soybean. On common bean, the mean generation time decreased from 15.99 to 14.68 days under NCE, with no significant changes in intrinsic rate of increase or net reproductive rate. In contrast, on soybean, NCEs significantly increased the intrinsic rate of increase by 1.38-fold and the net reproductive rate by 1.43-fold, while shortening the mean generation time by 3.15 days. This study indicates that T. turkestani experiences negative NCEs on common bean but positive effects on soybean. Therefore, host plant characteristics should be comprehensively considered when evaluating the impacts of NCEs in biological control programs.

The parasite-host relationships of Amblyomma cajennense sensu stricto, one of the species of the Amblyomma cajennense complex that occurs in the state of Maranhão, are poorly known and are restricted to its association with horses and humans. This study evaluated, for the first time, the effect of hosts on the oviposition of A. cajennense engorged females, naturally collected from wild animals and humans, as well as those experimentally fed on cattle and highlights the importance of the relationship between A. cajennense and different hosts in maintaining tick populations in the Amazon biome. Females fed on horses and capybaras exhibited the highest egg production efficiency (> 90%) and high hatching rates (≥ 95%), whereas, females collected from zebras and zebroids showed lowest egg production efficiency (~ 70%). The experimental infestation on cattle resulted in low hatching rates and low reproductive efficiency. The record of parasitism in zebras, zebroids, and wildebeests is unprecedented. Additionally, the finding of a female feeding in a human in the present study is a matter of concern and needs to be further investigated because of a potential candidate of this tick in the transmission of the Rickettsia amblyommatis, an agent of uncertain pathogenicity.

Physiological and behavioral responses of prey to predation risks, the non-consumptive effects, have ecological impacts that can be as great as or even greater than direct predation. In nature, the ovipositing females in a large population may be continuously exposed to olfactory cues from the dead conspecifics of different developmental stages, even in the absence of predators. In this study, we investigated how odour cues from killed conspecifics of different developmental stages affect survival, fecundity, offspring development, and population growth of the spider mite Tetranychus ludeni Zacher (Acari: Tetranychidae), an invasive agricultural and horticultural pest, by continuously exposing the mated females to olfactory cues from killed eggs, female deutonymphs, or female adults. Results show that females exposed to these cues shortened longevity by 21-31% and reduced fecundity by 25-51% compared to control, with the strongest effects from killed eggs. Daughter production declined by up to 80%, leading to significant reductions in net reproductive rate (R₀) and intrinsic rate of increase (rₘ) of T. ludeni. Females perceiving killed adult-borne cues peaked their reproduction early, exhibiting a terminal investment strategy; while those detecting killed egg-borne cues displayed a flattened reproductive trajectory with a delay of egg hatching. These responses of T. ludeni females demonstrate that killed conspecific-borne cues elicited stage-specific effects, with killed eggs signalling the greatest ecological threat to the ovipositing females. Our results highlight that T. ludeni could integrate conspecific chemical information into reproductive decisions under risk environments. This study delivers insights into the mechanisms of non-consumptive stress mediated-regulation in suppressing prey population growth, suggesting that non-consumptive effects induced by killed conspecifics may amplify the impacts of predators on spider mite population dynamics.