Floating of the lobes of mosquito (Aedes togoi) larva for respiration

Photoactivated 9-methylacridine destroys midgut tissues of Aedes aegypti larvae by targeting ROS-mediated apoptosis in the mitochondrial pathway of midgut cells

An aromatic ring-containing compound with a wide range of biological activities, 9-methylacridine (AD-9-Me) is a precursor for the synthesis of various drugs. However, its photoactivation properties and mechanism of damage as a photo activator against Aedes aegypti are unknown. The toxic effects of AD-9-Me on Aedes aegypti mosquitoes were determined under light and non-light conditions. The results showed that the toxicity of AD-9-Me to mosquito larvae was significantly higher than that of the dark treatment after 24 h of light exposure; AD-9-Me was mainly distributed in the midgut of larvae, after 24 h of treatment, it can cause an increase in calcium ion concentration, reactive oxygen species (ROS) eruption and ROS accumulation by blocking the ROS elimination pathway in midgut cells. This in turn caused an increase in protein carbonyl and malondialdehyde (MDA) content, a decrease in mitochondrial membrane potential (MMP), a disruption of the barrier function of midgut tissues, a significant decrease in midgut weight and chitin content, which induced the up-regulation of AeDronc, AeCaspase8 and AeCaspase7 genes, leading to apoptotic cell death. In this study, we confirmed that AD-9-Me has photoactivation activity and mainly acts on the midgut of mosquito larvae, which can generate a large amount of ROS in the cells of the midgut and induce apoptosis to occur, resulting in the disruption of the function of the tissues of mosquito larvae, accelerating the death and delaying the development of the mosquito larvae.

Comparative efficacy trials with alcohol added d-phenothrin formulations against Aedes aegypti under open-field condition

BACKGROUND

Evaporation inhibition of water-based space spray insecticides is necessary to prevent the drifting away of fog droplets and the release of insecticidal actives and to prolong suspension time. To address this problem, hygroscopic alcohols, namely propylene glycol and glycerol, were included as adjuvants in water-based d-phenothrin formulations. The performances of glycerol-added formulation (D1) and propylene glycol-added formulation (D2) in terms of droplet size and efficacy against larvae, pupae and adult Aedes aegypti in an open-field environment were examined and compared to the performance of a formulation without adjuvant (negative control).

RESULTS

No significant difference in droplet size was observed between the formulations and fogging methods. The efficacy of cold fogs was significantly higher than thermal fogs for all formulations. D2 was found to be most effective against adult Ae. aegypti, followed by D1 and the negative control. D1 and D2 provided complete knockdown and mortality in adult Ae. aegypti at 10 and 25 m for cold and thermal fogging, respectively. However, all d-phenothrin formulations possessed minimal efficacy on immature Ae. aegypti.

CONCLUSION

The incorporation of non-toxic alcohols as adjuvants in water-based space spray insecticides increased efficacy against adult Ae. aegypti, a major vector for dengue. Propylene glycol was discovered to induce higher adulticidal efficacy than glycerol. © 2023 Society of Chemical Industry.

Pomegranate Resembling Design of Starch Sago Beads Encapsulates Nanopyriproxyfen, Enabling Slow Release and Improved Bioactivity

Environmental contamination by intense insecticide usage is consistently proposed as a significant contributor to major hazards; further, disturbing non-target populations provoke a grave concern worldwide as they play essential roles in ecosystems. Pyriproxyfen is one of the most widely used pesticides; however, due to its probable toxicity, its global application in large amounts may result in water concentrations that exceed regulatory pollution thresholds. Herein, we describe nanopyriproxyfen-loaded sago beads (PPX-NCB) designed for the slow release of pyriproxyfen (PPX). Our design is inspired by the composite structure of sago beads, composed of several small beads resembling a pomegranate. The microscopic beads accumulate chitosan-PPX-nanomicelles cross-linked with tripolyphosphate via physical absorption, offering adequate room for water absorption and subsequent PPX release. PPX-NCB had distinct effects on the immature egg and larva of Anopheles stephensi, limiting embryonic development in the eggs while enhancing bioactivity. It affects the integument of larvae and alters the surface hydrocarbons of eggs and larvae. In addition, PPX-NCB demonstrates an improved safety profile in non-target Daphnia magna.

Staying Dry and Clean: An Insect's Guide to Hydrophobicity

Insects demonstrate a wide diversity of microscopic cuticular and extra-cuticular features. These features often produce multifunctional surfaces which are greatly desired in engineering and material science fields. Among these functionalities, hydrophobicity is of particular interest and has gained recent attention as it often results in other properties such as self-cleaning, anti-biofouling, and anti-corrosion. We reviewed the historical and contemporary scientific literature to create an extensive review of known hydrophobic and superhydrophobic structures in insects. We found that numerous insects across at least fourteen taxonomic orders possess a wide variety of cuticular surface chemicals and physical structures that promote hydrophobicity. We discuss a few bioinspired design examples of how insects have already inspired new technologies. Moving forward, the use of a bioinspiration framework will help us gain insight into how and why these systems work in nature. Undoubtedly, our fundamental understanding of the physical and chemical principles that result in functional insect surfaces will continue to facilitate the design and production of novel materials.

Complex Suspended Janus Droplets Constructed through Solvent Evaporation-Induced Phase Separation at the Air-Liquid Interface

Phase separation technology has attracted extensive scientific interest because of its intriguing structure changes during the phase separation process. Phase separation inside emulsion droplets in continuous surroundings has been well studied in recent years. Many investigations have also been conducted to study the droplet phase separation phenomena in noncontinuous surroundings. However, studies on the phase separation phenomena and the spreading behavior of suspended droplets at the air-liquid interface were rarely reported. In this study, PEGDA-glycerol suspended Janus droplets with a patchy structure were produced by utilizing solvent evaporation-induced droplet phase separation at the air-liquid interface. By altering the glycerol/PEGDA volume ratio, the initial proportion of ethanol, and the concentration of surfactants, suspended droplets with different morphologies can be achieved, which include filbert-shaped droplets (FSDs), half lotus seedpod single-phase Janus droplets (HLSDs), lotus seedpod single-phase Janus droplets (LSDs), lotus seedpod-shaped droplets (LSSDs), multiple-bulge droplets (MBDs), and half gourd-shaped droplets (HGSDs). A patchy structure was generated at the air-droplet interface, which was attributed to the Marangoni stresses induced by nonuniform evaporation. Furthermore, a modified spreading coefficient theory was constructed and verified to illustrate the phase separation at the air-droplet interface, which was the first research to predict the phase separation phenomena at the air-liquid interface via spreading coefficients theory. Moreover, we studied the factors that led to the droplets being able to float by designing the combined parameters, including three interfacial tensions and the equilibrium contact angles. Therefore, a simple and versatile strategy for creating suspended Janus droplets has been developed for the first time, which holds significant potential in a variety of applications for material synthesis, such as the electrospinning solution behavior when sprayed from the nozzle into the air.

Mosquitoes Larvicidal Activity of Ocimum kilimandscharicum Oil Formulation under Laboratory and Field-Simulated Conditions

Mosquitoes are vectors of many severe diseases, including malaria, yellow as well as dengue fever, and lymphatic filariasis. The use of synthetic chemical insecticides for mosquito control has been associated with resistance development and detrimental human, and ecological effects. For a safer alternative, the emulsified Ocimum kilimandscharicum oil formulation was evaluated for its larvicidal activity. The oil was analyzed by GC and GC/MS. The formulations were evaluated against third instar mosquito larvae in the laboratory and later compared with Bacillus thuringiensis subsp. israelensis against An. gambiae under field-simulated conditions. Thirty-nine compounds were identified in the oil, the main ones being D-camphor (36.6%) and limonene (18.6%). The formulation showed significant larval mortalities against An. gambiae and An. arabiensis larvae with LC50 of 0.07 and 0.31 ppm, respectively, at 24 h. Under the field-simulated trial, within 24 h, the formulation showed 98% mortality while Bti had achieved 54%. On day three, it caused 100% mortality while Bti achieved 76.5%. The high bioactivity and sublethal toxic effects to offspring of treated mosquito larvae, in terms of disruption of larval morphological aspects, suggest the high potential of the formulation as a botanical larvicide. The formulation, thus, may provide a valuable alternative for the effective and eco-friendly control of disease vectors.

Continuous, autonomous subsurface cargo shuttling by nature-inspired meniscus-climbing systems

Water-walking insects can harness capillary forces by changing their body posture to climb or descend the meniscus between the surface of water and a solid object. Controlling surface tension in this manner is necessary for predation, escape and survival. Inspired by this behaviour, we demonstrate autonomous, aqueous-based synthetic systems that overcome the meniscus barrier and shuttle cargo subsurface to and from a landing site and a targeted drop-off site. We change the sign of the contact angle of a coacervate sac containing an aqueous phase or of a hydrogel droplet hanging from the surface by controlling the normal force acting on the sac or droplet. The cyclic buoyancy-induced cargo shuttling occurs continuously, as long as the supply of reactants diffusing to the sac or droplet from the surrounding aqueous phase is not exhausted. These findings may lead to potential applications in autonomously driven reaction or delivery systems and micro-/milli-robotics.

Hydrophobic-hydrophilic crown-like structure enables aquatic insects to reside effectively beneath the water surface

Various insects utilise hydrophobic biological surfaces to live on the surface of water, while other organisms possess hydrophilic properties that enable them to live within a water column. Dixidae larvae reside, without being submerged, just below the water surface. However, little is known about how these larvae live in such an ecological niche. Herein, we use larvae of Dixa longistyla (Diptera: Dixidae) as experimental specimens and reveal their characteristics. A complex crown-like structure on the abdomen consists of hydrophobic and hydrophilic elements. The combination of these contrasting features enables the larvae to maintain their position as well as to move unidirectionally. Their hydrophobic region leverages water surface tension to function as an adhesive disc. By using the resistance of water, the hydrophilic region serves as a rudder during locomotion.

Suzuki, Takaku, Hariyama and colleagues report on a crown-like structure found on the heads of midge larvae. This structure, analysed using scanning electron microscopy and experimental methods, enables subsurface adhesion and aids in control of locomotion in this region of the water column.

Acoustic tracheal rupture provides insights into larval mosquito respiration

Acoustic larviciding (AL) occurs by exposing mosquito larvae to acoustic energy that ruptures their dorsal tracheal trunks (DTTs) by the expulsion of gas bubbles into the body. In studying this technique, we serendipitously identified undescribed anatomical and physiological respiratory features. The classical theory of respiration is that the siphon and DTTs play obligate roles in respiration. Our results contradict the accepted theory that culicine larvae respire via atmospheric gas exchange. We identified an undescribed tracheal occlusion (TO) at the posterior extremities the DTTs. The TOs appear necessary for the acoustic rupture of DTTs; this constriction prevents the escape of energized gas from the siphon and allows the tracheal system to be pressurized. With a pressurized isolated tracheal system, metabolic gas exchange directly with the atmosphere is unlikely and could mostly occur through the chitin and setae. Future studies are needed to explore respiration and elucidate the mechanisms of oxygen absorption and carbon dioxide elimination.

Hanging droplets from liquid surfaces

Natural and man-made robotic systems use the interfacial tension between two fluids to support dense objects on liquid surfaces. Here, we show that coacervate-encased droplets of an aqueous polymer solution can be hung from the surface of a less dense aqueous polymer solution using surface tension. The forces acting on and the shapes of the hanging droplets can be controlled. Sacs with homogeneous and heterogeneous surfaces are hung from the surface and, by capillary forces, form well-ordered arrays. Locomotion and rotation can be achieved by embedding magnetic microparticles within the assemblies. Direct contact of the droplet with air enables in situ manipulation and compartmentalized cascading chemical reactions with selective transport. Applications including functional microreactors, motors, and biomimetic robots are evident.

Circumventing surface tension: tadpoles suck bubbles to breathe air

The surface tension of water provides a thin, elastic membrane upon which many tiny animals are adapted to live and move. We show that it may be equally important to the minute animals living beneath it by examining air-breathing mechanics in five species (three families) of anuran (frog) tadpoles. Air-breathing is essential for survival and development in most tadpoles, yet we found that all tadpoles at small body sizes were unable to break through the water's surface to access air. Nevertheless, by 3 days post-hatch and only 3 mm body length, all began to breathe air and fill the lungs. High-speed macrovideography revealed that surface tension was circumvented by a novel behaviour we call 'bubble-sucking': mouth attachment to the water's undersurface, the surface drawn into the mouth by suction, a bubble 'pinched off' within the mouth, then compressed and forced into the lungs. Growing tadpoles transitioned to air-breathing via typical surface breaching. Salamander larvae and pulmonate snails were also discovered to 'bubble-suck', and two insects used other means of circumvention, suggesting that surface tension may have a broader impact on animal phenotypes than hitherto appreciated.

It's Not a Bug, It's a Feature: Functional Materials in Insects

Over the course of their wildly successful proliferation across the earth, the insects as a taxon have evolved enviable adaptations to their diverse habitats, which include adhesives, locomotor systems, hydrophobic surfaces, and sensors and actuators that transduce mechanical, acoustic, optical, thermal, and chemical signals. Insect-inspired designs currently appear in a range of contexts, including antireflective coatings, optical displays, and computing algorithms. However, as over one million distinct and highly specialized species of insects have colonized nearly all habitable regions on the planet, they still provide a largely untapped pool of unique problem-solving strategies. With the intent of providing materials scientists and engineers with a muse for the next generation of bioinspired materials, here, a selection of some of the most spectacular adaptations that insects have evolved is assembled and organized by function. The insects presented display dazzling optical properties as a result of natural photonic crystals, precise hierarchical patterns that span length scales from nanometers to millimeters, and formidable defense mechanisms that deploy an arsenal of chemical weaponry. Successful mimicry of these adaptations may facilitate technological solutions to as wide a range of problems as they solve in the insects that originated them.

Effects of oil-film layer and surfactant on the siphonal respiration and survivorship in the fourth instar larvae of Aedes togoi mosquito in laboratory conditions

Mosquitoes transmit various diseases; thus, controlling them is necessary to prevent mosquito-borne infections. Unlike flying adult mosquitoes, those in the immature stages are easy to control because of being restricted to their habitats found in an aquatic environment. In this study, we aimed to evaluate of respiration and survivorship in the larvae of Aedes togoi. The mechanism of actions of the oil-film layer and the surfactant as well as their effects on the siphonal respiration of submerged Aedes togoi larvae were analyzed by checking the survival time of mosquito larvae against oil-film layer and surfactant, and conducting experiments using a siphon-model. Compared with an impermeable membrane used for reference (762.4 min; average time in all cases), the survival time of mosquito larvae was 5% longer for the oil-film layer (808.1 min) and 40% longer for the surfactant (1086.9 min). The surface of the siphon was changed from hydrophobic to hydrophilic by addition of a surfactant. In addition, the surface tension and wettability have a significant influence on the opening and closing of siphon. This study would be helpful for understanding the basic mechanism of physical control measures for disturbing the siphonal respiration of mosquito larvae in a way of dissolved oxygen and surface tension. The present results would guide the establishment of effective control measures for mosquitoes.

Micro-computed tomography characterization of tissue engineering scaffolds: effects of pixel size and rotation step

Quantitative assessment of micro-structure of materials is of key importance in many fields including tissue engineering, biology, and dentistry. Micro-computed tomography (µ-CT) is an intensively used non-destructive technique. However, the acquisition parameters such as pixel size and rotation step may have significant effects on the obtained results. In this study, a set of tissue engineering scaffolds including examples of natural and synthetic polymers, and ceramics were analyzed. We comprehensively compared the quantitative results of µ-CT characterization using 15 acquisition scenarios that differ in the combination of the pixel size and rotation step. The results showed that the acquisition parameters could statistically significantly affect the quantified mean porosity, mean pore size, and mean wall thickness of the scaffolds. The effects are also practically important since the differences can be as high as 24% regarding the mean porosity in average, and 19.5 h and 166 GB regarding the characterization time and data storage per sample with a relatively small volume. This study showed in a quantitative manner the effects of such a wide range of acquisition scenarios on the final data, as well as the characterization time and data storage per sample. Herein, a clear picture of the effects of the pixel size and rotation step on the results is provided which can notably be useful to refine the practice of µ-CT characterization of scaffolds and economize the related resources.