A Simple, Inexpensive Method for Mark-Recapture of Ixodid Ticks

Where are my nematodes? labelling and visualising entomopathogenic nematodes in vivo using carbon quantum dots

Identifying single or groups of animals has significantly advanced our understanding of animal biology and ecology. However, labelling is extremely difficult in small animals, like soil invertebrates. Due to the complexity of current methods, the dynamics and interactions of these populations are often studied indirectly. Labelling nematodes or microarthropods such as collembolans or soil acari has been challenging due to the high cost, potential toxicity, genetic modification requirements, cellular processes interference, and photobleaching. In this scenario, no methods can be applied to large numbers of microorganisms at once due to their mentioned practical and biological limitations and cost. In this work we show that quantum carbon dots (Cdots) are effective for labelling infective juveniles (IJs) of entomopathogenic nematodes (EPNs). In in vitro assays the IJs gradually acquired fluorescence, as Cdots accumulated in the lysosome-related organelles from their intestine cells, peaking at day 14, and with no lethal or sub-lethal effects on IJs. Fluorescence was clearly distinguishable from the natural auto-fluorescence of non-labelled IJs and persisted for months in IJs transferred to water. We and non-experts easily differentiated between similar species of EPNs and between two strains of S. feltiae placed in the same matrix (soil or water). We demonstrated for the first time the feasibility of labelling large numbers of IJs (hundreds of thousands/millions) with Cdots at minimal cost without any adverse effects for over a year. Our findings could be the starting point for detailed and large-scale field investigations on nematodes and other small organisms, allowing deeper understanding of their roles in soil ecosystems. This method provides a cost-effective and reliable tool for advancing research in the ecology of soil invertebrates, such as the interactions occurring in communities or between specific organisms, movement and dispersal, population dynamics or ecosystem services in a cryptic environment difficult to study.

Spatial and temporal activity patterns of Amblyomma americanum

BACKGROUND

Estimates of tick abundance and distribution are used to determine the risk of tick-host contact. Tick surveys provide estimates of distributions and relative abundance for species that remain stationary and wait for passing hosts (i.e. questing), but measures of tick populations may be less reliable for species that actively move in search of a host, such as Amblyomma americanum, the lone star tick (LST). Risk estimates for contact with adult LST require knowledge of the tick's spatial and temporal activity. Understanding the movement and the temporal patterns of host-seeking behavior will enhance risk assessment for LST.

METHODS

Using CO2-baited traps over a 2-year period, we collected wild adult LST in Oklahoma. We used mark-recapture techniques to determine the distance ticks will travel, the proportion of the tick population that is detectable over time, and the relationship between tick abundance and the number of ticks detected in the field. Using video tracking software, we measured the distance traveled and activity time in the laboratory.

RESULTS

In 24 h, LST travel up to 9 (mean = 3.2, SD = 3.6) m in the field and 36 (mean = 70.4, SD = 81.0) m in the laboratory. Marked LST were detectable in the environment for up to 14 days after release. We found that the number of recaptured ticks significantly increased with the relative abundance of ticks released, and at a minimum abundance (N = 1 tick released) LST were detectable 33.3% of the time. Across all experiments, fewer than half of marked ticks were recovered and at most 28.4% of ticks were detected with CO2-baited traps at any given time.

CONCLUSIONS

Our results show that LST actively move through the environment and pose a risk for host contact at distances of tens of meters. Ticks are detectable for several weeks, but only a fraction of them are detectable at any time. Larger numbers of ticks are detected as their population size increases, but even at very low numbers, LST are recovered with CO2 baiting. These spatial and temporal aspects of LST behavior should be considered when building predictive risk models of LST-host contact.

Knowledge and perception of equine ticks and tick-borne diseases of Pennsylvania horse owners and caretakers

There is limited data on current knowledge of Pennsylvania horse caretakers on tick-borne diseases (TBDs), tick identification, and tick management practices. This study aimed to determine tick knowledge, concern, and management among Pennsylvania equine caretakers using an online survey. Descriptive statistics and one-way ANOVA tests were used to analyze data. The survey received 894 responses (539 completed) from Pennsylvania equine owners and caretakers. The largest proportion of respondents cared for 3-5 horses (31 %), followed by 2 horses (27 %). Veterinarian-confirmed diagnosis rates of two TBDs, Lyme disease and anaplasmosis, were 38 % and 22 %, respectively. Most respondents (39 %) were moderately confident in recognizing Lyme disease, while most (44 %) were not confident at all in recognizing anaplasmosis. Most respondents (69 %) were either extremely or very concerned about their horses contracting any TBDs. Tick bite and TBD prevention methods used by equine caretakers included performing tick checks, using on-animal repellents, and conducting pasture/landscape management. Ten knowledge-based questions were asked, and the mean correct score was 3.97 ± 2.18 out of 10 possible points. There were significant positive associations between higher knowledge scores and previous veterinarian-confirmed equine Lyme disease diagnosis, higher concern level of TBDs, and higher frequency of tick checks. With increased equine TBD prevalence and high levels of horse owner concern about TBD, Extension educators should focus on teaching about TBDs and managing ticks on horses and farms.

An Effective Fluorescent Marker for Tracking the Dispersal of Small Insects with Field Evidence of Mark-Release-Recapture of Trissolcus japonicus

Understanding insect dispersal helps us predict the spread of insect pests and their natural enemies. Dispersal can be studied by marking, releasing, and recapturing insects, known as mark-release-recapture (MRR). MRR techniques should be convenient, economical, and persistent. Currently, there are limited options for marking small parasitoids that do not impact their fitness and dispersal ability. We evaluated commercially available fluorescent markers used in forensics. These fluorophores can easily be detected by ultraviolet (UV) light, requiring minimal costs and labor to process the marked specimens. This fluorophore marking technique was evaluated with the pest Drosophila suzukii and three parasitoids: Trissolcus japonicus, Pachycrepoideus vindemiae, Ganaspis brasiliensis (=G. kimorum). We evaluated the persistence of the marks on all the insects over time and examined the parasitoids for impacts on longevity, parasitism, locomotor activity, and flight take-off. The green fluorophore marker persisted for over 20 days on all four species. Marking generally did not consistently reduce the survival, parasitism rate, locomotor activity, or take-off of the parasitoids tested. Marked T. japonicus were recaptured in the field up to 100 m away from the release point and three weeks after release, indicating that this technique is a viable method for studying parasitoid dispersal.

Release the hens: a study on the complexities of guinea fowl as tick control

Established tick control strategies often involve methods that can be damaging to existing environmental conditions or natural host ecology. To find more environmentally friendly methods, biological controls, like predators of ticks, have been suggested. There are natural predators of ticks, but most are generalists and not expected to control tick populations. Helmeted guinea fowl (Numida meleagris (L.) (Galliformes: Numididae)) have been suggested to be biological controls of ticks, and therefore, tick-borne pathogens, but their potential role as hosts for ticks complicates the relationship. A study was conducted to assess whether guinea fowl reduces the abundance of lone star ticks, Amblyomma americanum (L.) (Acari: Ixodidae), or whether they are hosts of ticks. Using mark-recapture techniques, painted lone star ticks were placed into 3 different treatments: penned, excluded, and free range. The recapture rates of painted ticks were compared. There was a significant difference between excluded and free-range treatments, but not between excluded and penned or between free range and penned. To investigate the role of guinea fowl as hosts of ticks, coop floors were examined for engorged ticks. Engorged lone star nymphs that had fed on guinea fowl were found. Lastly, ticks collected were tested to identify the potential reduction in risk of tick-borne pathogens. This study found no evidence that guinea fowl are an effective biological control of lone star ticks or tick-borne pathogens, but they are hosts of lone star nymphs. Future studies are needed to assess the complex ecology of a biological control of ticks that is also a host.

The first comprehensive population size estimations for the highly endangered largest diving beetle Dytiscus latissimus in Europe

Dytiscus latissimus (Coleoptera Dytiscidae) is an endangered diving beetle throughout its range. It is one of the two species of Dytiscidae listed in Annex II of the Habitats Directive, IUCN red list and in many national level legislations and therefore strictly protected. The conservation of endangered species first of all requires an assessment of their population size. Until now, a method has not been developed for estimating the size of D. latissimus populations. The article summarizes the results of two studies carried out independently in Germany and Latvia. Both studies were carried out in one water body used recapture method but with a different spatial placement of traps, which, according to our data, is an important factor in population estimation. We evaluated Jolly-Seber and Schnabel approaches of estimating aquatic beetle's populations and found that confidence intervals obtained by different methods in our research do not differ significantly, but combination of both models provide the most accurate estimates of population dynamics. As part of the study, we concluded that the populations of Dytiscus latissimus are relatively closed, so we accept that the Schnabel estimate shows more accurate data. By fixing the places of capture of each individual, it was found that females live mainly locally, and males actively move within the water body. This aspect indicates the advantage of the spatial placement of traps compared to the use of transects. The results of our study show a significantly higher number of both captured and recaptured males Such a sex ratio may indicate both a greater activity of males and differences in the sex ratio in the population. The study confirmed that environmental changes, such as the water level in a water body, can also significantly affect the result of a population assessment. In the frame of D. latissimus monitoring, to obtain an objective estimation of the species population size we recommend using four traps for each 100 m of water body shoreline with 4-8 censuses, dependently on the recapture rate.

Effects of SmartWater, a fluorescent mark, on the dispersal, behavior, and biocontrol efficacy of Phytoseiulus persimilis

New marking methods for studying small biocontrol agents (especially predatory mites) are needed because many current techniques are expensive, ineffective or not applicable to small organisms. The objective of this study was to determine whether SmartWater, a liquid and permanent fluorescent dye, can be used to mark Phytoseiulus persimilis for experimentation without any deleterious effects on its dispersal, behavior, reproduction, and biocontrol efficacy. Our results show that there were no significant differences in movement, inter-plant dispersal, feeding behavior, survivability, and reproduction between marked P. persimilis and control individuals sprayed with water. We also found that the SmartWater mark lasted for the duration of the mites' life, indicating strong durability over time. Marking efficacy may be reduced, due to a trade-off between batch marking efficacy and the possibility of drowning study organisms. However, we feel future research could improve liquid marking techniques that would reduce this risk. Overall, this study concludes that SmartWater could be a useful marking tool for predatory mites in both laboratory and field studies.

Mark-release-recapture of ticks: A case study of estimating the abundance of Ixodes persulcatus (Acari, Ixodidae)

In this study, we tested the applicability of three common methods of absolute abundance estimation-Peterson, Bailey and Jolly-Seber-to Ixodes persulcatus ticks based on mark-release-recapture data. The ticks were collected by flagging during the seasonal activity peak of the ticks in the mid-taiga zone of Karelia (62.0697°N, 33.9614°E). In total, 108 females and 92 males of I. persulcatus were marked. The marked individuals were captured 161 times before the end of the study period with their proportion in the samples reaching 50%. Females were recaptured more often than males, 105 versus 56 times. Estimates of adult tick abundance ranged from 0.4 to 2 specimens per m² depending on the calculation method. The obtained estimates of absolute abundance varied unpredictably depending on the length of the intervals between capture sessions and showed no significant correlations with the number of ticks collected by flagging. The choice of the method of tick abundance estimation mainly depends on the study aims. The Petersen method may be useful for quick estimates of local tick abundance, whereas the Jolly-Seber method allows an estimation of the absolute abundance during the entire period of the tick activity. Individual marking of ticks may improve the accuracy of the estimates.