Ecomorphological variation of the Triatoma guasayana wing shape in semi-arid Chaco region.

Triatoma guasayana (Hemiptera, Reduviidae), considered a secondary vector of Chagas disease, invades rural dwellings through flight dispersal during the warm season in semi-arid Chaco of Argentina. The objective of this study was to define and compare morphometrics features in the relative body size and wing shape of T. guasayana related to temperature and rainfall between spring, summer and end of summer. A total of 188 adults were collected in rural communities in the northwest of the province of Córdoba (central Argentina). Relative body size [body length (mm) / wing length (mm)] and 11 landmarks on the right wing were recorded. The temperature ( °C) and precipitation (mm) data were extracted from the MODIS sensor and Terra Climate dataset, respectively. Correlations between climatic variables and morphological variation were analyzed using Partial Least Square (PLS). Males at the end of summer were smaller than those at spring or summer (F = 4.48; df = 2; p = 0.01), whereas females were similar in relative body size at all seasons (F = 0.76; df = 2; p = 0.47). The PLS in males showed a correlation between wing shape and temperature (r = 0.48; p = 0.03) and precipitation (r = 0.50; p = 0.02) while in females only the temperature was the correlation significant (r = 0.35; p = 0.03). Triatoma guasayana has elongated and thin wings in spring that become short and wide at the end of summer. The morphotype of early summer could allow sustained long-duration flights, while the morphotype of end of summer would be related to short flights, correlated with the dispersive behavior of the species. The results in this study suggest that wing morphology of T. guasayana has phenotypic plasticity, and that temperature and rainfall could be considered modulator factors during the developmental stage.

Histology of folicular development of hybrids between Triatoma infestans Klug, 1864 and Triatoma platensis Neiva, 1913 (Hemiptera: Heteroptera) / HISTOLOGÍA DEL DESARROLLO FOLICULAR DE HÍBRIDOS ENTRE Triatoma infestans Klug, 1864 Y Triatoma platensis Neiva, 1913 (HEMIPTERA: HETEROPTERA)

ABSTRACT Triatoma infestans and Triatoma platensis are interfertile species that frequently share ecotopes and produce natural fertile hybrids. Interspecific crossing allows the production of more suitable hybrid genotypes capable of colonizing new habitats. Therefore, studies of reproductive aspects in hybrids are of great importance. In this sense, oogenesis, a process that involves the development of the oocyte and allows the formation of viable eggs, is a relevant aspect. In this study, histological aspects focused on the follicular development of experimental hybrids were characterized. To do this, the ovaries of35 hybrid females were removed, paraffin-embedded and stained with hematoxylin-eosin. The development of the follicular epithelium and the oocyte in the stages of previtellogenesis and vitellogenesis were characterized, finding that the oogenesis of the hybrid females is well defined producing viable eggs and that the changes occurred at the histological level resemble those registered in T. infestans.

RESUMEN Triatoma infestans y Triatoma platensis son especies interfértiles que en ocasiones comparten ecotopos y producen híbridos fértiles naturales. El cruzamiento interespecífico podría permitir la producción de genotipos híbridos capaces de colonizar nuevos hábitats. Por ello, los estudios de aspectos reproductivos sobre estos organismos son de gran importancia. En este sentido la oogénesis, proceso que implica el desarrollo del ovocito y permite la formación de huevos viables, es un aspecto relevante. En este estudio se caracterizaron aspectos histológicos enfocados en el desarrollo folicular de híbridos experimentales. Para ello, se extrajeron los ovarios de 35 hembras híbrido, se embebieron en parafina y colorearon con hematoxilina-eosina. Se caracterizó el desarrollo del epitelio folicular y del ovocito en las etapas de previtelogénesis y vitelogénesis, encontrándose que la oogénesis de las hembras híbrido se encuentra bien definida produciendo huevos viables y que los cambios ocurridos a nivel histológico se asemejan a los registrados en T. infestans.

Characterization of melanic and non-melanic forms in domestic and peridomestic populations of Triatoma infestans (Hemiptera: Reduviidae).

BACKGROUND: Melanic (dark) morphs have been barely reported in peridomestic and sylvatic conditions for Triatoma infestans, the most important vector of Chagas disease in the Southern Cone of South America. Adults with dark and small yellow markings on the connexivum were collected after manual searches conducted by technical personnel in 62 domiciliary units in Cruz del Eje, Córdoba Province, Argentina. The last community-wide insecticide spraying campaign before the study had been conducted three years earlier. We investigated if there was a measurable color morph variation (melanic and non-melanic) in wings and connexivum; we determined infestation, distribution of melanic and non-melanic forms, and correspondence of colorimetric variation with variations in morphology (wing size and shape and body length), development (wing fluctuating asymmetry), physiology (nutritional status) or behaviour (flight initiation). RESULTS: Forty-nine females, 54 males and 217 nymphs were collected in 24 domiciliary units. House infestation and colonization were 53% and 47%, respectively. Most of the T. infestans individuals (83.2%) were collected in chicken coops; intradomicile infestation was recorded in only one case. The chromatic cluster analysis showed two well-defined groups: melanic and non-melanic. The melanic group included 17 (35%) females and 25 (46%) males. Peridomestic infestation was lower for melanic than for non-melanic adults. Melanic morphs were collected in houses from several localities. Sexual dimorphisms were confirmed by morphometric measurements. Body length was large in melanic adults (P < 0.01 only for males). Differences between groups were significant for wing size and shape, but not for weight or weight/body length ratio. Melanic females and males showed significantly higher fluctuating asymmetry (FA) indices than their non-melanic counterparts. CONCLUSIONS: This is the second report of melanic forms of T. infestans in domestic and peridomestic habitats in the Dry Chaco region of Argentina. Although non-melanic adults exhibited a higher infestation rate, melanic adults were widespread in the area and were collected in the infested domicile and in most types of peridomestic annexes. Differences in morphometric variables between groups might be due to different ecological adaptations. The higher FA levels observed in melanic individuals suggest a higher developmental instability and a selective advantage of non-melanic individuals in domestic and peridomestic habitats.

Morphometric variability among the species of the Sordida subcomplex (Hemiptera: Reduviidae: Triatominae): evidence for differentiation across the distribution range of Triatoma sordida.

BACKGROUND: The Sordida subcomplex (Triatominae) comprises four species, Triatoma garciabesi, T. guasayana, T. patagonica and T. sordida, which differ in epidemiological importance and adaptations to human environments. Some morphological similarities among species make taxonomic identification, population differentiation and species delimitation controversial. Triatoma garciabesi and T. sordida are the most similar species, having been considered alternatively two and a single species until T. garciabesi was re-validated, mostly based on the morphology of male genitalia. More recently, T. sordida from Argentina has been proposed as a new cryptic species distinguishable from T. sordida from Brazil, Bolivia and Paraguay by cytogenetics. We studied linear and geometric morphometry of the head, wings and pronotum in populations of these species aiming to find phenotypic markers for their discrimination, especially between T. sordida and T. garciabesi, and if any set of variables that validates T. sordida from Argentina as a new species. RESULTS: Head width and pronotum length were the linear variables that best differentiated species. Geometric morphometry revealed significant Mahalanobis distances in wing shape between all pairwise comparisons. Triatoma patagonica exhibited the best discrimination and T. garciabesi overlapped the distribution of the other species in the morphometric space of the first two DFA axes. Head shape showed differentiation between all pairs of species except for T. garciabesi and T. sordida. Pronotum shape did not differentiate T. garciabesi from T. guasayana. The comparison between T. garciabesi and T. sordida from Argentina and T. sordida from Brazil and Bolivia revealed low differentiation based on head and pronotum linear measurements. Pronotum and wing shape were different between T. garciabesi and T. sordida from Brazil and Bolivia and T. sordida from Argentina. Head shape did not differentiate T. garciabesi from T. sordida from Argentina. CONCLUSIONS: Wing shape best delimited the four species phenotypically. The proposed cryptic species, T. sordida from Argentina, differed from T. sordida from Brazil and Bolivia in all measured shape traits, suggesting that the putative new species may not be cryptic. Additional studies integrating cytogenetic, phenotypic and molecular markers, as well as cross-breeding experiments are needed to confirm if these three entities represent true biological species.

Effects of blood meal source on food resource use and reproduction in Triatoma patagonica Del Ponte (Hemiptera, Reduviidae).

Triatoma patagonica (Del Ponte, 1929) (Hemiptera-Reduviidae) is a peridomestic vector of Chagas disease that has been frequently found colonizing peridomestic structures in several localities in Argentina. Studying relationships between feeding and reproductive factors is important because these traits regulate population density and define vectorial capacity. Since T. patagonica can circulate among peridomestic structures taking blood from both bird and mammal hosts, we evaluated the extent to which different blood meal sources affect food resource use and reproductive parameters. We used 5(th) instar nymphs and females that fed on either guinea pigs or pigeons to estimate food resource use. We estimated reproductive parameters in adults that fed on these sources. Nymphs and adults showed differences in blood consumption between feeding sources. Females fed on pigeons ingested more blood and needed a higher amount of blood to produce an egg than females fed on guinea pigs. There were no differences in the number of eggs laid and hatched between insects fed on different feeding sources. The higher amount of blood ingested and consumed by T. patagonica fed on pigeons did not translate into higher fecundity or fertility. The lower amount of guinea pig blood ingested was offset by its high nutritional quality.

Comparison of feeding and defecation patterns between fifth-instar nymphs of Triatoma patagonica (Del Ponte, 1929) and Triatoma infestans (Klug, 1934) under laboratory conditions.

Among the vectors of Chagas disease, Triatoma patagonica is a species in the process of adaptation to the human environment. However, its vector competence is not well known. This study had the aim of evaluating and comparing feeding and defecation patterns among fifth-instar nymphs of Triatoma patagonica and Triatoma infestans that were fed ad libitum. The results showed that nymphs of Triatoma patagonica had a feeding pattern similar to that of Triatoma infestans. Sixty nine percent and 58% of nymphs of Triatoma patagonica and Triatoma infestans, respectively, produced their first defecation within five minutes after being fed. Triatoma patagonica defecated during feeding, with an average time until first defecation that was shorter than that of Triatoma infestans (3.4 and 6.2 min, respectively). The nymphs of Triatoma patagonica were capable of defecating during or immediately after feeding.

Comparison of feeding and defecation patterns between fifth-instar nymphs of Triatoma patagonica (Del Ponte, 1929) and Triatoma infestans (Klug, 1934) under laboratory conditions / Comparação dos padrões alimentar e de defecação em ninfas de quinto estádio de Triatoma patagonica (Del Ponte, 1929) e Triatoma infestans (Klug, 1934), em condições de laboratório

Among the vectors of Chagas disease, Triatoma patagonica is a species in the process of adaptation to the human environment. However, its vector competence is not well known. This study had the aim of evaluating and comparing feeding and defecation patterns among fifth-instar nymphs of Triatoma patagonica and Triatoma infestans that were fed ad libitum. The results showed that nymphs of Triatoma patagonica had a feeding pattern similar to that of Triatoma infestans. Sixty nine percent and 58 percent of nymphs of Triatoma patagonica and Triatoma infestans, respectively, produced their first defecation within five minutes after being fed. Triatoma patagonica defecated during feeding, with an average time until first defecation that was shorter than that of Triatoma infestans (3.4 and 6.2 min, respectively). The nymphs of Triatoma patagonica were capable of defecating during or immediately after feeding.

Entre os vetores da doença de Chagas, Triatoma patagonica é uma espécie que se encontra em processo de adaptação ao ambiente humano; embora sua competência vetorial não seja bem conhecida. O estudo teve como objetivo avaliar e comparar padrões de alimentação e defecação em ninfas de quinto estádio de Triatoma patagonica e Triatoma infestans ad libitum. Os resultados mostraram que as ninfas de Triatoma patagonica apresentou padrõe de alimentação semelhante a Triatoma infestans. Sessenta e nove por cento e 58 por cento das ninfas de Triatoma patagonica e Triatoma infestans respectivamente, realizaram a primeira defecação cinco minutos após de serem alimentadas; sendo que a primeira defecou durante a alimentação, com um tempo médio de dejeção menor do que para Triatoma infestans (3,4 vs 6,2 respectivamente). As ninfas de Triatoma patagonica foram capazes de defecar durante ou imediatamente após de se alimentarem.