Virus population extinction via ecological traps

Populations are at risk of extinction when unsuitable or when sink habitat exceeds a threshold frequency in the environment. Sinks that present cues associated with high-quality habitats, termed ecological traps, have especially detrimental effects on net population growth at metapopulation scales. Ecological traps for viruses arise naturally, or can be engineered, via the expression of viral-binding sites on cells that preclude viral reproduction. We present a model for virus population growth in a heterogeneous host community, parameterized with data from populations of the RNA bacteriophage Φ6 presented with mixtures of suitable host bacteria and either neutral or trap cells. We demonstrate that viruses can sustain high rates of population growth in the presence of neutral non-hosts as long as some host cells are present, whereas trap cells dramatically reduce viral fitness. In addition, we demonstrate that the efficacy of traps for viral elimination is frequency dependent in spatially structured environments such that population viability is a nonlinear function of habitat loss in dispersal-limited virus populations. We conclude that the ecological concepts applied to species conservation in altered landscapes can also contribute to the development of trap cell therapies for infectious human viruses.     

Universal Trap Timer Design to Examine Temporal Activity of Wildlife

Abstract: We designed a reliable and inexpensive universal trap timer that records the time from the moment a single-live-capture trap is triggered by an animal to when the observer checks the trap. Combined with trapping information, the diel activity pattern of a given species or demographic group can then be described or compared between imposed treatments. The universal trap timer is adaptable to operate reliably with most single-capture trap designs, requires no permanent modification of traps, and is easy to construct.     

The potential of flower odours for use in population monitoring of Western flower thrips Frankliniella occidentalis Perg. (Thysanoptera: Thripidae)

Sticky blue traps are a suitable and important tool for Western Flower Thrips population monitoring in greenhouses. They can be used in vegetables and in ornamentals, and provide important information on the current status of the pest population. However, such traps cannot be used in some susceptible plant species when they are flowering because at that stage the plants are more attractive to Western Flower Thrips than the traps. We therefore tried to increase trap attractiveness by combining the colour cue with an attractive odour cue. In laboratory experiments, we found a significant additive effect on attractiveness for two odours in traps provided with both the visual and the olfactory cues as compared to traps with either cue alone. However, these results could not easily be reproduced in greenhouses. The main factors responsible for this failure seem to be (1) the only moderate, additive increase of trap attractiveness when using combined visual and olfactory cues, and (2) the problems associated with odour diffusion. Unless a more attractive odour is found and a suitable odour dispenser is available, the use of odours to enhance sticky blue trap attractiveness for Western Flower Thrips cannot be recommended and, given the added cost for the trap, may not be affordable for growers.     

Induction of trap formation in nematode-trapping fungi by a bacterium

Three soil bacterial strains were identified as Chryseobacterium sp. TFB on the basis of their 16S rRNA gene sequences. Conidia of Arthrobotrys oligospora produced a few mycelial traps (MT) and conidial traps (CT) when cultured with bacterial cells that they did not produce when cultured with a bacterial cell-free culture filtrate. However, co-culture of A. oligospora with bacterial cells and bacteria-free filtrate simultaneously induced MT and CT in large amounts. With the increased concentration of bacteria-free filtrate, the number of typical CT increased, but conidial germination was progressively inhibited. Scanning electron microscopy of A. oligospora co-cultured with bacteria revealed that bacterial attachment to hyphae was a prerequisite to trap formation and that bacteria-free filtrate facilitated bacterial attachments to hyphae. The results that the addition of nutrients in co-culture medium decreased the number of traps suggest that this type of trap formation may be favoured at a low nutrient status. Eight fungi tested were able to form MT and CT when co-cultured with bacterial cells and bacteria-free culture filtrate, but the abilities varied among species. This study provides novel evidence that under laboratory conditions, soil bacteria attaching to hyphae could induce traps in nematode-trapping fungi.     

Minimizing Leg-Hold Trapping Trauma for Otters With Mobile Phone Technology

ABSTRACT We present and evaluate a protocol for the capture of otters (Lutra lutra) using padded leg-hold traps coupled with Global System for Mobile communication (GSM) trap alarms. The trapping method was highly efficient, capturing 46 otters at 6.9 trap-nights each. Functioning alarms allowed us to remove 36 otters from their traps within 22 (SD = 14) minutes of capture. We caught 10 otters in trap sets with malfunctioning trap alarms and retrieved them the following morning, after ≤24 hours. Functioning alarms reduced the injuries suffered from an average cumulative score of 77.7 to just 5.5 on the International Organization for Standardization 10990-5 trauma scale (Z=-5.074, P ≤ 0.001). As a result, we strongly encourage the use of GSM trap alarms under the principle of refinement in animal experiments.     

Enhanced gene trapping in mouse embryonic stem cells

Gene trapping is used to introduce insertional mutations into genes of mouse embryonic stem cells (ESCs). It is performed with gene trap vectors that simultaneously mutate and report the expression of the endogenous gene at the site of insertion and provide a DNA tag for rapid identification of the disrupted gene. Gene traps have been employed worldwide to assemble libraries of mouse ESC lines harboring mutations in single genes, which can be used to make mutant mice. However, most of the employed gene trap vectors require gene expression for reporting a gene trap event and therefore genes that are poorly expressed may be under-represented in the existing libraries. To address this problem, we have developed a novel class of gene trap vectors that can induce gene expression at insertion sites, thereby bypassing the problem of intrinsic poor expression. We show here that the insertion of the osteopontin enhancer into several conventional gene trap vectors significantly increases the gene trapping efficiency in high-throughput screens and facilitates the recovery of poorly expressed genes.     

How the type of anthropogenic change alters the consequences of ecological traps

Understanding altered ecological and evolutionary dynamics in novel environments is vital for predicting species responses to rapid environmental change. One fundamental concept relevant to such dynamics is the ecological trap, which arises from rapid anthropogenic change and can facilitate extinction. Ecological traps occur when formerly adaptive habitat preferences become maladaptive because the cues individuals preferentially use in selecting habitats lead to lower fitness than other alternatives. While it has been emphasized that traps can arise from different types of anthropogenic change, the resulting consequences of these different types of traps remain unknown. Using a novel model framework that builds upon the Price equation from evolutionary genetics, we provide the first analysis that contrasts the ecological and evolutionary consequences of ecological traps arising from two general types of perturbations known to trigger traps. Our model suggests that traps arising from degradation of existing habitats are more likely to facilitate extinction than those arising from the addition of novel trap habitat. Importantly, our framework reveals the mechanisms of these outcomes and the substantial scope for persistence via rapid evolution that may buffer many populations from extinction, helping to resolve the paradox of continued persistence of many species in dramatically altered landscapes.     

Optical trapping in animal and fungal cells using a tunable, near-infrared titanium-sapphire laser

We have compared two different laser-induced optical light traps for their utility in moving organelles within living animal cells and walled fungal cells. The first trap employed a continuous wave neodymium-yttrium aluminum garnet (Nd-YAG) laser at a wavelength of 1.06 micron. A second trap was constructed using a titanium-sapphire laser tunable from 700 to 1000 nm. With the latter trap we were able to achieve much stronger traps with less laser power and without damage to either mitochondria or spindles. Chromosomes and nuclei were easily displaced, nucleoli were separated and moved far away from interphase nuclei, and Woronin bodies were removed from septa. In comparison, these manipulations were not possible with the Nd-YAG laser-induced trap. The optical force trap induced by the tunable titanium-sapphire laser should find wide application in experimental cell biology because the wavelength can be selected for maximization of force production and minimization of energy absorption which leads to unwanted cell damage.     

A new trap and lure for Drosophila melanogaster (Diptera: Drosophilidae)

We conducted a series of nine laboratory experiments testing the response of "vinegar flies," Drosophila melanogaster Meigen (Diptera: Drosophilidae), released in bioassay chambers to experimental traps and lures. These experiments showed that an effective trap could be constructed from a clear 225-ml screw-cap jar fitted with a hollow 8-mm-diameter cylindrical cross bridge. Flies could enter the trap from either end of the cylindrical "gate" and in turn could enter the interior chamber of the trap through a cut out portion at mid-span of the cylinder. The experiments also showed that a natural-component lure could be made using a teabag containing freeze-dried banana powder, yeast, and carrageenan gum powder as a humectant. When dipped in water for 10-15 s and then placed in the bottom of a trap, the teabag provided effective attraction for at least 7 d. Captured flies were immobilized on a sticky card placed in the trap, allowing them to be easily seen. Unlike other traps that cannot be opened and have liquid lures, the cylindrical-gate trap can be reused repeatedly if the teabag and sticky card are replaced. A final two experiments showed that the prototype operational cylindrical-gate trap with a teabag lure captured 3.3 and 2.3 times more released flies, respectively, than the next best of three commercially available traps.     

Evaluation of trap types and food attractants for Rhagoletis cerasi (Diptera: Tephritidae)

Trapping experiments were conducted during the period of flight activity of the cherry fruit fly Rhagoletis cerasi L. in the area of Thessaloniki, northern Greece, during the years 1993-1997 to test several traps alone and in combination with different food attractants. Yellow sticky-coated visual traps were more effective than McPhail-type traps baited with different food attractants. Of the visual traps, the most effective was the yellow Rebell trap. The Rebell trap, provided with a dispenser containing a slow release formulation of ammonium acetate attached to the lower part of the trap, was found to be the most effective of all treatments tested, capturing approximately 50% more R. cerasi flies than the Rebell trap without any attractant. Ammonium carbonate dispensers did not increase the performance of Rebell traps. More mature females were captured in Rebell traps baited with or without ammonium acetate than in McPhail-type traps baited with ammonium acetate. This study demonstrates that Rebell traps baited with an ammonium acetate dispenser can provide a more effective tool for monitoring and mass trapping of R. cerasi than the currently used unbaited Rebell traps.     

Inducible gene trapping with drug-selectable markers and Cre/loxP to identify developmentally regulated genes

Gene trapping in mouse embryonic stem cells is an important genetic approach that allows simultaneous mutation of genes and generation of corresponding mutant mice. We designed a selection scheme with drug selection markers and Cre/loxP technology which allows screening of gene trap events that responded to a signaling molecule in a 96-well format. Nine hundred twenty gene trap clones were assayed, and 258 were classified as gene traps induced by in vitro differentiation. Sixty-five of the in vitro differentiation-inducible gene traps were also responsive to retinoic acid treatment. In vivo analysis revealed that 85% of the retinoic acid-inducible gene traps trapped developmentally regulated genes, consistent with the observation that genes induced by retinoic acid treatment are likely to be developmentally regulated. Our results demonstrate that the inducible gene trapping system described here can be used to enrich in vitro for traps in genes of interest. Furthermore, we demonstrate that the cre reporter is extremely sensitive and can be used to explore chromosomal regions that are not detectable with neo as a selection cassette.     

Measuring trap efficiency for bark beetles (Col., Scolytidae)

Abstract:  The relative efficiency of cylindrical, linear and cross-barrier traps for trapping bark beetles was investigated based on a theoretical model. Using this model, the effective trap interception area of each trap type was calculated and trap efficiency was defined as the ratio of the effective interception area to the trap surface area. The relative efficiencies of the three trap types were calculated as the ratios of their respective effective interception areas. Based on this approach, assuming random directional movement of dispersing beetles, the order of efficiency of the three trap types, from highest to lowest, was linear, cross-barrier and cylindrical. The expected ratios of trap catches based on the relative efficiencies of the three trap types were fitted to data from trapping experiments with the mountain pine beetle ( Dendroctonus ponderosae Hopkins). In general, there was large variation in trap catches among traps of the same type but the ratios of mean catches per trap conformed to the expected ratios. The results indicate that the model of trap efficiency could be used for designing efficient traps. The methods presented are amenable for assessing the efficiency of other trap designs.     

Use of a Low-Frequency Esr Spectrometer: Implications for Spin-Trapping Free Radicals, In Situ

We have adapted the low-frequency ESR spectrometer, designed and built by H.J. Halpern, to the physiologic needs of organ preparations operating at 250 MHz. Initial studies have allowed us to detect nitroxides in an isolated perfused heart. These in siru measurements were made with nitroxides specifically designed to mimic the lipophilic nature of 5,5-dimethyl-l-pyrroline-l-oxide (DMPO) and 2.2-dimethyl-S-hydroxy-l-pyrrolidinyloxyl (DMPO-OH). These spin labels provided information about the influence of dynamic factors of the heart, such as flow rate, different cell populations and unequal distribution between compartments on our ability to conduct and interpret spin trapping experiments. They also clarified the sacrifice in sensitivity involved in operating at the lower frequencies. To deal with this later problem. we have increased the sensitivity of the spin trapping method by synthesizing a family of ¹⁵N-and deuterium-containing DMPO analogs and by determining their ability to spin trap free radicals generated by the model superoxide system of xanthinelxanthinc oxidase. Finally, since activated neutrophils are one of the few cells known to generate free radicals as part of their physiologic function, we used these phagocytic cells, as a source of superoxide.     

Efficiency of flight interception traps for adult Colorado potato beetles (Coleoptera: Chrysomelidae)

Interception traps have been used to monitor and sample Colorado potato beetle, Leptinotarsa decemlineata (Say), populations in flight, but the efficiency of these traps was unknown. The efficiency of interception window traps is limited because flying adults avoid the traps and may bounce off the trap without being collected. All trap types tested were avoided in flight chamber tests, including those constructed of transparent Plexiglas or yellow wood boards. A larger screen trap and a harp trap designed to reduce detection were also avoided by the beetles in flight. None of the traps provide a direct estimate of the number of adults randomly flying in the trap area. The highest level of efficiency for window traps was obtained with the yellow trap, which caught 16% of the expected flying population. Harp and screen traps without frames intercepted 60-62% of the expected flying population. The presence of a frame did not increase significantly the avoidance of the screen and harp traps by beetles in flight. Recommendations are made to maintain or increase the efficiency of some traps.     

Secretion trap tagging of secreted and membrane-spanning proteins using Arabidopsis gene traps

Secreted and membrane-spanning proteins play fundamental roles in plant development but pose challenges for genetic identification and characterization. We describe a "secretion trap" screen for gene trap insertions in genes encoding proteins routed through the secretory pathway. The gene trap transposon encodes a beta-glucuronidase reporter enzyme that is inhibited by N-linked glycosylation specific to the secretory pathway. Treatment of seedlings with tunicamycin inhibits glycosylation, resulting in increased activity of secreted beta-glucuronidase fusions that result from gene trap integration downstream of exons encoding signal peptides. In the 2,059 gene trap lines that we screened, 32 secretion trap expression patterns were identified in a wide variety of tissues including embryos, meristems, and the developing vasculature. Genes disrupted by the secretion traps encode putative extracellular signaling proteins, membrane transport proteins, and novel secreted proteins of unknown function missed by conventional mutagenesis and gene prediction. Secretion traps provide a unique reagent for gene expression studies and can guide the genetic combination of loss of function alleles in related genes.     

Field evaluation of female attractants for monitoring Ceratitis capitata (Diptera: Tephritidae) under a range of climatic conditions and population levels in Western Australia

Field trials were conducted in Western Australia to compare captures of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), in a standard male-targeted trap (Lynfield trap baited with Capilure) with a synthetic, female-targeted attractant marketed as BioLure. BioLure was also compared with other fenale attractants (orange ammonia, liquid protein bait) and tested in plastic McPhail, Tephri, and Lynfield traps. The possibility of using one trap to monitor female and male C. capitata populations was also tested by combining BioLure in a trap with the male attractant, Capilure. The results of these experiments show that BioLure outperformed the female-targeted system currently used for monitoring female C. capitala (liquid protein in MePhail trap). More male C. capitata were caught in the standard male-targeted trap, but more females were caught in traps baited with BioLure irrespective of trap type, climate, host tree, or population level. Combined lure traps caught equivalent total numbers of C. capitata to the standard male-targeted trap, but fewer females were captured. Tephri traps caught more flies than McPhail traps, but McPhail traps caught equivalent proportions of females. We compared the performance in commercial orchards of the standard male-targeted trap with a female-targeted trap (McPhail with BioLure). We found that the male trap detected C. capitata more often, caught more flies, triggered the economic threshold more often (66% of the time) and was more cost effective. The male-targeted trap is recommended for use on commercial orchards if cost is limiting. However, using both male and female-targeted traps increases the chance of detecting flies and triggering the economic threshold level. The synthetic female attractant is recommended for replacement of protein hydrolysate lures and may be used in either Tephri or McPhail traps.     

An Efficient Pit-light Trap to Study Beetle Diversity

A new, highly efficient pit-light trap is described and results of experiments on its efficacy that were carried out in various types of forests are presented. The Luminoc® insect trap is made of two parts: a 1-L collection container inserted into the ground and an upper container which houses a 6-V lantern battery and a circuit for electronic control of a 1.8-W miniature fluorescent tube. A cover is fixed under the upper container to prevent rainwater from entering the collection container. The pit-light trap caught significantly more specimens, species and families of Coleoptera than passive pitfall traps. Many species of common families, such as Carabidae, Cantharidae, Curculionidae, Elateridae, Pyrochroidae, Scarabaeidae, Silphidae and Tenebrionidae were mainly caught in pit-light traps. Several species of uncommon families such as Byrrhidae, Melandryidae, Scraptiidae, Stenotrachelidae and Throscidae were caught only in pit-light traps. The light source increases the sampling area of a trap to include many micro-habitats, which makes pit-light traps more efficient tools that provide less variable results than the passive pitfall traps. The use of only three pit-light traps allows the capture of three times more 'abundant and common' species than any number of passive pitfall traps could provide. Thus, the pit-light trap allows an easier and more accurate characterization of Coleoptera communities than the passive pitfall trap. Because of its high efficacy, the pit-light trap should be considered as a standard tool to study, monitor and inventory beetle diversity.     

Odour-baited traps influence thrips capture in proximal unbaited traps in the field

Two field experiments examined the distance over which an attractant odour of a volatile chemical could influence thrips capture in proximal traps that were without the odour. In each experiment a star‐shaped array of water traps consisted of a centre trap with or without an odour surrounded by odourless traps at 0.5, 1, 2, 5, and 10 m in eight equally spaced radial arms 45° apart. Experiments ran for 47 h (centre trap: ethyl nicotinate) or 7 h (centre trap: ethyl isonicotinate). Each had four replicates. With ethyl nicotinate, more thrips were trapped in the centre‐baited traps than in the unbaited centre traps (63×, 7×, 98× and 200× for total thrips, Thrips tabaci Lindeman ♀, and Thrips obscuratus Crawford ♀and ♂, respectively) (Thysanoptera: Thripidae). More total thrips and T. tabaci♀ were trapped in the centre traps baited with ethyl isonicotinate than in unbaited centre traps (21× for both). For ethyl nicotinate, numbers of T. obscuratus in unbaited traps downwind from the baited centre trap declined by 50% within 0.4 m (♀) and 2 m (♂) and by 95% within 3 m (both ♀ and ♂) based on model predictions. For ethyl isonicotinate, numbers of T. tabaci in unbaited traps downwind from the baited centre trap declined by 50% within 1.3 m and by 95% within 10 m based on model predictions. Wind direction was an important factor in the degree and direction of thrips capture with the highest thrips capture downwind from the centre trap with odour. There was no increase in numbers of T. tabaci in any traps without odour in the ethyl nicotinate‐centred array. Differences in trapping patterns between thrips species and odours indicated that there were thrips species–odour specific interactions. Experiments examining differences between traps with and without a thrips attractant odour need to be designed very carefully to ensure meaningful results especially in enclosed and/or low‐wind indoor situations.