Development and Reproductive Capacity of the Miyake Spider Mite Eotetranychus kankitus (Acari: Tetranychidae) at Different Temperatures

Eotetranychus kankitus (Acari: Tetranychidae) is an important pest of citrus. Assessing life history parameters is crucial to developing an ecologically sound pest management program. Of the many factors that affect life history parameters of herbivorous insects and mites, temperature has the greatest influence on development rate and reproductive potential. We investigated the effects of temperatures from 15 to 40 °C on the demographic parameters of E. kankitus under a long-day (16:8 (L:D) h) photoperiod. The egg-to-adult development time of E. kankitus decreased as the temperature increased from 15 to 32.5 °C. At 35 °C, the female laid eggs that died at the larval stage. The estimated lower thermal thresholds (t₀) were 11.01 and 10.48 °C, and the thermal constants (K) were 190.67 and 188.63 degree-days for egg-to-adult females and egg-to-adult males, respectively. The intrinsic optimal temperatures (T_Ø) for development were 21.79 and 21.74 °C, respectively. The bootstrap-match technique was used in the construction of the life table paramaters. The net reproductive rate (R₀) decreased as temperature increased from 20 to 30 °C, but the lowest rate was observed at 15 °C. The intrinsic rate of natural increase (r) increased from 0.0299 day^-1 at 15 °C to 0.1822 day^-1 at 30 °C. These findings provide a critical theoretical basis for predicting the occurrence of E. kankitus populations under climate warming and for developing appropriate control strategies.

Emergent properties in the responses of tropical corals to recurrent climate extremes

The frequency, intensity, and spatial scale of climate extremes are changing rapidly due to anthropogenic global warming.^1,2 A growing research challenge is to understand how multiple climate-driven disturbances interact with each other over multi-decadal time frames, generating combined effects that cannot be predicted from single events alone.^3-5 Here we examine the emergent dynamics of five coral bleaching events along the 2,300 km length of the Great Barrier Reef that affected >98% of the Reef between 1998 and 2020. We show that the bleaching responses of corals to a given level of heat exposure differed in each event and were strongly influenced by contingency and the spatial overlap and strength of interactions between events. Naive regions that escaped bleaching for a decade or longer were the most susceptible to bouts of heat exposure. Conversely, when pairs of successive bleaching episodes were close together (1-3 years apart), the thermal threshold for severe bleaching increased because the earlier event hardened regions of the Great Barrier Reef to further impacts. In the near future, the biological responses to recurrent bleaching events may become stronger as the cumulative geographic footprint expands further, potentially impairing the stock-recruitment relationships among lightly and severely bleached reefs with diverse recent histories. Understanding the emergent properties and collective dynamics of recurrent disturbances will be critical for predicting spatial refuges and cumulative ecological responses, and for managing the longer-term impacts of anthropogenic climate change on ecosystems.

Summer and Winter Marine Heatwaves Favor an Invasive Over Native Seaweeds

Marine heatwaves (MHWs) are emerging as forceful agents of ecosystem change and are increasing in frequency, duration, and intensity with climate change. During MHWs, physiological thresholds of native species may be exceeded while the performance of invasive species with warm affinities may be enhanced. As a consequence, MHWs could significantly alter an ecosystem's invasive dynamics, but such interactions are poorly understood. Following a 10-d acclimation period, we investigated the physiological resistance and resilience of an intertidal rock pool assemblage invaded by the seaweed Sargassum muticum to realistic 14-d marine heatwave scenarios (+1.5°C, +2.0°C, +3.5°C) followed by a 14-d recovery period. We conducted mesocosm experiments in both summer and winter to investigate temporal variability of MHWs. MHW treatments had clear negative impacts on native seaweeds (Fucus serratus and Chondrus crispus) while enhancing the performance of S. muticum. This pattern was consistent across season indicating that acclimation to cooler ambient temperatures results in winter MHWs having significant impacts on native species. As climate warming advances, this may ultimately lead to changes in competitive interactions and potentially exclusion of native species, while invasive species may proliferate and become more conspicuous within temperate rocky shore environments.

Summer and Winter Marine Heatwaves Favor an Invasive Over Native Seaweeds

Marine heatwaves (MHWs) are emerging as forceful agents of ecosystem change and are increasing in frequency, duration, and intensity with climate change. During MHWs, physiological thresholds of native species may be exceeded while the performance of invasive species with warm affinities may be enhanced. As a consequence, MHWs could significantly alter an ecosystem's invasive dynamics, but such interactions are poorly understood. Following a 10-d acclimation period, we investigated the physiological resistance and resilience of an intertidal rock pool assemblage invaded by the seaweed Sargassum muticum to realistic 14-d marine heatwave scenarios (+1.5°C, +2.0°C, +3.5°C) followed by a 14-d recovery period. We conducted mesocosm experiments in both summer and winter to investigate temporal variability of MHWs. MHW treatments had clear negative impacts on native seaweeds (Fucus serratus and Chondrus crispus) while enhancing the performance of S. muticum. This pattern was consistent across season indicating that acclimation to cooler ambient temperatures results in winter MHWs having significant impacts on native species. As climate warming advances, this may ultimately lead to changes in competitive interactions and potentially exclusion of native species, while invasive species may proliferate and become more conspicuous within temperate rocky shore environments.

Thermal thresholds heighten sensitivity of West Nile virus transmission to changing temperatures in coastal California

Temperature is widely known to influence the spatio-temporal dynamics of vector-borne disease transmission, particularly as temperatures vary across critical thermal thresholds. When temperature conditions exhibit such 'transcritical variation', abrupt spatial or temporal discontinuities may result, generating sharp geographical or seasonal boundaries in transmission. Here, we develop a spatio-temporal machine learning algorithm to examine the implications of transcritical variation for West Nile virus (WNV) transmission in the Los Angeles metropolitan area (LA). Analysing a large vector and WNV surveillance dataset spanning 2006-2016, we found that mean temperatures in the previous month strongly predicted the probability of WNV presence in pools of Culex quinquefasciatus mosquitoes, forming distinctive inhibitory (10.0-21.0°C) and favourable (22.7-30.2°C) mean temperature ranges that bound a narrow 1.7°C transitional zone (21-22.7°C). Temperatures during the most intense months of WNV transmission (August/September) were more strongly associated with infection probability in Cx. quinquefasciatus pools in coastal LA, where temperature variation more frequently traversed the narrow transitional temperature range compared to warmer inland locations. This contributed to a pronounced expansion in the geographical distribution of human cases near the coast during warmer-than-average periods. Our findings suggest that transcritical variation may influence the sensitivity of transmission to climate warming, and that especially vulnerable locations may occur where present climatic fluctuations traverse critical temperature thresholds.

The Effect of Granisetron on Sensory Detection and Pain Thresholds in Facial Skin of Healthy Young Males

Background: The specific serotonin type 3 (5-HT₃)-receptor antagonist granisetron effectively reduces clinical as well as experimental muscle pain and hyperalgesia and with a duration that exceeds that of lidocaine. Hence, it may be an alternative to lidocaine as a local anesthetic. There are also some indications that granisetron in addition to 5-HT₃ receptors blocks sodium channels. Thus, the local anesthetic effect by granisetron may resemble that of lidocaine, but this has not been tested. The aim of this study was therefore to compare the effect granisetron has on facial skin sensitivity to the effect of lidocaine and isotonic saline.

Methods: This was a randomized, controlled, and double-blind study, in which 1 ml of either granisetron (test-substance), lidocaine (positive control), or isotonic saline (negative control) was injected into the skin over the masseter muscle at three different occasions in 18 healthy males (27.2 ± 5.8 years old). Skin detection thresholds and pain thresholds for thermal stimuli as well as mechanical detection thresholds and sensitivity to a painful mechanical (pinprick) stimulus were assessed before (baseline) and 5, 20, 40, and 60 min after injection. The quality and area of subjective sensory change over the cheek were assessed 20 min after injection.

Results: All substances increased the mechanical detection threshold (granisetron: p = 0.011; lidocaine: p = 0.016; saline: p = 0.031). Both granisetron and lidocaine, but not isotonic saline, increased the heat detection thresholds (p < 0.001 and p < 0.02, respectively), but not the cold detection thresholds. Granisetron and lidocaine also reduced pinprick pain (p = 0.001 for each comparison). There were no significant differences between granisetron and lidocaine for any of these variables. There was no effect on thermal pain thresholds for any substance.

Conclusion: The similar analgesic patterns on mechanical sensory and pain thresholds as well as thermal sensory thresholds over the facial skin by subcutaneous injection of granisetron and lidocaine shown in this study and the absence of paresthesia, in combination with the reduced pain intensity and pressure pain sensitivity shown in previous studies, indicate that granisetron might be a novel candidate as a local anesthetic.

The Effects of Constant and Fluctuating Temperatures on Development of Diaphorina citri (Hemiptera: Liviidae), the Asian Citrus Psyllid

The effects of six average daily temperatures, 15, 20, 25, 30, 32, and 35°C, that were either constant or fluctuating over 24 h on development times of California-sourced Diaphorina citri Kuwayama nymphs were examined. Thermal performance curves for immature stages of D. citri were characterized using one linear and six nonlinear models (i.e., Ratkowsky, Lobry-Rosso-Flandrois, Lactin-2, Brière-2, Beta, and Performance-2). Daily thermal fluctuations had significant effects on development times of D. citri nymphs, which differed across experimental temperatures. Diaphorina citri nymphs reared at constant temperatures completed development faster than those reared under fluctuating profiles with equivalent temperature means. Linear model estimates of degree-days required for completion of cumulative development of D. citri were 25% lower for constant temperatures when compared with fluctuating temperature regimens. Nonlinear model estimations of optimum developmental temperature and upper theoretical temperature bounds for development were similar for individuals reared under constant and fluctuating temperatures. Nevertheless, the estimated values of lower theoretical temperature limits above which development occurred were lower under fluctuating than constant temperatures. A meta-analysis of published D. citri temperature-dependent development literature, synthesizing datasets of five globally distributed populations (Brazil, California, China, Florida, and Japan) reared under different constant temperatures on six different host plants (i.e., Citrus limonia, C. sinensis cv Natal, C. sinensis cv. Pêra, C. reticulata, Fortunella margarita, and Murraya paniculata), together with the results of this study (C. volkameriana), revealed convergence in estimates of developmental parameters. These results have implications for predicting D. citri invasion and establishment risk and subsequent population performance across various climactic gradients and geographic regions.

Surviving the Antarctic winter-Life Stage Cold Tolerance and Ice Entrapment Survival in The Invasive Chironomid Midge Eretmoptera murphyi

An insect’s ability to tolerate winter conditions is a critical determinant of its success. This is true for both native and invasive species, and especially so in harsh polar environments. The midge Eretmoptera murphyi (Diptera, Chironomidae) is invasive to maritime Antarctic Signy Island, and the ability of fourth instar larvae to tolerate freezing is hypothesized to allow the species to extend its range further south. However, no detailed assessment of stress tolerance in any other life stage has yet been conducted. Here, we report that, although larvae, pupae and adults all have supercooling points (SCPs) of around −5 °C, only the larvae are freeze-tolerant, and that cold-hardiness increases with larval maturity. Eggs are freeze-avoiding and have an SCP of around −17 °C. At −3.34 °C, the CT_min activity thresholds of adults are close to their SCP of −5 °C, and they are likely chill-susceptible. Larvae could not withstand the anoxic conditions of ice entrapment or submergence in water beyond 28 d. The data obtained here indicate that the cold-tolerance characteristics of this invasive midge would permit it to colonize areas further south, including much of the western coast of the Antarctic Peninsula.

Assessment of small sensory fiber function in myotonic dystrophy type 1

BACKGROUND

Myotonic dystrophy type 1 (DM1) is a multisystem disorder affecting the peripheral nervous system. However, studies evaluating somatic small fiber sensory nerve function, which may contribute to pain in DM1, are lacking.

METHODS

Using quantitative sensory testing of the hand and foot, we evaluated Aδ and C-fiber function. Of 20 adult DM1 patients recruited, 16 were analyzed. Their results were compared with those of 32 age- and sex-matched controls.

RESULTS

No DM1 patient had diabetes mellitus or clinical evidence of small fiber neuropathy. In DM1, hand (P < .01) and foot (P = 0.02) warm detection thresholds were higher than those of controls. Cool detection thresholds were lower in the foot (P < .001).

CONCLUSIONS

Subclinical small sensory fiber dysfunction occurs in DM1 patients without large fiber neuropathy. Further research with other modalities is required to characterize these disturbances as disease modifying therapies are developed.

Quantitative sensory testing in children with sickle cell disease: additional insights and future possibilities

Quantitative sensory testing (QST) is used in a variety of pain disorders to characterize pain and predict prognosis and response to specific therapies. In this study, we aimed to confirm results in the literature documenting altered QST thresholds in sickle cell disease (SCD) and assess the test-retest reliability of results over time. Fifty-seven SCD and 60 control subjects aged 8-20 years underwent heat and cold detection and pain threshold testing using a Medoc TSAII. Participants were tested at baseline and 3 months; SCD subjects were additionally tested at 6 months. An important facet of our study was the development and use of a novel QST modelling approach, allowing us to model all data together across modalities. We have not demonstrated significant differences in thermal thresholds between subjects with SCD and controls. Thermal thresholds were consistent over a 3- to 6-month period. Subjects on whom hydroxycarbamide (HC) was initiated shortly before or after baseline testing (new HC users) exhibited progressive decreases in thermal sensitivity from baseline to 6 months, suggesting that thermal testing may be sensitive to effective therapy to prevent vasoocclusive pain. These findings inform the use of QST as an endpoint in the evaluation of preventative pain therapies.

Dissecting seed dormancy and germination in Aquilegia barbaricina, through thermal kinetics of embryo growth

Threshold-based thermal time models provide insight into the physiological switch from the dormant to the non-dormant germinating seed. This approach was used to quantify the different growth responses of the embryo of seeds purported to have morphophysiological dormancy (MPD) through the complex phases of dormancy release and germination. Aquilegia barbaricina seeds were incubated at constant temperatures (10-25 °C) and 25/10 °C, without pre-treatment, after warm+cold stratification (W+C) and GA₃ treatment. Embryo growth was assessed and the time of testa and endosperm rupture scored. Base temperatures (T_b ) and thermal times for 50% (θ₅₀ ) of embryo growth and seed germination were calculated. W+C enabled slow embryo growth. W+C and GA₃ promoted rapid embryo growth and subsequent radicle emergence. The embryo internal growth base temperature (T_be ) was ca. 5 °C for W+C and GA₃ -treated seeds. GA₃ treatment also resulted in similar T_b estimates for radicle emergence. The thermal times for embryo growth (θ_e50 ) and germination (θ_g50 ) were four- to six-fold longer in the presence of GA₃ compared to W+C. A. barbaricina is characterised by a multi-step seed germination. The slow embryo growth during W+C reflects continuation of the maternal programme of development, whilst the thermal kinetics of both embryo and radicle growth after the removal of physiological dormancy are distinctly different. The effects of W+C on the multiphasic germination response in MPD seeds are only partially mimicked by 250 mg·l^-1 GA₃ . The thermal time approach could be a valid tool to model thermal kinetics of embryo growth and radicle protrusion.

Effect of low-frequency deep brain stimulation on sensory thresholds in Parkinson's disease

OBJECTIVE Chronic pain is a major distressing symptom of Parkinson's disease (PD) that is often undertreated. Subthalamic nucleus (STN) deep brain stimulation (DBS) delivers high-frequency stimulation (HFS) to patients with PD and has been effective in pain relief in a subset of these patients. However, up to 74% of patients develop new pain concerns while receiving STN DBS. Here the authors explore whether altering the frequency of STN DBS changes pain perception as measured through quantitative sensory testing (QST). METHODS Using QST, the authors measured thermal and mechanical detection and pain thresholds in 19 patients undergoing DBS via HFS, low-frequency stimulation (LFS), and off conditions in a randomized order. Testing was performed in the region of the body with the most pain and in the lower back in patients without chronic pain. RESULTS In the patients with chronic pain, LFS significantly reduced heat detection thresholds as compared with thresholds following HFS (p = 0.029) and in the off state (p = 0.010). Moreover, LFS resulted in increased detection thresholds for mechanical pressure (p = 0.020) and vibration (p = 0.040) compared with these thresholds following HFS. Neither LFS nor HFS led to changes in other mechanical thresholds. In patients without chronic pain, LFS significantly increased mechanical pain thresholds in response to the 40-g pinprick compared with thresholds following HFS (p = 0.032). CONCLUSIONS Recent literature has suggested that STN LFS can be useful in treating nonmotor symptoms of PD. Here the authors demonstrated that LFS modulates thermal and mechanical detection to a greater extent than HFS. Low-frequency stimulation is an innovative means of modulating chronic pain in PD patients receiving STN DBS. The authors suggest that STN LFS may be a future option to consider when treating Parkinson's patients in whom pain remains the predominant complaint.

Optimizing Nesidiocoris tenuis (Hemiptera: Miridae) as a biological control agent: mathematical models for predicting its development as a function of temperature

For optimal application of Nesidiocoris tenuis as a biological control agent, adequate field management and programmed mass rearing are essential. Mathematical models are useful tools for predicting the temperature-dependent developmental rate of the predator. In this study, the linear model and nonlinear models Logan type III, Lactin and Brière were estimated at constant temperatures and validated at alternating temperatures and under field conditions. N. tenuis achieved complete development from egg to adult at constant temperatures between 15 and 35°C with high survivorship (>80%) in the range 18-32°C. The total developmental time decreased from a maximum at 15°C (76.74 d) to a minimum at 33°C (12.67 d) and after that, increased to 35°C (13.98 d). Linear and nonlinear developmental models all had high accuracy (R a 2 >0.86). The maximum developmental rate was obtained between 31.9°C (Logan type III and Brière model for N1) and 35.6°C (for the egg stage in the Brière model). Optimal survival and the highest developmental rate fell within the range 27-30°C. The field validation revealed that the Logan type III and Lactin models offered the best predictions (95.0 and 94.5%, respectively). The data obtained on developmental time and mortality at different temperatures are useful for mass rearing this predator, and the developmental models are valuable for using N. tenuis as a biological control agent.