Nymphs of the common bed bug (Cimex lectularius) produce anti-aphrodisiac defence against conspecific males

Background: Abdominal wounding by traumatic insemination and the lack of a long distance attraction pheromone set the scene for unusual sexual signalling systems. Male bed bugs (Cimex lectularius) mount any large, newly fed individual in an attempt to mate. Last instar nymphs overlap in size with mature females, which make them a potential target for interested males. However, nymphs lack the female's specific mating adaptations and may be severely injured by the abdominal wounding. We, therefore, hypothesized that nymphs emit chemical deterrents that act as an honest status signal, which prevents nymph sexual harassment and indirectly reduces energy costs for males. Results: Behavioural mating assays showed that males mount nymphs significantly shorter time compared to females, although initial mounting preference was the same. In support of our hypothesis, nymphs experienced the same percentage of mating with sperm transfer as females if they were unable to emit (E)-2-hexenal, (E)-2-octenal 4-oxo-(E)-2-hexenal and 4-oxo-(E)-2-octenal, from their dorsal abdominal glands. We report that the aldehydes and 4-oxo-(E)-2-hexenal are detected by olfactory receptor neurons housed in smooth and grooved peg sensilla, respectively, on the adult antennae, at biologically relevant concentrations. Behavioural experiments showed that application of 4-oxo-(E)-2-hexenal or the two aldehydes at a nymph-emitted ratio, to a male/female pair during mounting initiation, decreased mating frequency to a rate comparable to that of a male/nymph pair. Conclusions: By combining behavioural and sensory studies, we show that the nymph-specific alarm pheromone plays an important role in intra-specific communication in the common bed bug. Alarm pheromones are commonly looked upon as a system in predator/prey communication, but here we show that alarm pheromones may be used as multipurpose signals such as decreasing the risk of nymphal mating by males

Olfactory and behavioural responses of tsetse flies, Glossina spp., to rumen metabolites

Herbivores provide tsetse flies with a blood meal, and both wild and domesticated ruminants dominate as hosts. As volatile metabolites from the rumen are regularly eructed with rumen gas, these products could serve tsetse flies during host searching. To test this, we first established that the odour of rumen fluid is attractive to hungry Glossina pallidipes in a wind tunnel. We then made antennogram recordings from three tsetse species (G.pallidipes morsitans group, G.fuscipes palpalis group and G.brevipalpis fusca group) coupled to gas chromatographic analysis of rumen fluid odour and of its acidic, mildly acidic and neutral fractions. This shows tsetse flies can detect terpenes, ketones, carboxylic acids, aliphatic aldehydes, sulphides, phenols and indoles from this biological substrate. A mixture of carboxylic acids at a ratio similar to that present in rumen fluid induced behavioural responses from G.pallidipes in the wind tunnel that were moderately better than the solvent control. The similarities in the sensory responses of the tsetse fly species to metabolites from ruminants demonstrated in this study testify to a contribution of habitat exploitation by these vertebrates in the Africa-wide distribution of tsets

How do Digital Platforms Organize Immaturity: Towards an Integrative Framework for Platform Power

The power of digital platforms is increasingly raising concern in civil society and in policy circles. A recent surge of research has separately documented various forms of platform power and power abuse. However, there are surprisingly scant attempts in providing a holistic perspective on platform power. We address this issue by developing a socio-symbolic perspective on platforms’ power dynamics, and by asking the guiding question of how platforms organize immaturity. Drawing on Bourdieu’s concepts of field, capitals, and habitus, we explain how socio-symbolic structures shape power relations and transform the field in which platforms operate. We characterize the digital habitus and identify three stages in field transformation, each explained by the predominance of specific forms of power. Our analysis derives that while a subset of these forms of power increase organized immaturity, another subset can also empower the field’s actors. Thus, we make two main contributions: (1) We develop a novel socio-symbolic view of platforms’ power dynamics and an integrative framework conceptualizing the multifaceted dimension of platform power. (2) We exploit and enrich the concept of organized immaturity

How Digital Platforms Organize Immaturity: A Socio-Symbolic Framework of Platform Power

The power of the digital platforms and the increasing scope of their control over individuals and institutions have begun to generate societal concern. However, the ways in which digital platforms exercise power and organize immaturity—defined as the erosion of the individual’s capacity for public use of reason—have not yet been theorized sufficiently. Drawing on Bourdieu’s concepts of field, capitals, and habitus, we take a socio-symbolic perspective on platforms’ power dynamics, characterizing the digital habitus and identifying specific forms of platform power and counter-power accumulation. We make two main contributions. First, we expand the concept of organized immaturity by adopting a sociological perspective, from which we develop a novel socio-symbolic view of platforms’ power dynamics. Our frame-work explains fundamental aspects of immaturity, such as self-infliction and emergence. Sec-ond, we contribute to the platform literature by developing a three-phase model of platform power dynamics over time

Alarm Pheromones and Chemical Communication in Nymphs of the Tropical Bed Bug Cimex hemipterus (Hemiptera: Cimicidae)

The recent resurge of bed bug infestations (Cimex spp.; Cimicidae) and their resistance to commonly used pesticides calls for alternative methods of control. Pheromones play an important role in environmentally sustainable methods for the management of many pest insects and may therefore be applicable for the control of bed bugs. The tropical bed bug, Cimex hemipterus, is a temporary ectoparasite on humans and causes severe discomfort. Compared to the common bed bug, Cimex lectularius, little is known about the chemical signalling and pheromone-based behaviour of the tropical species. Here, we show that the antennal morphology and volatile emission of C. hemipterus closely resembles those of C. lectularius and we test their behavioural responses to conspecific odour emissions. Two major volatiles are emitted by male, female and nymph C. hemipterus under stress, (E)-2-hexenal and (E)-2-octenal. Notably, nymph emissions show contrasting ratios of these compounds to adults and are further characterized by the addition of 4-oxo-(E)-2-hexenal and 4-oxo-(E)-2-octenal. The discovery of this nymph pheromone in C. hemipterus is potentially the cause of a repellent effect observed in the bio-tests, where nymph odours induce a significantly stronger repellent reaction in conspecifics than adult odours. Our results suggest that pheromone-based pest control methods developed for C. lectularius could be applicable to C. hemipterus, with the unique nymph blend showing promising practical properties

Bed bug deterrence

A recent study in BMC Biology has determined that the immature stage of the bed bug (the nymph) signals its reproductive status to adult males using pheromones and thus avoids the trauma associated with copulation in this species. The success of this nymphal strategy of deterrence is instructive. Against the background of increasing problems with bed bugs, this research raises the question whether pheromones might be used to control them

Characterizing the scent and chemical composition of Panthera leo marking fluid using solid-phase microextraction and multidimensional gas chromatography–mass spectrometry-olfactometry

Lions (Panthera leo) use chemical signaling to indicate health, reproductive status, and territorial ownership. To date, no study has reported on both scent and composition of marking fluid (MF) from P. leo. The objectives of this study were to: 1) develop a novel method for simultaneous chemical and scent identification of lion MF in its totality (urine + MF), 2) identify characteristic odorants responsible for the overall scent of MF as perceived by human panelists, and 3) compare the existing library of known odorous compounds characterized as eliciting behaviors in animals in order to understand potential functionality in lion behavior. Solid-phase microextraction and simultaneous chemical-sensory analyses with multidimensional gas-chromatography-mass spectrometry-olfactometry improved separating, isolating, and identifying mixed (MF, urine) compounds versus solvent-based extraction and chemical analyses. 2,5-Dimethylpyrazine, 4-methylphenol, and 3-methylcyclopentanone were isolated and identified as the compounds responsible for the characteristic odor of lion MF. Twenty-eight volatile organic compounds (VOCs) emitted from MF were identified, adding a new list of compounds previously unidentified in lion urine. New chemicals were identified in nine compound groups: ketones, aldehydes, amines, alcohols, aromatics, sulfur-containing compounds, phenyls, phenols, and volatile fatty acids. Twenty-three VOCs are known semiochemicals that are implicated in attraction, reproduction, and alarm-signaling behaviors in other species

Más allá del Principio de Placer. Reflexiones en torno a la clínica psicoanalítica

El planteo de Sigmund Freud de la pulsión de muerte representa un abordaje teórico crucial para aproximarnos a entender algunas problemáticas con las que podemos encontrarnos en la labor clínica. En Más allá del principio de placer (1920/2001) Freud nos habla de una compulsión de repetición que responde a la firma de la pulsión de muerte, una repetición que actúa con la insistencia de inscribir algo, como un intento de simbolizar algo del orden de lo traumático. Se percata de que algo no satisface al principio de placer, examina la repetición de sueños en las neurosis traumáticas, que contradice la regla del principio de placer y se pregunta por qué hay en este caso una excepción. Hay una función restitutiva, que es la del principio de placer, pero también hay una función repetitiva. ¿Qué significa desde el punto de vista del principio de placer, el carácter inagotable de dicha reproducción? A partir de estas cuestiones intentaremos recorrer nuestro escrito, delimitando nuestra praxis como horizonte y punto de partida de la reflexiónFil: Harraca, María Florenci