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Aggregation is one of the most remarkable behaviours in the animal kingdom—a process that is usually governed by pheromones. Triatomines are blood-sucking bugs that act as vectors of Trypanosoma cruzi, the etiological agent of Chagas disease in mammals, including humans. Triatomines usually gather in roosting refuges by using aggregation pheromones of unknown chemical structure. In terms of vector control, one option to reduce triatomine–human contact is via capturing the insects into traps baited with lures based on such aggregation pheromones. As a first step towards this aim, we elucidated the aggregation pheromone in the triatomine Triatoma pallidipennis, using T. cruzi-infected and non-infected bugs. We used different extraction techniques and gas chromatography coupled to mass spectrometry for the identification. Also, two different bioassays were implemented for evaluating the attractant and arrestant activity of the pheromone. We found that T. pallidipennis produced short-chain aldehydes as attractants, and nitrogen-derived compounds as arrestants. We detected differences in the production and perception of these compounds according to whether animals were infected or not. These findings show that T. cruzi may influence triatomine chemical ecology and are promising tools for triatomine control.

Collaboration is a fundamental aspect of scientific research and innovation. Fair collaborations between scientists from different identities or positions of power (e.g., Global North and Global South scientists) could have a great impact on scientific knowledge and exchange. However, there are existing limitations to the potential of Global South scientists to collaborate fairly. Here we assess the impact and geographic distribution of international collaborations for PhD students in biological sciences in four Global South countries (two from Africa: Algeria and Morocco, and two from the Americas: Colombia and Mexico), where students typically have low English proficiency. We show that overall international collaboration, particularly with the Global North, increased the probability of publishing in a journal with an impact factor and achieved more citations. Most international collaborators were affiliated with French-speaking countries for Algerian and Moroccan students and Spanish and English-speaking countries for Colombian and Mexican universities, suggesting that language and geopolitical history might play a role in shaping the selection of international collaborators. While the results highlight the benefit of international collaboration for researchers in the Global South, we discuss that the current metrics of scientific success could maintain the dependence of Global South scientists on the Global North.

The introduction of species is a leading cause of biodiversity loss and habitat alteration. Several species have invaded Mexican freshwater ecosystems, adversely affecting native fishes. Specifically, in the Amacuzac River of the Balsas Basin (Central Mexico), at least four non-native cichlids have been recorded: tilapia Oreochromis sp., convict cichlid Amatitlania nigrofasciata, spotcheek cichlid Thorichthys maculipinnis, and green terror Andinoacara rivulatus. These species co-occur with the Mexican mojarra Amphilophus istlanus, the only native cichlid in the Basin. Invasive cichlids compete for resources such as shelter and food, and prey on offspring of the Mexican mojarra. In the presence of invasive cichlids, the costs and risks of foraging and finding available shelter increase for the native cichlid. Predation pressure from invasive cichlid fishes on the Mexican mojarra increases the time invested by parents in caring for offspring and their stress levels, potentially contributing to Mexican mojarra population declines. Here, we gathered the best evidence available to discuss some mechanisms and consequences of such co-occurrences in relation to reproductive behaviors, parental care, competition for resources, and dominance hierarchy, and how the four invasive cichlids have negatively affected the Mexican mojarra.

Land use/land cover change (LULCC) is a major threat that affects the viability of insect populations worldwide yet our estimates of such effects are usually poor. We analysed how LULCC affected the distribution of 49 species of dragonflies and damselflies in the south-central zone in Mexico during the period 2006-2012. For this, we mapped the potential species richness using ecological niche models in order to analyse predicted future changes and determined the effect of LULCC on the current and future habitats of Odonata. We also estimated current incidence of deforestation and projected its effect to 2050 using the Dinamica-EGO program. Having predicted the level of deforestation in the year 2050, we then compared current vs. expected species richness and the factors that determine it. First, roads and urban areas turned out to be the most important drivers of LULCC in our analysis. Second, deterioration occurred at all sites, but species richness remained high despite considerable habitat fragmentation. Third, there is likely to be a high species turnover rate (i.e. a high species richness, but composed of different species) even in areas where there are significant changes in the vegetation. Our work illustrates both a resilience of Odonata to LULCC and provides a useful method for measuring the effects of LULCC on insects.

Ectothermic animals can raise their body temperature under varying circumstances. Two such situations occur during sexual activity (as metabolic rate rises during copulatory movements) and during infection (to control pathogens more effectively). We have investigated these two situations using Tenebrio molitor males. We recorded the copulatory courtship behavior of sick (= infected with Metharizium robertsii fungus) vs healthy males and its link with body temperature. We predicted a positive relation between copulatory courtship (measured as antennal and leg contact behavior) and body temperature, especially in sick males. We found that the intensity of contacts correlated with increased body temperature in sick males. Previous studies in this species indicated that partner females laid fewer eggs after mating with sick males above a certain male body temperature threshold. Thus, our present findings suggest that females may detect male infection via intensity of antennal-mediated courtship, body temperature or their combination. If this is the case, females may assess male cues directly related to health status such as body temperature.

Abstract Background Relatively little is known about how pathogens transmitted by vector insects are affected by changing temperatures analogous to those occurring in the present global warming scenario. One expectation is that, like their ectothermic vectors, an increase in temperature could reduce their fitness. Here, we have investigated the effect of high temperatures on the abundance of Trypanosoma cruzi parasites during infection in the vector Triatoma pallidipennis. Methods We exposed T. pallidipennis nymphs to two strains (Morelos and Chilpancingo) of T. cruzi. Once infected, the fifth-instar bugs were distributed among three different temperature groups, i.e. 20, 30, and 34 °C, and the resulting parasites were counted when the bugs reached adulthood. Results The number of parasites increased linearly with time at 20 °C and, to a lesser extent, at 30 °C, especially in the Chilpancingo compared to the Morelos strain. Conversely, at 34 °C, the number of parasites of both strains decreased significantly compared to the other two temperatures. Conclusions These results suggest negative effects on the abundance of T. cruzi in T. pallidipennis at high temperatures. This is the first evidence of the effect of high temperatures on a pathogenic agent transmitted by an insect vector in the context of global warming. Further tests should be done to determine whether this pattern occurs with other triatomine species and T. cruzi strains. Graphical abstract

Abstract Postcopulatory sexual selection has shaped the ornaments used during copulatory courtship. However, we know relatively little about whether these courtship ornaments are costly to produce or whether they provide indirect benefits to females. We used the mealworm beetle, Tenebrio molitor, to explore this. We challenged males using an entomopathogenic fungus and compared their courtship (frequency of leg and antennal contacts to the female), copulation duration, number of eggs laid, and hatching rate against control males. Infected males copulated for longer yet they reduced their leg and antennal contacts compared to control males. However, there was no obvious relation between infection, copulation duration, and courtship with egg production and hatching success. In general, our results indicate that the ornaments used during postcopulatory courtship are condition‐dependent. Moreover, such condition dependence cannot be linked to male fitness.

Cities function as ecological systems composed of a geosphere, a biosphere and an anthroposphere, interacting with each other and generating various selection pressures on urban organisms. Odonates (damselflies and dragonflies) are frequent inhabitants of urban areas, showing no clear or unique responses to urbanization. Thus, we defined an urbanization gradient using a habitat integrity index (HII) calculated for 19 sites in central Mexico, and investigated: a) changes in species richness and abundance along the urbanization gradient; and, b) the relationship between presence of waste of anthropic origin, chemical conditions of water, macrophyte cover, and odonate species richness, abundance and community composition. We analyzed the data for the whole odonate community, as well as for dragonfly and damselfly communities separately in each site. We found higher damselfly species richness and abundance in sites with low urbanization than in sites with high urbanization, and no differences in dragonfly communities along the gradient. We found a positive relationship between dragonfly species richness and abundance and waste percentage and macrophyte cover, and a negative relationship with dissolved solids in water. Our results indicated that odonate communities were fairly tolerant to urbanization and dragonflies were less affected than damselflies. However, we suggest that during design and restructuring of cities, the care and conservation of water bodies and all the life forms that inhabit there, be considered.

Aim: Insects are one of the least studied taxa, with most species lacking basic ecological and biogeographical information. This problem is particularly acute in the tropics, where low sampling effort hampers accurate estimates of species richness at scale and potentially confounds efforts to identify the drivers of biogeographical gradients. Here, we evaluate the quality of the data on the distribution and diversity of odonate species in the Neotropics, while also examining the influence of sampling completeness on climate–richness relationships using a comprehensive database of odonates. Location: The Neotropics. Taxon: Odonata. Methods: Using 56,535 records collected from 1970 to 2021, we assess whether climate–species richness models vary under different scenarios of survey completeness. Results: Our survey compilation revealed that most Neotropical diversity of Odonata likely remains unknown. Only 1% of the one‐degree cells covering the Neotropics held reliable information on odonate species richness, with particularly severe gaps in the Caribbean, Central America, northeastern Brazil and northern Chile. Temperature, precipitation and potential evapotranspiration exert consistent effects on Odonata richness across the entire Neotropics, regardless the level of survey completeness. Whereas seasonality‐related variables are less important predictors of species richness at the biogeographical scale. Main Conclusions: By highlighting areas where inventories are more reliable and identifying regions that require increased data collection efforts and mobilization, our assessment offers a roadmap for improving the reliability of odonate inventories in the Neotropics. Furthermore, our findings underscore the importance of accounting for varying levels of survey completeness in macroecological models to reveal robust climate–species richness relationships. Simultaneously, they highlight strong climatic predictors of species richness, irrespective of survey effort intensity. These predictors provide a solid foundation for modelling and predicting odonate species richness in the Neotropics. [ABSTRACT FROM AUTHOR]

Triatomines are haematophagous insects, some species are vectors of Trypanosoma cruzi, the aetiological agent of Chagas disease. The main strategy for interrupting T. cruzi transmission is to avoid contact of the vector populations with humans. Volatiles from commercial essential oils are excellent candidates to serve as repellents of kissing bugs. We used an exposure device to assess the repellence effect of eight commercial essential oils on Triatoma pallidipennis. The most effective oils were blended and evaluated against T. infestans, T. pallidipennis and Rhodnius prolixus. The blend was also evaluated on parasitised T. pallidipennis. Data were compared with the commercial repellent NN‐diethyl‐3‐methylbenzamide. We recorded the time the insects spent in the proximity of the host and determined if any of the evaluated oils served as kissing bug repellent. We found commercial essential oils and a blend that significantly reduced the time spent in the proximity of the host. The blend was effective for use by human males and females, repelling infected and non‐infected insects. The study of essential oils as repellents of blood‐sucking disease‐vector insects could shed light on the development of new control strategies. [ABSTRACT FROM AUTHOR]

Environmental change (i.e., urbanization) impacts species in contrasting ways, with some species experiencing benefits given their way of life (i.e., blood-sucking insects). How these species respond to such change is not well understood and for species involved in human diseases, this “how” question is particularly important. Most Triatominae bug species inhabit tropical and subtropical forests where their vertebrate hosts’ temporal abundance depends on climate seasonality. However, in human encroached landscapes, triatomines can benefit from resource stability which may lead to adaptive phenotypic change to track novel hosts. We tested for an association between different landscapes and morpho-functional traits linked to sensory, motion, and feeding functions in Triatoma dimidiata and compared fecundity (i.e., number of eggs) in each landscape as a proxy of fitness. Using geometric and traditional morphometric tools, we predicted a morphological simplification in bugs inhabiting urbanized areas. While wing morphology or proboscis were not influenced by landscape class, the opposite occurred for thorax morphology and number of sensilla. Wing and thorax morphology did not covary under modified landscape scenarios, yet we detected a morpho-functional convergence for thorax size and antennal phenotype in both sexes, with a simplification trend, from nature to urban settings. Given no fecundity differences across landscapes, there is no potential reproductive costs. Moreover, the convergence of thorax size and antennal phenotype suggests differences in flight/locomotion performance and host/environment perception, as a possible adaptive response to relaxed selective pressures of the bug’s native habitat. These results imply that T. dimidiata could be adapting to urbanized areas.

Abstract Background Theory predicts that parasites can affect and thus drive their hosts’ niche. Testing this prediction is key, especially for vector-borne diseases including Chagas disease. Here, we examined the niche use of seven triatomine species that occur in Mexico, based on whether they are infected or not with Trypanosoma cruzi, the vectors and causative parasites of Chagas disease, respectively. Presence data for seven species of triatomines (Triatoma barberi, T. dimidiata, T. longipennis, T. mazzottii, T. pallidipennis, T. phyllosoma and T. picturata) were used and divided into populations infected and not infected by T. cruzi. Species distribution models were generated with Maxent 3.3.3k. Using distribution models, niche analysis tests of amplitude and distance to centroids were carried out for infected vs non-infected populations within species. Results Infected populations of bugs of six out of the seven triatomine species showed a reduced ecological space compared to non-infected populations. In all but one case (T. pallidipennis), the niche used by infected populations was close to the niche centroid of its insect host. Conclusions Trypanosoma cruzi may have selected for a restricted niche amplitude in triatomines, although we are unaware of the underlying reasons. Possibly the fact that T. cruzi infection bears a fitness cost for triatomines is what narrows the niche breadth of the insects. Our results imply that Chagas control programmes should consider whether bugs are infected in models of triatomine distribution.

Abstract Background Little is known about how human disease vectors will modify their life history patterns and survival capacity as a result of climate change. One case is that of Chagas disease, which has triatomine bugs and Trypanosoma cruzi as vectors and parasite, respectively. This work aimed to determine: (i) the activity of the prophenoloxidase system (prophenoloxidase and phenoloxidase activity, two indicators of immune ability) in three intestine regions (anterior midgut, posterior midgutand rectum) of the triatomine bug Meccus pallidipennis under three temperature conditions (20 °C, 30 °C and 34 °C) against two T. cruzi strains [ITRI/MX/14/CHIL (Chilpancingo) and ITRI/MX/12/MOR (Morelos)], and (ii) whether vector survival varies under these three temperatures after infection by these T. cruzi strains. Results Our results indicate that prophenoloxidase activity was lower at higher temperatures, that the level of prophenoloxidase activity elicited by each strain was different (higher in Chilpancingo than in Morelos strains), and that prophenoloxidase activity was more intense in the anterior midgut than in the posterior midgut or rectum. Survival rates were lower in insects maintained at higher temperatures and infected by Chilpancingo strains. Conclusions These results indicate that climate change could lead to lower prophenoloxidase activity and survival rates in triatomines when infected with different T. cruzi strains, which could reduce the vector capacity of M. pallidipennis.

Ecosystem services relies on several insects that provide fundamental functions. Despite the quality of these ecosystem services depends on insect diversity, abundance and biomass, little is known about the effects that individual body condition has over such services. One prediction is that starving or sick animals may provide a reduced service. Dung beetles bury dung in forests and cattle farms, contributing to soil fertilization and reduction of greenhouse gas emissions from livestock. However, some species are highly sensitive to habitat disturbance and this leads to important losses of ecosystem services in disturbed areas. Here we experimentally tested the effect of diet quality and parasite pressure impact on dung removal rate using three species of dung beetles from contrasting habitats. We exposed wild beetles to an immune challenge combined with experimental diets that varied in protein content. We predicted that dung removal would be better carried out by healthy and well-fed individuals. However, if a species incurs in compensatory feeding or terminal investment in reproduction, ill individuals will still exhibit intense dung removal and reproductive activity but with a physiological cost. For Euoniticellus intermedius beetles, the immune challenge reduced dung removal rates, and this was because the challenge reduced the weight, although not the number of built brood masses. This suggests that implanted individuals made an intense reproductive effort. Therefore, a strategy of terminal investment in reproduction might be occurring. In the same species, couples fed low-protein diets increased dung removal rates compared to control-fed animals, probably as a compensatory feeding strategy that increased energetic condition. Conversely, Onthophagus incensus and O. rhinolophus beetles did not change dung removal rates despite suffering changes in energetic condition resulting from treatment. This is the first evidence that ecosystem services provided by dung beetles depend on individual health and nutritional status that drive reproductive and feeding behavior. Understanding the environmental factors that affect individual physiology and behavior is fundamental to guarantee conditions not only for the survival of key species but also for the maintenance of ecosystem services.

Males of many insects deliver ejaculates with nutritious substances to females in the form of a spermatophore. Different factors can affect spermatophore quality. We manipulated males’ diet and health to determine the balance of macronutrients deposited in the spermatophores of Tenebrio molitor beetles. For diet, we varied the concentration of proteins and carbohydrates, while for health status we used a fungal infection. Males with different condition copulated with unmanipulated females, and spermatophores were extracted to measure the amount of proteins, lipids and carbohydrates. Diet and infection had an effect on the quality of the spermatophore. Diets with high protein and low carbohydrate contents produced spermatophores with higher protein, carbohydrate, and lipid contents. In contrast, diets with little protein and high in carbohydrates led to low quality spermatophores. Infected males produced spermatophores with the highest amount of all three macronutrients. In general, spermatophore content was carbohydrates>proteins>=lipids. The fact that sick males produced richer spermatophores can be explained as a terminal investment strategy. The large investment of carbohydrates may be related to the preparation of spermatozoa in males, and eggs in females.

Abstract Background Triatomine insects are vectors of Trypanosoma cruzi, the causal agent of Chagas disease. The insect-parasite interaction has been studied in relation to the transmission and prevalence of this disease. For most triatomines, however, several crucial aspects of the insect immune response are still unknown. For example, only for Rhodnius prolixus and Triatoma infestans has the activity of phenoloxidase (PO) and its zymogen prophenoloxidase (proPO) been reported in relation to the hemolymph and anterior midgut (AM). The aim of this study was to gain insight into the immune response to T. cruzi infection of an important triatomine in Mexico, Meccus pallidipennis. Methods Parasites were quantified in the rectal contents of infected M. pallidipennis groups. We examined some key factors in disease transmission, including the systemic (hemolymph) and local (gut) immune response. Results Parasites were present in the rectal contents at 4 days post-infection (pi) and reached their maximum density on day 7 pi. At 7 and 9 days pi mainly metacyclic trypomastigotes occurred. Compared to the control, the infected insects exhibited diminished PO activity in the hemolymph on days 9, 16 and 20 pi, and in the AM only on day 9. Additionally, infected insects displayed lower proPO activity in the hemolymph on day 1, but greater activity in the AM on day 28. Conclusions The parasite strain originating from M. pallidipennis rapidly colonized the rectum of nymphs of this triatomine and developed high numbers of metacyclic trypomastigotes. Neither the changes of concentrations of PO and proPO in the hemolymph nor in the AM correlated with the changes in the population of T. cruzi.

Abstract Sexual conflict over mating rate is both pervasive and evolutionarily costly. For females, the lifetime reproductive fitness costs that arise through interactions with potential mates will be influenced by the frequency of such interactions, and the fitness cost of each interaction. Both of these factors are likely to be influenced by variation in operational sex ratio (OSR) and population density. Variation in OSR‐ and density‐dependent male alternative reproductive tactics (ARTs) may be particularly important if the fitness costs that females experience vary with the reproductive tactics that males express. Using a simple model, we consider several examples of OSR‐ and/or density‐dependent variation in male ARTs and the frequency of male–female interactions, and find that variation in the expression of male ARTs has the potential to augment or diminish the costs of frequent male interactions for females. Accurately documenting variation in the expression of male ARTs and associated female fitness costs will benefit future work in this area.

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