Distribution and natural infection status of synantrophic triatomines (Hemiptera: Reduviidae), vectors of Trypanosoma cruzi, reveals new epidemiological scenarios for chagas disease in the Highlands of Colombia.

INTRODUCTION: Updating the distribution and natural infection status of triatomine bugs is critical for planning, prioritizing, and implementing strategies to control Chagas disease (CD), especially after vector reduction programs. After carrying out a control program, the Department of Boyaca contains the highest number of Colombian municipalities certified by PAHO to be free of intradomiciliary transmission of Trypanosoma cruzi by Rhodnius prolixus. The present work describes the spatial distribution, natural infection (NI), and molecular characterization of T. cruzi in synanthropic triatomines from the Department of Boyaca in 2017 and 2018. MATERIALS AND METHODS: An entomological survey was conducted in 52 municipalities in Boyaca known to have had previous infestations of triatomine bugs. Insects were collected through active searches carried out by technical personnel from the Secretary of Health and community members using Triatomine Collection Stations (PITs-acronym in Spanish). For evaluation of natural infection, triatomines were identified morphologically and grouped in pools of one to five individuals of the same species collected in the same household. DNA derived from the feces of each pool of insects was analyzed by PCR for the presence of T. cruzi using primers flanking the satellite DNA of the parasite. SL-IR primers were used to differentiate TCI from the other DTUs and to identify different genotypes. The distribution of the collected triatomines was analyzed to determine any vector hotspots using spatial recreation. RESULTS: A total of 670 triatomine bugs was collected, belonging to five species: Triatoma dimidiata (73.2%), Triatoma venosa (16.7%), Panstrongylus geniculatus (5.7%), Rhodnius prolixus (4.4%), and Panstrongylus rufotuberculatus (0.4%), from 29 of the 52 municipalities. In total, 71.6% of the bugs were collected within houses (intradomiciliary) and the rest around the houses (peridomiciliary). Triatoma dimidiata was the most widely distributed species and had the highest natural infection index (37.8%), followed by T. venosa and P. geniculatus. TcI was the only DTU found, with the TcI Dom genotype identified in 80% of positive samples and TcI sylvatic in the other insects. Spatial analysis showed clusters of T. dimidiata and T. venosa in the northeast and southwest regions of Boyaca. CONCLUSIONS: After some municipalities were certified free of natural transmission within houses (intradomiciliary transmission) of T. cruzi by R. prolixus, T. dimidiata has become the most prevalent vector present, and represents a significant risk of resurgent CD transmission. However, T. venosa, P. geniculatus, and P. rufotuberculatus also contribute to the increased risk of transmission. The presence of residual R. prolixus may undo the successes achieved through vector elimination programs. The molecular and spatial analysis used here allows us to identify areas with an ongoing threat of parasite transmission and improve entomological surveillance strategies.

Behavioral parameters of six populations of Meccus phyllosomus longipennis (Heteroptera: Reduviidae) from areas with high and low prevalences of Trypanosoma cruzi human infection.

Three behaviors of epidemiological importance, namely feeding latency, feeding duration and defecation latency, for six populations of Meccus phyllosomus longipennis (Usinger) from areas of central, western and north-central Mexico with high (HP) and low (LP) prevalence of Trypanosoma cruzi (Chagas) human infection were evaluated in this study. The median feeding latency (the time taken to begin feeding) was highly variable between instars. Within-instar comparisons showed that at least 65% of the LP populations (N3 to adult) started to feed significantly (P < 0.05) later than the HP population, with N1 showing no difference, and N2 from LP populations feeding sooner than those from HP populations. The six populations had similar median feeding durations within instars. A higher (P < 0.05) percentage of the instars from HP populations defecated faster than the respective instars from the three LP populations. Approximately 25% of the young nymphs (N1 to N3) and females in the HP populations defecated < 2 min postfeeding, compared with 4%-6% of the young nymphs and 1.3%-3% of females in the LP populations. Moreover, 17.7%-38.8% of the older nymphs (N4 to N5) in the HP populations and 6.8%-13.4% in the LP populations defecated during or immediately after feeding. Our results indicate that the HP populations have a greater potential than the LP populations to transmit T. cruzi infections, which may underlie the differences in the prevalence of T. cruzi infection in some areas where M. p. longipennis is currently distributed.

Crouching Tiger, Hidden Protein: Searching for Insecticidal Toxins in Venom of the Red Tiger Assassin Bug (Havinthus rufovarius).

Assassin bugs are venomous insects that prey on other arthropods. Their venom has lethal, paralytic, and liquifying effects when injected into prey, but the toxins responsible for these effects are unknown. To identify bioactive assassin bug toxins, venom was harvested from the red tiger assassin bug (Havinthus rufovarius), an Australian species whose venom has not previously been characterised. The venom was fractionated using reversed-phase high-performance liquid chromatography, and four fractions were found to cause paralysis and death when injected into sheep blowflies (Lucilia cuprina). The amino acid sequences of the major proteins in two of these fractions were elucidated by comparing liquid chromatography/tandem mass spectrometry data with a translated venom-gland transcriptome. The most abundant components were identified as a solitary 12.8 kDa CUB (complement C1r/C1s, Uegf, Bmp1) domain protein and a 9.5 kDa cystatin. CUB domains are present in multidomain proteins with diverse functions, including insect proteases. Although solitary CUB domain proteins have been reported to exist in other heteropteran venoms, such as that of the bee killer assassin bug Pristhesancus plagipennis, their function is unknown, and they have not previously been reported as lethal or paralysis-inducing. Cystatins occur in the venoms of spiders and snakes, but again with an unknown function. Reduction and alkylation experiments revealed that the H. rufovarius venom cystatin featured five cysteine residues, one of which featured a free sulfhydryl group. These data suggest that solitary CUB domain proteins and/or cystatins may contribute to the insecticidal activity of assassin bug venom.

Bioefficacy of Rhynocoris longifrons (Stål) (Heteroptera: Reduviidae) against multiple cotton pests under screen house and field conditions.

Rhynocoris longifrons (Hemiptera: Reduviidae) is a generalist predator of many cotton insect pests. The hiding behaviour of this predator, which is one of the key factors of predation success, was investigated under screen house conditions. Moreover, we evaluated its biocontrol potential against Aphis gossypii (Hemiptera: Aphididae), Dysdercus cingulatus (Hemiptera: Pyrrhocoridae), Phenacoccus solenopsis (Hemiptera: Pseudococcidae), and Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) under screen house and field conditions. Results showed that R. longifrons life stages preferred to hide under small pebbles in the screen house tests. All the R. longifrons life stages showed a biocontrol potential against the four insect pests under screen house conditions. However, their biocontrol potential had not varied in relation to day and night hours. Augmentative releases of R. longifrons were carried out for two seasons such as South-west monsoon, 2011 and post-monsoon, 2012. The augmentative release of R. longifrons reduced significantly insect pests on cotton. In fact, the release of this predator in cotton fields was capable to reduce the population of H. armigera (50%), P. solenopsis (28%), D. cingulatus (18.8%), and A. gossypii (11.8%) during the rain fed condition (south-west monsoon season). During irrigated condition (post-monsoon season), populations of D. cingulatus were reduced by 26%, than P. solenopsis (20.6%), and A. gossypii (16.8%). Except ants, no negative impact was reported on other natural enemies present in the cotton field. Significantly higher crop yield and cost benefit ratio was observed in the predator release plots indicating that R. longifrons can be used in an integrated pest management program for multiple cotton pests.

Bite Caused by the Assassin Bug Zelus Fabricius, 1803 (Hemiptera; Heteroptera: Reduviidae) in a Human.

A 47-y-old man was bitten by a reduviid bug from the Zelus Fabricius, 1803 genus, which was hidden inside a rubber-coated boot. The bite caused immediate and sharp pain, followed by local edema and constant pruritus for 15 d. Pain and fever within the first 24 h were managed with analgesics as needed, and resolution was complete and without sequelae after 21 d.

Invasion of the assassin bug Agriosphodrus dohrni (Hemiptera: Reduviidae) to Japan: Source estimation inferred from mitochondrial and nuclear gene sequences.

A large-sized assassin bug Agriosphodrus dohrni (Signoret), has been recorded from India, Vietnam, China and Japan. It is one of the potential biological control agents against some important agricultural and forest pests. This species is speculated to have invaded Japan from its native range in China about 60 years ago. We used three mitochondrial gene fragments (COI, Cytb, and ND5) and one nuclear gene fragment (EF-1α) to clarify the invasion history of A. dohrni and assess the effects of geographic events and associated ecological adaptation on the distribution pattern. The native populations of A. dohrni in China are divided into three distinct groups, which might be molded by the Early Pleistocene glaciation event and diverged during the Calabrian Stage. However, consistent with the hypothesis of a recent invasion, extremely low level of genetic variation was detected in the Japanese populations, with only two haplotypes for the combined mitochondrial genes. Both the splits network and the ML/BI phylogenetic trees revealed that haplotypes of Japan were more closely-related to those from eastern China. Therefore, we postulate that there has been only one introduction event, probably from somewhere around the Nanjing (NJ) and Lin'an (LA) populations of eastern China.

The assassin bug Pristhesancus plagipennis produces two distinct venoms in separate gland lumens.

The assassin bug venom system plays diverse roles in prey capture, defence and extra-oral digestion, but it is poorly characterised, partly due to its anatomical complexity. Here we demonstrate that this complexity results from numerous adaptations that enable assassin bugs to modulate the composition of their venom in a context-dependent manner. Gland reconstructions from multimodal imaging reveal three distinct venom gland lumens: the anterior main gland (AMG); posterior main gland (PMG); and accessory gland (AG). Transcriptomic and proteomic experiments demonstrate that the AMG and PMG produce and accumulate distinct sets of venom proteins and peptides. PMG venom, which can be elicited by electrostimulation, potently paralyses and kills prey insects. In contrast, AMG venom elicited by harassment does not paralyse prey insects, suggesting a defensive role. Our data suggest that assassin bugs produce offensive and defensive venoms in anatomically distinct glands, an evolutionary adaptation that, to our knowledge, has not been described for any other venomous animal.

Ecological and physiological thermal niches to understand distribution of Chagas disease vectors in Latin America.

In order to assess how triatomines (Hemiptera, Reduviidae), Chagas disease vectors, are distributed through Latin America, we analysed the relationship between the ecological niche and the limits of the physiological thermal niche in seven species of triatomines. We combined two methodological approaches: species distribution models, and physiological tolerances. First, we modelled the ecological niche and identified the most important abiotic factor for their distribution. Then, thermal tolerance limits were analysed by measuring maximum and minimum critical temperatures, upper lethal temperature, and 'chill-coma recovery time'. Finally, we used phylogenetic independent contrasts to analyse the link between limiting factors and the thermal tolerance range for the assessment of ecological hypotheses that provide a different outlook for the geo-epidemiology of Chagas disease. In triatomines, thermo-tolerance range increases with increasing latitude mainly due to better cold tolerances, suggesting an effect of thermal selection. In turn, physiological analyses show that species reaching southernmost areas have a higher thermo-tolerance than those with tropical distributions, denoting that thermo-tolerance is limiting the southern distribution. Understanding the latitudinal range along its physiological limits of disease vectors may prove useful to test ecological hypotheses and improve strategies and efficiency of vector control at the local and regional levels.

Impact of climate change on vector transmission of Trypanosoma cruzi (Chagas, 1909) in North America.

Climate change can influence the geographical range of the ecological niche of pathogens by altering biotic interactions with vectors and reservoirs. The distributions of 20 epidemiologically important triatomine species in North America were modelled, comparing the genetic algorithm for rule-set prediction (GARP) and maximum entropy (MaxEnt), with or without topographical variables. Potential shifts in transmission niche for Trypanosoma cruzi (Trypanosomatida: Trypanosomatidae) (Chagas, 1909) were analysed for 2050 and 2070 in Representative Concentration Pathway (RCP) 4.5 and RCP 8.5. There were no significant quantitative range differences between the GARP and MaxEnt models, but GARP models best represented known distributions for most species [partial-receiver operating characteristic (ROC) > 1]; elevation was an important variable contributing to the ecological niche model (ENM). There was little difference between niche breadth projections for RCP 4.5 and RCP 8.5; the majority of species shifted significantly in both periods. Those species with the greatest current distribution range are expected to have the greatest shifts. Positional changes in the centroid, although reduced for most species, were associated with latitude. A significant increase or decrease in mean niche elevation is expected principally for Neotropical 1 species. The impact of climate change will be specific to each species, its biogeographical region and its latitude. North American triatomines with the greatest current distribution ranges (Nearctic 2 and Nearctic/Neotropical) will have the greatest future distribution shifts. Significant shifts (increases or decreases) in mean elevation over time are projected principally for the Neotropical species with the broadest current distributions. Changes in the vector exposure threat to the human population were significant for both future periods, with a 1.48% increase for urban populations and a 1.76% increase for rural populations in 2050.

Functional Response of the Predators Alloeocranum biannulipes (Hemiptera: Reduviidae) and Teretrius nigrescens (Coleoptera: Histeridae) Feeding on Dinoderus porcellus (Coleoptera: Bostrichidae) Infesting Yam Chips.

The functional response and some predation parameters of the predators Alloeocranum biannulipes Montrouzier & Signoret (Hemiptera: Reduviidea) and Teretrius nigrescens Lewis (Coleoptera: Histeridae) were evaluated at five different densities of larvae and pupae of Dinoderus porcellus Lesne (Coleoptera: Bostrichidae) with the aim to understand their roles in the biological control of this major pest of stored yam chips. Experiments were performed in petri dishes at 25 ± 1 °C, 60 ± 10% RH, and a photoperiod of 12:12 (L:D) h in a controlled temperature room. Both predators showed Type II of functional response with respect to larvae, determined by a logistic regression model. However, T. nigrescens significantly killed more larvae of D. porcellus compared with A. biannulipes. This behavior, however, changed to a linear functional response (Type I), when pupae of D. porcellus were offered to both predators, possibly because of their immobility. In addition, there was no significant difference between T. nigrescens and A. biannulipes in terms of the killed pupae. Parameters of the Holling disc equation for both predators were estimated. Estimated handling time on larvae of D. porcellus for T. nigrescens and A. biannulipes was 0.254 and 0.677 h and the rate of searching efficiency was 0.289 and 0.348 h-1, respectively. Results indicated that T. nigrescens was a more suitable candidate for augmentative release for D. porcellus control than A. biannulipes. However, semifield studies are required to draw firm conclusions.

Transmission Capacity of Trypanosoma cruzi (Trypanosomatida: Trypanosomatidae) by Three Subspecies of Meccus phyllosomus (Heteroptera: Reduviidae) and Their Hybrids.

Three behaviors of epidemiological importance: the time lapse for the onset of feeding, actual feeding, and defecation time for Meccus phyllosomus pallidipennis (Stål), Meccus phyllosomus longipennis (Usinger), Meccus phyllosomus picturatus (Usinger), and their laboratory hybrids were evaluated in this study. The mean time lapse for the beginning of feeding was between 0.5 and 8.3 min considering all instars in each cohort, with highly significant differences only among fifth-instar nymphs, females, and males of M. p. pallidipennis and M. p. longipennis relative to the hybrid cohorts. Four hybrid (LoPa [M. p. longipennis and M. p. pallidipennis] and LoPi [M. p. longipennis and M. p. picturatus] and their reciprocal experimental crosses) cohorts had similar mean feeding times to one of the parental subspecies, but longer than the other one. The remaining hybrid cohort (PaPi [M. p. pallidipennis and M. p. picturatus]) had longer feeding times than both of its parental subspecies. The specimens of the LoPa and LoPi hybrid cohorts defecated faster than the respective instars of the three parental cohorts. With exception of first- and fifth-instar nymphs, PaPi cohorts defecated faster than the remaining seven cohorts. More than 60% of defecation events occurred during feeding in the six hybrid cohorts. Our results indicate that hybrid cohorts have more potential to acquire infection and transmit Trypanosoma cruzi Chagas than their parental cohorts.

Origin, evolution and function of the hemipteran perimicrovillar membrane with emphasis on Reduviidae that transmit Chagas disease.

The peritrophic matrix is a chitin-protein structure that envelops the food bolus in the midgut of the majority of insects, but is absent in some groups which have, instead, an unusual extra-cellular lipoprotein membrane named the perimicrovillar membrane. The presence of the perimicrovillar membrane (PMM) allows these insects to exploit restricted ecological niches during all life stages. It is found only in some members of the superorder Paraneoptera and many of these species are of medical and economic importance. In this review we present an overview of the midgut and the digestive system of insects with an emphasis on the order Paraneoptera and differences found across phylogenetic groups. We discuss the importance of the PMM in Hemiptera and the apparent conservation of this structure among hemipteran groups, suggesting that the basic mechanism of PMM production is the same for different hemipteran species. We propose that the PMM is intimately involved in the interaction with parasites and as such should be a target for biological and chemical control of hemipteran insects of economic and medical importance.

Efficient capture of natural history data reveals prey conservatism of cryptic termite predators.

Stenophagy, specialization of a clade on a narrow range of taxa, has not been well studied in speciose clades of predators, principally due to the difficulty of obtaining adequate natural history data. The pantropical Salyavatinae (Hemiptera: Reduviidae; 17 genera, 107 species) contains members with enigmatic morphology and specialized behavior for feeding on termites. All Salyavatinae are suspected specialist termite predators; however, existing observations are limited to seven species. Prior analyses indicate that Salyavatinae may be paraphyletic with respect to another subfamily, Sphaeridopinae, also hypothesized to feed on termites. A molecular phylogeny of these putative termite assassins is here constructed using seven loci from 28 species in nine genera and is used in a dating analysis to shed light on the timing of Neotropical colonization by this primarily Old World clade. DNA extracted from gut contents of 50 individuals was assayed using PCR with prey-specific primers.Molecular assays, along with recent photographs and observations, provide substantial evidence that this clade feeds specifically upon termites, documenting 28 new individual associations. Our phylogeny supports a sister group relationship of the Neotropical genus Salyavata with Sphaeridopinae. Termite association data combined with our phylogeny provide evidence of previously unknown prey conservatism among clades of one of the most diverse groups of specialist termite predators.

Neotropical Physoderinae revisited, with description of a new, sexually dimorphic species of Leptophysoderes Weirauch (Hemiptera: Reduviidae).

The small reduviid subfamily Physoderinae has the greatest species diversity in the Oriental region and Madagascar. Only the two monotypic genera Cryptophysoderes Wygodzinsky and Maldonado and Leptophysoderes Weirauch are currently known from the Neotropical region. We here describe and document a new, sexually dimorphic species of Physoderinae, Leptophysoderes sarapiqui sp. nov. from Costa Rica. The generic diagnosis of Leptophysoderes is modified to accommodate the new species. Females and immatures of Leptophysoderes are documented for the first time.

Geographic variation on biological parameters of Meccus picturatus (Usinger), 1939 (Hemiptera: Reduviidae).

The biological parameters related to the life cycles of three populations of Meccus picturatus (Usinger) (Hemiptera: Reduviidae), one of the main vectors of Trypanosoma cruzi Chagas (Trypanosomatida: Trypanosomatidae), were evaluated. A cohort of each of three populations from geographically isolated localities in western Mexico was maintained under similar laboratory conditions, after which all three populations were compared to each other. In each cohort, 50.9 to 72.1% of nymphs completed the cycle. The average time from N1 to adult was approximately 175 days and different for the three studied cohorts. The number of blood meals between molts varied from one to three. The hatching rates as well as the fecundity per female per day were different among the three studied populations. Our results show that the three isolated populations are statistically different in some parameters from each other, which points to the importance of studying the biological characteristics of local populations of triatomines for estimating their capacity of transmitting T. cruzi to reservoir hosts.

Biological characteristics of geographically isolated populations of Meccus mazzottii (Hemiptera: Reduviidae) in southern Mexico.

Chagas disease, caused by Trypanosoma cruzi Chagas, is one of the most epidemiologically important vector-borne zoonoses in Mexico. Among the 32 reported triatomine species from Mexico, Meccus mazzottii (Usinger) (Hemiptera: Reduviidae) is one of the most important vectors of T. cruzi in the southern part of the country. Variability among populations of triatomines has been recorded for several species (Meccus longipennis (Usinger) and Meccus pallidipennis (Stal)) that are closely related to M. mazzottii, showing an apparent influence of local environmental conditions on the biology of each population, which could modify the impact of vector control measurements. Therefore, this study sought to compare the biological features of populations of M. mazzottii from two geographically far apart areas that have similar environmental characteristics and to compare populations from close geographical areas that have different environmental characteristics. The mean longevity, percentages of mortality of nymphs, the total mean number of bloodmeals to molt (considered instar by instar), the mean number of eggs laid by females, and the percentage of hatched eggs were similar between the two localities that are geographically far apart but have similar environmental characteristics. On the other hand, important differences were noticed when a comparison was carried out on the two localities with similar environmental conditions with respect to that locality with different conditions, independent of geographic distance. Most of the studied parameters led us to conclude that the three studied populations are very highly influenced by local environmental conditions. The results of this study indicate the importance of studying the biological characteristics of local populations of triatomines to carry out specific control measurements, instead of using standard ones that could fail if they are not adapted to the target population.

Distribution of Zelus longipes (Hemiptera: Reduviidae) in south Florida corn fields and its functional response to corn-infesting picture-winged flies (Diptera: Ulidiidae).

The milkweed assassin bug, Zelus longipes (L.) (Hemiptera: Reduviidae), is a generalist predator and a potential biological control agent of picture-winged flies (Diptera: Ulidiidae), which cause considerable economic damage to sweet corn yields in Florida. We studied the potential of Z. longipes as a biocontrol agent of four ulidiid pests in corn fields: Euxesta stigmatias Loew, Euxesta eluta Loew, Euxesta annonae F., and Chaetopsis massyla Walker. Within-plant and within-field distributions of Z. longipes and ulidiids and functional responses of Z. longipes to ulidiid prey were determined. Highest numbers of Z. longipes and ulidiids in the R1, R2, and R3 corn stages were generally in the basal or middle leaves at 09:00 h EST, ears at 13:00 h EST, and top and tassel at 17:00 h EST. Hence, there seemed to be a coordinated migration of Z. longipes and ulidiids from the lowest to the highest parts of the corn plant during the day. Within the corn field, aggregated (clumped) distributions were most common for Z. longipes and ulidiids especially in the later R2 and R3 stages based on Taylor's power law, Iwao's patchiness regression, index of dispersion, and Lloyd's patchiness indices of dispersion. However, predator and prey populations were lower in the R1 stage, and there were inconsistent results for dispersion indices among times of day and between predators and prey. Ulidiid distributions in R1 were mostly regular (uniform) at 13:00 h EST, but aggregated at 09:00 h and 17:00 h. However, Z. longipes R1 distributions were mostly aggregated at 13:00 h, but random or regular at 09:00 h and 17:00 h EST. Handling times for male and female Z. longipes were 1.0-1.39 h and 0.67-0.97 h, respectively, and each had a type II functional response to E. stigmatias, E. eluta, and E. annonae and consumed about five flies per day. Although the population abundance of Z. longipes can vary between seasons, it appears to be a promising biocontrol agent of ulidiid flies in corn.

Ovarian nutritional resources during the reproductive cycle of the hematophagous Dipetalogaster maxima (Hemiptera: Reduviidae): focus on lipid metabolism.

In this study, we have analyzed the changes of the ovarian nutritional resources in Dipetalogaster maxima at representative days of the reproductive cycle: previtellogenesis, vitellogenesis, as well as fasting-induced early and late atresia. As expected, the amounts of ovarian lipids, proteins, and glycogen increased significantly from previtellogenesis to vitellogenesis and then, diminished during atresia. However, lipids and protein stores found at the atretic stages were higher in comparison to those registered at previtellogenesis. Specific lipid staining of ovarian tissue sections evidenced remarkable changes in the shape, size, and distribution of lipid droplets throughout the reproductive cycle. The role of lipophorin (Lp) as a yolk protein precursor was analyzed by co-injecting Lp-OG (where OG is Oregon Green) and Lp-DiI (where DiI is 1,10-dioctadecyl-3,3,30,30-tetramethylindocarbocyanine) to follow the entire particle, demonstrating that both probes colocalized mainly in the yolk bodies of vitellogenic oocytes. Immunofluorescence assays also showed that Lp was associated to yolk bodies, supporting its endocytic pathway during vitellogenesis. The involvement of Lp in lipid delivery to oocytes was investigated in vivo by co-injecting fluorescent probes to follow the fate of the entire particle (Lp-DiI) and its lipid cargo (Lp-Bodipy-FA). Lp-DiI was readily incorporated by vitellogenic oocytes and no lipoprotein uptake was observed in terminal follicles of ovaries at atretic stages. Bodipy-FA was promptly transferred to vitellogenic oocytes and, to a much lesser extent, to previtellogenic follicles and to oocytes of ovarian tissue at atretic stages. Colocalization of Lp-DiI and Lp-Bodipy-FA inside yolk bodies indicated the relevance of Lp in the buildup of lipid and protein oocyte stores during vitellogenesis.

Differences on biological attributes of three populations of Meccus pallidipennis Stål (Hemiptera: Reduviidae).

BACKGROUND & OBJECTIVES: Meccus pallidipennis is one of the most epidemiologically important vectors of Trypanosoma cruzi to reservoir hosts in nine states of Mexico. Triatomines occurring in distinct locations normally adapt to local conditions. The aim of this study was to examine the biological attributes of three populations of M. pallidipennis from areas with different environmental characteristics as a factor influencing the triatomine capacity for T. cruzi transmission. METHODS: The values of biological parameters related to the life cycle, the number of blood meals to molt to next instar, fecundity and percentage of females after a biological cycle of three populations of M. pallidipennis were evaluated. A cohort of each of the three studied populations from different geographical areas of Mexico was maintained under similar laboratory conditions and then compared with each other. RESULTS: The life cycle was less than six months in all the studied cohorts, with differences among them. The number of blood meals to molt was lower for the cohort from Izϊcar de Matamoros. Laid eggs per day per female was lower for the cohort from Luvianos. In contrast, no important differences were recorded on the percentage of mortality, egg eclosion rate or percentages of obtained females. INTERPRETATION & CONCLUSION: It was found that an important level of heterogeneity exist between the three studied populations of M. pallidipennis, apparently influenced by the remarkable differences on environmental conditions on the localities where the founders were initially collected, that emphasizes the necessity of studies on local populations of triatomines.