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Abstract Seal lice, unique among insects, show remarkable adaptability to the extreme conditions of the deep sea. Evolving with their seal and sea lion hosts, they have managed to tolerate hypoxia, high salinity, low temperature, and elevated hydrostatic pressure. Given the diving capabilities of their mammalian hosts, which can reach depths of hundreds to thousands of meters, our study examines the morphological variation among closely related seal lice species infesting hosts with different maximum diving depths. In particular, our research reveals a significant morphological difference between lice associated with regular and deep-diving hosts, where lice from deep-diving hosts tend to be rounder. This could be an adaptation to withstand the high hydrostatic pressures found in the deep ocean. The rounded shape optimizes the louse’s ability to withstand external pressure by redistributing it over a larger ventral/dorsal plane. This in turn minimizes the internal energy required to support body deformations, thereby increasing the louse’s resilience in the deep sea environment.

Protein aggregation increases during aging and is a pathological hallmark of many age-related diseases. Protein homeostasis (proteostasis) depends on a core network of factors directly influencing protein production, folding, trafficking, and degradation. Cellular proteostasis also depends on the overall composition of the proteome and numerous environmental variables. Modulating this cellular proteostasis state can influence the stability of multiple endogenous proteins, yet the factors contributing to this state remain incompletely characterized. Here, we performed genome-wide CRISPRi screens to elucidate the modulators of proteostasis state in mammalian cells, using a fluorescent dye to monitor endogenous protein aggregation. These screens identified known components of the proteostasis network and uncovered a novel link between protein and lipid homeostasis. Increasing lipid uptake and/or disrupting lipid metabolism promotes the accumulation of sphingomyelins and cholesterol esters and drives the formation of detergent-insoluble protein aggregates at the lysosome. Proteome profiling of lysosomes revealed ESCRT accumulation, suggesting disruption of ESCRT disassembly, lysosomal membrane repair, and microautophagy. Lipid dysregulation leads to lysosomal membrane permeabilization but does not otherwise impact fundamental aspects of lysosomal and proteasomal functions. Together, these results demonstrate that lipid dysregulation disrupts ESCRT function and impairs proteostasis.

Immature mosquitoes are thought to breathe only atmospheric air through their siphons despite reports of prolonged submerged survival. We studied the survival of last-instar larvae of Aedes aegypti fully submerged at different temperatures and measured the oxygen consumption from air and water-dissolved larvae and pupae of this species under different conditions. Larvae survived much longer than expected, reaching 50% mortality only after 58, 10, and 5 days at 15°, 25°, and 35 °C, respectively. Larval to pupa molt was only observed in larvae with access to air, whereas individuals kept submerged never molted. Although most of the oxygen was obtained from the air, larvae obtained 12.72% of their oxygen from the water, while pupae took only 5.32%. In both media, temperature affected the respiration rate of the larvae, with relatively close Q10 values (1.56 and 1.83 for water and air, respectively). A similar pattern of O2 consumption was observed in Ae. albopictus, whose larvae obtained 12.14% of their oxygen from the water. The detailed quantification of oxygen consumption by mosquito larvae showed that water-dissolved oxygen is not negligible and physiologically relevant, challenging the idea that mosquito larvae only breathe atmospheric oxygen.

Os ingredientes de origem animal possuem uma boa composição aminoacidica, porém muitas vezes com grande variação quantitativa. Neste trabalho foi avaliada a substituição da farinha de carne e ossos suína por farelo de soja com e sem o uso de lisina sintética na alimentação de juvenis de carpa comum. Foi conduzido um experimento com duração de 35 dias. Utilizou-se 135 peixes em um sistema de recirculação de água. Foram testadas três dietas: DA (dieta com proteína animal), DV (dieta 100% vegetal) e DV1 (dieta DV suplementada com 1% de lisina sintética). Após o período experimental, foram estimados os seguintes parâmetros zootécnicos: peso médio, comprimento total e padrão, fator de condição, taxa de crescimento específico, ganho de peso relativo, sobrevivência e biomassa. Além disso, analisou-se a composição centesimal dos peixes, onde foi determinado o teor de gordura, matéria seca e matéria mineral da carcaça. Foi medida também a quantidade de glicose plasmática das carpas. Os resultados de peso, comprimento e ganho de peso relativo foram superiores nos peixes alimentados com a dieta DA. Os peixes alimentados com dietas vegetais apresentaram maiores valores de glicose. A dieta com fonte protéica de origem animal é a melhor opção para a alimentação de juvenis de carpa comum.

Purpose: The aim of this research is to understand how the social-economic context influences the transformative potential of the sharing economy (SE). Originality/value: The literature on SE is still fraught with uncertainty. We have found that there is a paradox between generating social benefits to the community versus increasing social inequality. Design/methodology/approach: Data were collected from documentary analysis, netnography, participant observation, and interviews. The data collected were analyzed in the light of the theoretical framework proposed by Wittmayer et al. (2019) for the analysis of narratives related to social innovation. Findings: The produced narratives differ in terms of the type of platform (profit and non-profit). We have found that, in non-profit platforms, the economic and social context does not influence the transformative potential guided by the SE; for-profit platforms, on the other hand, the narrative of ‘income opportunity’ is context-sensitive. The main contributions of the research are the use of a theoretical framework of social innovation to analyze the narratives of the SE and the observation of contextual differences about the phenomenon, which should lead platforms and governments (in their regulatory role) to have different views on SE. We conclude that the narratives of the SE are different. For-profit platforms either do not take part or contribute very little to the phe nomenon of social innovation as a transformative process and, in the contexts of greater social-economic vulnerability, it can be a mechanism of worsening social inequality. / Objetivo: O objetivo desta pesquisa foi compreender como os contextos econômicos e sociais influenciam no potencial transformador da economia compartilhada (EC). Originalidade/valor: A literatura referente ao tema da EC ainda é repleta de incertezas. Entre elas, verificamos que há um paradoxo entre a geração de benefícios sociais à comunidade e o aumento da desigualdade social. Design/metodologia/abordagem: Os dados foram coletados por meio de análise documental, netnografia, observação participante e entrevistas. A partir da coleta, analisaram-se os dados à luz do framework teórico proposto por Wittmayer et al. (2019) para o exame de narrativas ligadas à inovação social. Resultados: As narrativas produzidas diferem quanto ao tipo de plataforma (com e sem fins lucrativos). Verificamos que, nas plataformas sem fins lucrativos, os contextos econômicos e sociais não influenciam no potencial transformador orientado pela EC, diferentemente das plataformas com fins lucrativos, nas quais a narrativa “oportunidade de renda” é sensível ao contexto. As principais contribuições da pesquisa realizada consistem na utilização de um framework teórico da inovação social para analisar as narrativas da EC e na observação de diferenças contextuais sobre o fenômeno, o que deveria levar as plataformas e os governos (no seu papel regulador) a ter diferentes olhares sobre a EC. Concluímos que as narrativas da EC se apresentam diferentemente. As plataformas com poucos (ou sem) fins lucrativos se inserem no fenômeno da inovação social como um processo transformador e, nos contextos de maior vulnerabilidade econômico social, podem ser um mecanismo de agravamento da desigualdade social.

Insects are the most evolutionarily and ecologically successful group of living animals, being present in almost all possible mainland habitats; however, they are virtually absent in the ocean, which constitutes more than 99% of the Earth’s biosphere. Only a few insect species can be found in the sea but they remain at the surface, in salt marshes, estuaries, or shallow waters. Remarkably, a group of 13 species manages to endure long immersion periods in the open sea, as well as deep dives, i.e., seal lice. Sucking lice (Phthiraptera: Anoplura) are ectoparasites of mammals, living while attached to the hosts’ skin, into their fur, or among their hairs. Among them, the family Echinophthiriidae is peculiar because it infests amphibious hosts, such as pinnipeds and otters, who make deep dives and spend from weeks to months in the open sea. During the evolutionary transition of pinnipeds from land to the ocean, echinophthiriid lice had to manage the gradual change to an amphibian lifestyle along with their hosts, some of which may spend more than 80% of the time submerged and performing extreme dives, some beyond 2000 m under the surface. These obligate and permanent ectoparasites have adapted to cope with hypoxia, high salinity, low temperature, and, in particular, conditions of huge hydrostatic pressures. We will discuss some of these adaptations allowing seal lice to cope with their hosts’ amphibious habits and how they can help us understand why insects are so rare in the ocean.

All cells maintain ionic gradients across their plasma membranes, producing transmembrane potentials (Vmem). Mounting evidence suggests a relationship between resting Vmem and the physiology of non-excitable cells with implications in diverse areas, including cancer, cellular differentiation, and body patterning. A lack of non-invasive methods to record absolute Vmem limits our understanding of this fundamental signal. To address this need, we developed a fluorescence lifetime-based approach (VF-FLIM) to visualize and optically quantify Vmem with single-cell resolution in mammalian cell culture. Using VF-FLIM, we report Vmem distributions over thousands of cells, a 100-fold improvement relative to electrophysiological approaches. In human carcinoma cells, we visualize the voltage response to growth factor stimulation, stably recording a 10–15 mV hyperpolarization over minutes. Using pharmacological inhibitors, we identify the source of the hyperpolarization as the Ca2+-activated K+ channel KCa3.1. The ability to optically quantify absolute Vmem with cellular resolution will allow a re-examination of its signaling roles.

Abstract From the advancement of tilapia production in recent years, diets are sought that allow the maximum growth, improving health and fish quality. In this study growth, biochemical, hematological and oxidative parameters were evaluated of tilapia fed with increasing selenium levels: 0.53, 0.86, 1.04 and 1.22 mg kg-1. It was used 400 juveniles (initial weight = 36.51 ± 10.88 g), fed for six weeks. There was no effect of selenium on fish growth, biochemical and hematological parameters. In the oxidative parameters, there was an increase in non-protein thiols and a decrease in malondialdehyde levels, evidencing antioxidant effects of selenium. The diet selenium levels above 0.86 mg kg-1 improved the antioxidant system and does not affect to biochemical, hematological and growth parameters of tilapia juveniles.

RESUMOForam conduzidos dois experimentos em laboratório e em condições de campo para avaliação da eficiência térmica da embalagem Tetra Pak(r)como isolante térmico em escamoteadores aquecidos. No experimento em laboratório, foi utilizado o delineamento inteiramente ao acaso, adotando-se dois tratamentos (com e sem revestimento de embalagens Tetra Pak(r)) com 15 repetições (dias). O experimento em condições de campo foi conduzido na sala de maternidade de suínos. O delineamento foi inteiramente ao acaso, adotando-se dois tratamentos com 12 repetições. Os tratamentos foram: escamoteadores aquecidos com e sem revestimento interno com embalagem Tetra Pak(r). Foram medidos os dados de temperatura ambiente, umidade relativa do ar, temperatura superficial do piso, temperatura superficial da pele, comportamento e ganho de peso dos leitões lactentes. O uso da embalagem Tetra Pak(r)como isolante térmico no revestimento de escamoteadores manteve a temperatura ambiente confortável (32°C), proporcionando conforto térmico aos leitões lactentes.

Blood-sucking insects experience thermal stress at each feeding event on endothermic vertebrates. We used thermography to examine how kissing-bugs Rhodnius prolixus actively protect themselves from overheating. During feeding, these bugs sequester and dissipate the excess heat in their heads while maintaining an abdominal temperature close to ambient. We employed a functional-morphological approach, combining histology, µCT and X-ray-synchrotron imaging to shed light on the way these insects manage the flow of heat across their bodies. The close alignment of the circulatory and ingestion systems, as well as other morphological characteristics, support the existence of a countercurrent heat exchanger in the head of R. prolixus, which decreases the temperature of the ingested blood before it reaches the abdomen. This kind of system has never been described before in the head of an insect. For the first time, we show that countercurrent heat exchange is associated to thermoregulation during blood-feeding.

O estudo foi desenvolvido no Laboratório de Piscicultura do Departamento de Zootecnia da Universidade Federal de Santa Maria, com duração de oito semanas, de abril a junho de 2011. O objetivo foi definir o melhor nível de incorporação do resíduo de peixes na alimentação de juvenis de jundiá, em sistema de recirculação d'água, utilizando-se 450 alevinos de jundiás, com peso médio inicial de 7,2±0,27g. Foram testadas cinco diferentes dietas, em três repetições, com níveis diferentes (0; 3,75; 7,5; 15; e 30%) de incorporação de farinha de carcaça de jundiás com vísceras (FCJCV). As dietas continham, aproximadamente, 37% de PB e 3200kcal de EM/kg de dieta. Foram coletados dados de ganho em peso diário, sobrevivência, fator de condição, taxa de crescimento específico, conversão alimentar aparente, rendimento de carcaça, taxa de eficiência proteica e deposição de proteína e lipídio corporal. O maior ganho de peso foi para o nível 30% de inclusão de FCJCV, com peso final de 45,47g e ganho em peso diário de 0,68g/dia. A dieta com nível de 30% de inclusão de FCJCV apresentou melhores valores para taxa de crescimento específico (3,34%/dia), conversão alimentar aparente (1,05: 1), biomassa final 1.105,45g, deposição proteica corporal (64,9mg/dia), taxa de eficiência proteica (1,9) e coeficiente de retenção proteica (1,96%). Concluiu-se que a utilização de farinha de resíduos de processamento de jundiá no nível de 30% de inclusão na dieta foi a que apresentou maior eficiência no desenvolvimento de juvenis de jundiá.

Avaliou-se a utilização da ractopamina como promotor de crescimento para carpa húngara em experimento com 56 dias de duração, realizado em 12 tanques-rede de pequeno volume, utilizando-se 360 peixes com peso inicial de 18,64±1,25g. Foram testadas três quantidades de ractopamina, 7, 14 e 21ppm/kg, mais a dieta controle. Avaliaram-se o peso médio, o comprimento total, a altura, a taxa de crescimento específico e o fator de condição. Foram também analisadas a composição corporal, a deposição tecidual e a glicose plasmática dos peixes. Não foi observado efeito significativo da adição de ractopamina sobre as características de desempenho. Observou-se maior concentração de glicose, 61,67mg/dL, nos peixes alimentados sem a adição de ractopamina na dieta. A adição de ractopamina na dieta proporcionou maior quantidade de gordura corporal nos peixes e não afetou a quantidade de proteína. Conclui-se que a adição de ractopamina na dieta não é eficiente para juvenis de carpa húngara.

Para avaliar o desempenho, o metabolismo e a composição corporal de juvenis de jundiá (Rhamdia quelen) e de carpa húngara (Cyprinus carpio) alimentados com fontes energéticas vegetais, foi conduzido experimento de 60 dias. Três dietas compostas por aveia descascada, farelo de arroz desengordurado estabilizado (FADE) ou por farelo de trigo e milho (dieta-controle) foram ofertadas três vezes ao dia a 360 juvenis de jundiá (5,59±0,06g) ou de carpa húngara (5,82±0,14g) distribuídos em 18 tanques (280L), totalizando nove tanques por espécie. Não foram observadas diferenças significativas no desempenho das espécies estudadas. Em relação aos parâmetros metabólicos, as menores concentrações séricas de colesterol total no jundiá foram verificadas nas dietas com aveia (214,49mg/dL) e FADE (216,3mg/dL), enquanto para a carpa húngara as menores concentrações observadas foram nos peixes alimentados com FADE (222,54mg/dL). Quanto à composição centesimal, os valores de gordura no filé foram menores nos jundiás dos tratamentos controle (3,76%) e aveia (3,95%). A inclusão de aveia proporcionou menor deposição de gordura corporal em ambas as espécies. Conclui-se que 20% de aveia descascada ou de farelo de arroz desengordurado podem ser incluídos na dieta de juvenis de jundiá e de carpa húngara sem prejuízos para o crescimento.

The temperature of the environment is one of the most important abiotic factors affecting the life of insects. As poikilotherms, their body temperature is not constant, and they rely on various strategies to minimize the risk of thermal stress. They have been thus able to colonize a large spectrum of habitats. Mosquitoes, such as Ae. aegypti and Ae. albopictus, vector many pathogens, including dengue, chikungunya, and Zika viruses. The spread of these diseases has become a major global health concern, and it is predicted that climate change will affect the mosquitoes’ distribution, which will allow these insects to bring new pathogens to naïve populations. We synthesize here the current knowledge on the impact of temperature on the mosquito flight activity and host-seeking behavior (1); ecology and dispersion (2); as well as its potential effect on the pathogens themselves and how climate can affect the transmission of some of these pathogens (3).

Living in close association with a vertebrate host and feeding on its blood requires different types of adaptations, including behavioural adjustements. Triatomines exhibit particular traits associated with the exploitation of their habitat and food sources and these traits have been the subject of intense analysis. Many aspects of triatomine behaviour have been relatively well characterised and some attempts to exploit the behaviours have been undertaken. Baited traps based on host-associated cues, artificial refuges and light-traps are some of the tools used. Here we discuss how our knowledge of the biology of Chagas disease vectors may help us sample and detect these insects and even increase the efficiency of control measures.

Avaliaram-se o crescimento e a composição dos filés de juvenis de jundiá após 90 dias de alimentação com dietas contendo diferentes fontes protéicas. Foram utilizados 540 peixes, peso inicial=15,0±0,62g; comprimento inicial=11,98±0,35cm, distribuídos ao acaso em 18 tanques (30 peixes/tanque) com sistema de recirculação de água. Foram testadas seis dietas: 1 - farinha de carne e ossos + levedura (CL), 2 - farelo de soja + levedura (SL), 3 - farelo de soja (S), 4 - farinha de carne e ossos + farelo de soja (CS), 5 - farinha de peixe + levedura (PL) e 6 - farinha de peixe + farelo de soja (PS). Avaliaram-se: peso, comprimento total, taxa de crescimento específico, fator de condição, sobrevivência, conversão alimentar aparente, taxa de eficiência protéica e consumo diário. Também foram analisadas as composições do filé - umidade, proteína, lipídios, cinzas -, as taxas de deposição de proteína e gordura, além dos rendimentos de filé e carcaça. Maiores pesos, 111,5 e 108,6g, comprimento total, 22,6 e 21,6cm, e taxa de crescimento específico, 2,1 e 2,2%/dia, foram observados nos peixes alimentados com as dietas CS e PS. Os peixes alimentados com CS e PS também apresentaram maior deposição de proteína, 69,8 e 71,5mg/dia, e lipídios, 77,2 e 78,3mg/dia. A sobrevivência foi menor na dieta PS, 92,9%. Os maiores rendimentos de carcaça foram observados nos peixes alimentados com PS e PL, 82,9 e 82,7%, e o menor rendimento de filé ocorreu na dieta CL, 34,1%.The growth and fillet composition of jundiá juveniles after 90 days being fed with diets containing different protein sources were evaluated. Five hundred and forty fish (initial weight: 15.00±0.62g; initial length: 11.98±0.35cm) were randomly distributed in 18 tanks (30 fish/tank), in a water re-use system. Six diets were tested: 1- meat and bone meal + yeast (CL), 2- soybean meal + yeast (SL), 3- soybean meal (S), 4- meat and bone meal + soybean meal (CS), 5- fish meal + yeast (PL,) and 6- fish meal + soybean meal (PS). The following parameters were evaluated: weight, total length, specific growth rate, condition factor, survival, feed conversion ratio, protein efficiency ratio, and daily consumption. Fillet composition (moisture, protein, lipid, and ash), protein and lipid depositions ratios, carcass and fillet yields were also determined. The highest values of weight (111.5 and 108.6g), total length (22.6 and 21.6cm), and specific growth rate (2.1 and 2.2%/day), were observed in fish fed CS and PS diets. Fish fed CS and PS diets also showed the highest protein (69.8 and 71.5mg/day), and lipid depositions (77.2 and 78.3mg/day). Survival was smaller in fish fed diet PS (92.86%). The highest values of carcass yield were observed in fish fed PL and PS diets (82.9 and 82.7%), and the lower fillet yield was observed in CL diet (34.1%).

Simple eyes or ocelli coexist with compound eyes in many adult insects. The change in the morphology of the ocelli along the five larval instars of Triatoma infestans was studied by light and scanning electron microscopy. Our analysis showed that the development of the ocelli of these bugs occurs gradually along the larval life. The photoreceptor layer is present from the second-instar onwards. The cornea appears first at the imaginal stage and grows up to the 18-20th day after the last ecdysis, associated to an increase in the retinal mass. Findings are discussed in a comparative fashion and in relation to the functionality of the ocellar system in T. infestans.

The simple eyes (ocelli) of recently emerged adult Triatoma infestans exhibit a narrow elongated "pupil", surrounded by a ring of brown-reddish pigment, the "iris". This pupil does not respond to changes in the illumination, but varies in size after the imaginal ecdysis. This change corresponds, internally, with the growth of the corneal lens and the associated retina up to an age of about 20 days. This has not been previously observed in an insect. The use of this characteristic for recognising young adults of this species is suggested.

BACKGROUND: Triatomine bugs are the insect vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. These insects are known to aggregate inside shelters during daylight hours and it has been demonstrated that within shelters, the aggregation is induced by volatiles emitted from bug feces. These signals promote inter-species aggregation among most species studied, but the chemical composition is unknown. METHODOLOGY/PRINCIPAL FINDINGS: In the present work, feces from larvae of the three species were obtained and volatile compounds were identified by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). We identified five compounds, all present in feces of all of the three species: Triatoma infestans, Panstrongylus megistus and Triatoma brasiliensis. These substances were tested for attractivity and ability to recruit insects into shelters. Behaviorally active doses of the five substances were obtained for all three triatomine species. The bugs were significantly attracted to shelters baited with blends of 160 ng or 1.6 µg of each substance. CONCLUSIONS/SIGNIFICANCE: Common compounds were found in the feces of vectors of Chagas disease that actively recruited insects into shelters, which suggests that this blend of compounds could be used for the development of baits for early detection of reinfestation with triatomine bugs.

Assembling behaviour associated with mating was investigated in Triatoma infestans. The spatial distribution of both sexes was observed by video films, in the presence or absence of a copulating pair. Males aggregated around copulating pairs. Females did not exhibit this behaviour and their mean spatial density remained unaffected. Spontaneous aggregation tendency was observed in males in the absence of a copulating pair, but the temporal course significantly differed from that observed in the presence of a mating pair. Results support the existence of an aggregation signal that is released during mating, affecting the behaviour of males.

Factors affecting mating behaviour in the bug Triatoma infestans were quantitatively studied in the laboratory. Experimental conditions were established so that the probability of copulation increased with the time elapsed since the first adult meal. Copulatory attempts by males did not vary as a function of time, but rejections by females became significantly less frequent with the post feeding time. Non-receptive females displayed four types of rejection behaviour, i.e. flattening, stridulation, evasion and abdominal movements. The occurrence of stridulation performed by females in a sexual context was observed in a regular fashion and was quantified for the first time in this species.

In the second segment of the antennae of haematophagous reduviids an unusual cave-like organ is found the function os which was investigated in Triatoma infestans. the morphology of the organ makes it difficult to ascribe it to a mechno- or chemoreceptive function, but shows some characteristics shared with thermoreceptors of other animals. The electrical activity of sense cells was recorded in the presence of stimuli that evoke behavioural responses in this species, i.e. warm, CO2, lactic and butyric acids at different concentrations. The three compounds tested failed to evoke a response at all concentrations assayed. Only thermal stimulation evinced a clear modification in the electrical activity of the sense cells.Both the morphological and electrophysiological findings support a thermoreceptive finding, habitat selection and circadian synchronization.

The behavioural response of Triatoma pseudomaculata to chemical substances present in their faeces or cuticle (footprints) was analyzed. Groups of larvae were simultaneously exposed to a clean filter paper and to another paper impregnated with a chemical stimulus in a circular arena. In these choice experiments, the insects aggregated significantly around papers impregnated with dry faeces. In addition, the bugs also showed a significant aggregation response to papers impregnated with compounds derived from their cuticle that were deposited by contact on the substrate. These results indicate that chemical compounds that affect the behaviour of T. pseudomaculata are present in the faeces and in the cuticle of this species. Results are discussed in relation to chemical communication in the Triatominae, as well as to the potential use of these substances in traps or sensors for the detection of this species.

The response to intra- and interspecific faecal assembling signals was tested in Rhodnius prolixus. Papers impregnated with excrement of R. prolixus induced the aggregation of larvae of this species, but also of those of Triatoma infestans. However, faeces belonging to T. infestans were not able to assemble larvae of R. prolixus. On the other hand, there was no response of R. prolixus to putative chemical factors from their cuticle (footprints), in contrast to T. infestans. Results are discussed as related to the ecology of both species.

BACKGROUND:The developmental time of vector insects is important in population dynamics, evolutionary biology, epidemiology and in their responses to global climatic change. In the triatomines (Triatominae, Reduviidae), vectors of Chagas disease, evolutionary ecology concepts, which may allow for a better understanding of their biology, have not been applied. Despite delay in the molting in some individuals observed in triatomines, no effort was made to explain this variability. METHODOLOGY:We applied four methods: (1) an e-mail survey sent to 30 researchers with experience in triatomines, (2) a statistical description of the developmental time of eleven triatomine species, (3) a relationship between development time pattern and climatic inter-annual variability, (4) a mathematical optimization model of evolution of developmental delay (diapause). PRINCIPAL FINDINGS:85.6% of responses informed on prolonged developmental times in 5(th) instar nymphs, with 20 species identified with remarkable developmental delays. The developmental time analysis showed some degree of bi-modal pattern of the development time of the 5(th) instars in nine out of eleven species but no trend between development time pattern and climatic inter-annual variability was observed. Our optimization model predicts that the developmental delays could be due to an adaptive risk-spreading diapause strategy, only if survival throughout the diapause period and the probability of random occurrence of "bad" environmental conditions are sufficiently high. CONCLUSIONS/SIGNIFICANCE:Developmental delay may not be a simple non-adaptive phenotypic plasticity in development time, and could be a form of adaptive diapause associated to a physiological mechanism related to the postponement of the initiation of reproduction, as an adaptation to environmental stochasticity through a spreading of risk (bet-hedging) strategy. We identify a series of parameters that can be measured in the field and laboratory to test this hypothesis. The importance of these findings is discussed in terms of global climatic change and epidemiological consequences.

BackgroundIt is known that some blood-sucking insects have the ability to reach vessels under the host skin with their mouthparts to feed blood from inside them. However, the process by which they locate these vessels remains largely unknown. Less than 5% of the skin is occupied by blood vessels and thus, it is not likely that insects rely on a "random search strategy", since it would increase the probability of being killed by their hosts. Indeed, heterogeneities along the skin surface might offer exploitable information for guiding insect's bites.Methodology/principal findingsWe tested whether the bug Rhodnius prolixus can evaluate temperature discontinuities along the body surface in order to locate vessels before piercing the host skin. When placed over a rabbit ear, the bug's first bites were mostly directed towards the main vessels. When insects were confronted to artificial linear heat sources presenting a temperature gradient against the background, most bites were directly addressed to the warmer linear source, notwithstanding the temperature of both, the source and the background. Finally, tests performed using uni- and bilaterally antennectomized insects revealed that the bilateral integration of thermal inputs from both antennae is necessary for precisely directing bites.Conclusions/significanceR. prolixus may be able to exploit the temperature differences observed over the skin surface to locate blood vessles. Bugs bite the warmest targets regardless of the target/background temperatures, suggesting that they do not bite choosing a preferred temperature, but select temperature discontinuities along the skin. This strategy seems to be an efficient one for finding blood vessels within a wide temperature range, allowing finding them on different hosts, as well as on different areas of the host body. Our study also adds new insight about the use of antennal thermal inputs by blood sucking bugs.