Linoleic acid as corpse recognition signal in a social aphid

Social insect colonies constantly produce dead insects, which cause sanitary problems and potentially foster deadly pathogens and parasites. Hence, many social insects have evolved a variety of hygienic behaviors to remove cadavers from the colonies. To that end, they have to discriminate dead insects from live ones, where chemical cues should play important roles. In ants, bees and termites, such corpse recognition signals, also referred to as “death pheromones” or “necromones”, have been identified as fatty acids, specifically oleic acid and/or linoleic acid. Meanwhile, there has been no such report on social aphids. Here we attempted to identify the “death pheromone” of a gall-forming social aphid with second instar soldiers, Tuberaphis styraci, by making use of an artificial diet rearing system developed for this species. On the artificial diet plates, soldiers exhibited the typical cleaning behavior, pushing colony wastes with their heads continuously, against dead aphids but not against live aphids. GC-MS and GC-FID analyses revealed a remarkable increase of linoleic acid on the body surface of the dead aphids in comparison with the live aphids. When glass beads coated with either linoleic acid or body surface extract of the dead aphids were placed on the artificial diet plates, soldiers exhibited the cleaning behavior against the glass beads. A series of behavioral assays showed that (i) soldiers exhibit the cleaning behavior more frequently than non-soldiers, (ii) young soldiers perform the cleaning behavior more frequently than old soldiers, and (iii) the higher the concentration of linoleic acid is, the more active cleaning behavior is induced. Analysis of the lipids extracted from the aphids revealed that linoleic acid is mainly derived from phospholipids that constitute the cell membranes. In conclusion, we identified linoleic acid as the corpse recognition factor of the social aphid T. styraci. The commonality of the death pheromones across the divergent social insect groups (Hymenoptera, Blattodea and Hemiptera) highlights that these unsaturated fatty acids are generally produced by enzymatic autolysis of cell membranes after death and therefore amenable to utilization as a reliable signal of dead insects.

Wellbore Cleanness Under Total Losses in Horizontal Wells: The Field Study

In the Middle East many of the matured fields have fractured or vugular formations where the drilling is continued without return to a surface. This situation has been commonly interpreted as lack of hole cleaning and high risk of stuck pipe. The manuscript describes a study performed to analyze the hole cleaning while blind drilling horizontal sections. Most of the losses while drilling across fractured or vugular formations happen sudden, and this represents a risk of formation instability and stuck pipe. Additionally, the cuttings accumulation may lead to a potential pack off. To understand the hole cleaning the annular pressure while drilling was introduced in different sections, what via change of the equivalent static and dynamic densities describes the cutting and cavings accumulation in the annulus. Additionally, the hole cleaning behavior with different fluids pumped through the drillstring (i.e. drilling fluid, water, water with sweeps) was studied. The proposed study was performed in 4 different fields, 9 wells, across horizontal 6⅛-in. sections with total lost circulation. It was identified that while drilling with full returns ECD vs ESD variations are within 1.5 ppg, those variations are matching with the modeling of hydraulics. Once total losses encountered the variations between ECD and ESD are very low - within 0.2 ppg - indicating that annular friction losses below the loss circulation zone are minimal. This support the theory that all the drilled cuttings are properly lifted from bottom and carried to the karst into the loss circulation zone and not fluctuating above the loss zone. Additionally, minor to no relation found in hole cleaning while drilling with mud or a water with sweeps. This finding also is aligned with the stuck pipe statistics that shows higher incidents of stuck pipe while drilling the with full circulation due to pack off. The manuscript confirms the theory of the hole cleaning in total lost circulation and application of different hole cleaning practices to improve it. The results of the study can be implemented in any project worldwide.

Differing infection of Isaria fumosorosea (Wize) Brown & Smith in an aphid (Myzus persicae [Sulzer]) and predatory mite (Neoseiulus cucumeris [Oudemans]) under a scanning electron microscope

Implementing a predator-mediated pathogen dissemination system can meet the goal of simultaneous biocontrol of harmful mites and other pests. But for the system to be effective, it must satisfy the requirement of high lethality of the pathogen to the target pest(s) with low lethality to predatory mites in a suitable environment. Prior testing showed that the fungal entomopathogen Isaria fumosorosea (Wize) Brown & Smith exhibited high toxicity to aphids yet low toxicity to the predatory mite Neoseiulus cucumeris (Oudemans). In practical application, the humidity conditions of conidia carried by predatory mites to plants are not necessarily constant. Therefore, we set two different humidity conditions to observe the changes of spore attachment quantity and the differences of germination and infection between predatory mites and aphids after their bodies were stained with spores. Under 50±1% relative humidity (RH), predatory mites cleaned most spores in a short time; 24 hours after dusting, the number of spores (mean ± SD) on body was (0.64±0.10)×103, just (4.43±0.35)% of that at 0h, but spores on aphids were kept (16.58±1.48)% ((6.46±0.91)×103 spores) of that at beginning. There was a significant difference in the percentage of spores retained on aphids and predatory mites (p=0.000<0.01). Humidity could affect the cleaning behavior; under 95± 1% RH (the suitable humidity for conidia germination), more spores persisted than that under the 50 ± 1% RH condition; at 24h, the numbers of spores on each predatory mite and aphid were (1.00±0.10)×103 and (10.02±2.87)×103. Here, under a scanning electron microscope, we found that spores on the aphid’s body germinated 36 hours after dusting under 95± 1% RH, and the I. fumosorosea mycelium had spread after 48 hours; many new mycelium and spores were produced after 72 hours. In stark contrast, few spores germinated on the mite’s body, thus leading to very little damage to its surface. Different cleaning behavior and different morphological structure of body wall can both affect the attachment and infection of I. fumosorosea to aphids and predatory mites. In the future, chemical substance, enzyme and other factors should also be researched to explain the difference of infection of entomopathogenic fungi to different species.