Cold hardiness and biochemical response to low temperature of the unfed bush tick Haemaphysalis longicornis (Acari: Ixodidae)

Abstract

BackgroundThe survival of overwintering ticks, is critical for their subsequent population dynamics in the spring, and consequent transmission of tick-borne diseases. Survival is largely influenced by the severity of the winter temperatures and their degree of cold hardiness at the overwintering stage. The bush tick Haemaphysalis longicornis, is widely distributed in China, and can transmit various pathogens that pose serious medical/veterinary problems. In the present study we investigated the effect of low temperature stress to tick survival, super-cooling point and body content of water, glycerol and total protein.MethodsAfter various temperature acclimations, the super-cooling point was measured by Ni/CrNi-thermocouples with a precision temperature recorder. Water content was determined from weight loss of the sample exposed to 60°C for 48 h. Glycerol content was determined using Free Glycerol Reagent as directed by the manufacturer, and total protein was determined using the Bradford assay.ResultsThe 50% mortality temperatures for the adults and nymphs were -13.7°C and -15.2°C, respectively; and the discriminating temperatures for the adults and nymphs were -16.0°C and -17.0°C, respectively. The super-cooling points of the adults and nymphs were -19.0°C and -22.7°C, respectively. The water content of adult H. longicornis decreased substantially after acclimation at 0°C for 10 d, whereas the nymphs decreased after acclimation at 0°C for 20 d, and the glycerol and proteins of both nymphs and adults were significantly increased (p < 0.01) when stressed at 0°C for 10 d.ConclusionsIn H. longicornis, low temperature stress can enhance its cold hardiness and trigger appropriate responses, including reducing water content, and increasing glycerol and total protein content.

Preliminary prediction of the potential distribution and consequences of Haemaphysalis longicornis using a simple rule-based climate envelope model

“…Third, this tick has a large distribution, including northern China and the Russian territories of Primorsky Krai, where it was documented to be able to overwinter despite cold temperatures and snow cover (Zheng et al, 2011). Prior literature indicates that while it is susceptible to freezing temperatures, this tick is able to acclimate to cold temperatures, increasing their glycerol and protein content (Yu et al, 2014). Finally, given that we have documented evidence that Haemaphysalis longicornis can overwinter in the counties where it was detected on the Atlantic coast, where we know there is frost and snow cover above these environmental criteria, it would seem counterintuitive to include these in our adopted rule-based climate envelope model.…”

“…Prior literature indicates that while it is susceptible to freezing temperatures, this tick is able to acclimatmean either air or ground frost at various levels. Third, Lawrence et al (2017) has shown in their sensitive to cold temperatures, increasing their glycerol and protein content (Yu et al, 2014). Finally, given that we have documented evidence that Haemaphysalis longicornis can overwinter in the counties where it was detected on the Atlantic coast, where we know there is frost and snow cover above these environmental criteria, it would seem counterintuitive to include these in our adopted rulebased climate envelope model.…”

Larval thermal characteristics of multiple ixodid ticks underlie their range dynamics

“…Preferential temperature ranges of ticks was between 15°C and 25°C with the exception of D. variabilis , which displayed a higher proportion of ticks at 12°C. The lowered temperature preference in D. variabilis could be a higher tolerance to colder temperatures (Rosendale et al, 2016b; Yu et al, 2014) or an impaired ability to detect temperatures. Importantly, is unlikely that D. variabilis was immobilized by the lower temperature since activity was noted as low as 10°C.…”

Predicting the potential distribution of Amblyomma americanum (Acari: Ixodidae) infestation in New Zealand, using maximum entropy-based ecological niche modelling

“…Spontaneous freezing and direct chilling were not considered significant mortality factors in the field but inoculative freezing: ice nucleation around organic or inorganic entities (Costanzo and Lee 2013) is an important cause of overwintering mortality, following 2 h at − 5 and − 3 °C in direct contact with ice (Burks et al 1996). Haemaphysalis longicornis is freeze susceptible (Yu et al 2014) and gradual exposure to low temperatures can enhance its cold hardiness, while the possible formation of cryoprotective proteins is suggested, but not proven. Stewart et al (1998) found that adults of A. americanum did not undergo behavioural diapause when winter-exposed.…”