Consuming alternative prey does not influence the DNA detectability half-life of pest prey in spider gut contents

Background. Key natural enemy-pest interactions can be mapped in agricultural food webs by analysing predator gut content for the presence of a focal pest species. For this, PCR-based approaches are the most widely used methods providing the incidence of consumption of a focal pest in field sampled predators. To interpret such data the rate of prey DNA decay in the predators' gut, described by DNA detectability half-life (t(1/2)), is needed. DNA decay may depend on the presence of alternative prey in the gut of generalist predators, but this effect has not been investigated in one of the major predatory arthropod groups, spiders.Methods. In a laboratory feeding experiment, we determined t(1/2) of the key cereal pest virus vector leafhopper Psammotettix alienus in the digestive tracts of its natural enemy, the spider Tibellus oblongus. We followed the fate of prey DNA in spiders which received only the focal prey as food, or as an alternative prey treatment they also received a meal of fruit flies after leafhopper consumption. After these feeding treatments, spiders were starved for variable time intervals prior to testing for leafhopper DNA in order to establish t(1/2).Results. We created a PCR protocol that detects P. alienus DNA in its spider predator. The protocol was further calibrated to the digestion speed of the spider by establishing DNA decay rate. Detectability limit was reached at 14 days, where c. 10% of the animals tested positive. The calculated t(1/2) = 5 days value of P. alienus DNA did not differ statistically between the treatment groups which received only the leafhopper prey or which also received fruit fly. The PCR protocol was validated in a field with known P. alienus infestation. In this applicability trial, we showed that 12.5% of field collected spiders were positive for the leafhopper DNA. We conclude that in our model system the presence of alternative prey did not influence the t(1/2) estimate of a pest species, which makes laboratory protocols more straightforward for the calibration of future field data

Cool Headed Individuals Are Better Survivors: Non-Consumptive and Consumptive Effects of a Generalist Predator on a Sap Feeding Insect

Non-consumptive effects (NCEs) of predators are part of the complex interactions among insect natural enemies and prey. NCEs have been shown to significantly affect prey foraging and feeding. Leafhopper's (Auchenorrhyncha) lengthy phloem feeding bouts may play a role in pathogen transmission in vector species and also exposes them to predation risk. However, NCEs on leafhoppers have been scarcely studied, and we lack basic information about how anti-predator behaviour influences foraging and feeding in these species. Here we report a study on non-consumptive and consumptive predator-prey interactions in a naturally co-occurring spider-leafhopper system. In mesocosm arenas we studied movement patterns during foraging and feeding of the leafhopper Psammotettix alienus in the presence of the spider predator Tibellus oblongus. Leafhoppers delayed feeding and fed much less often when the spider was present. Foraging movement pattern changed under predation risk: movements became more frequent and brief. There was considerable individual variation in foraging movement activity. Those individuals that increased movement activity in the presence of predators exposed themselves to higher predation risk. However, surviving individuals exhibited a 'cool headed' reaction to spider presence by moving less than leafhoppers in control trials. No leafhoppers were preyed upon while feeding. We consider delayed feeding as a "paradoxical" antipredator tactic, since it is not necessarily an optimal strategy against a sit-and-wait generalist predator

Local hydrophobicity allows high-performance electrochemical carbon monoxide reduction to C 2+ products

Tailoring the hydrophobicity of the cathode gas diffusion electrode mitigates flooding in parallel with enhancing the selectivity of the electrochemical carbon monoxide reduction reaction

Photocatalytic and antimicrobial activity of sulfur functionalized TiO 2 containing composite films

Facile sulfation of TiO2 semiconductor photocatalyst was achieved by a simple grinding and calcination method using elemental sulfur from desulfurization of petroleum. The successful sulfation of the prepared visible-light-active photocatalyst was also proved by infrared and X-ray photoelectron spectroscopic measurements. Photocatalytic tests revealed that the most efficient member of the series has higher photocatalytic activity than TiO2 in the photodegradation of formic acid under both UV and visible-light activation. Moreover, the improved electrokinetic and water dispersibility behaviors of the sulfur-modified photocatalyst allowed the preparation of polyacrylate-based photoreactive thin films with increased photocatalytic activity, strong antimicrobial properties, and improved mechanical behavior

Local hydrophobicity allows high-performance electrochemical carbon monoxide reduction to C 2+ products

While CO can already be produced at industrially relevant current densities via CO2 electrolysis, the selective formation of C2+ products seems challenging. CO electrolysis, in principle, can overcome this barrier, hence forming valuable chemicals from CO2 in two steps. Here we demonstrate that a mass-produced, commercially available polymeric pore sealer can be used as a catalyst binder, ensuring high rate and selective CO reduction. We achieved above 70% faradaic efficiency for C2+ products formation at j = 500 mA cm−2 current density. As no specific interaction between the polymer and the CO reactant was found, we attribute the stable and selective operation of the electrolyzer cell to the controlled wetting of the catalyst layer due to the homogeneous polymer coating on the catalyst particles’ surface. These results indicate that sophistically designed surface modifiers are not necessarily required for CO electrolysis, but a simpler alternative can in some cases lead to the same reaction rate, selectivity and energy efficiency; hence the capital costs can be significantly decreased