Comparative biology of the two sister species of Triatominae (Hemiptera: Reduviidae) / Biologia comparativa de duas espécies irmãs de Triatominae (Hemiptera: Reduviidae)

INTRODUCTION: Triatoma pseudomaculata and T. wygodzinskyi (Hemiptera: Reduviidae: Triatominae) are two Brazilian vectors of Chagas disease. The first is an arboricolous species in sylvatic environment and considered a vector of T. cruzi in peridomestic structures; the second, a rupicolous species in the wild environment of no epidemiological importance. In order to test the assumption that sister species share biological traits, comparative studies of their development cycle and blood ingestion were conducted. METHODS: Eggs laid by five field females of each species were randomly selected. The nymphs were observed daily and fed on mice weekly. The time required to pass through the different stages to adulthood was recorded in days. The triatomines were weighed individually before and after feeding. The mortality rate according to each nymphal stage was calculated. RESULTS AND CONCLUSIONS: Analysis of the results shows that they display only minor biological differences even though they exhibit a distinct ecology. This suggests that the biological traits are important criteria to determine the relationship between species.

INTRODUÇÃO: Triatoma pseudomaculata e T. wygodzinskyi (Hemiptera: Reduviidae: Triatominae) são dois vetores Brasileiros da doença de Chagas. A primeira é uma espécie arborícola em ambiente silvestre e considerada vetor do T. cruzi em estruturas peridomesticas. A segunda é rupícola em ambientes silvestres e sem importância epidemiológica. Com o objetivo de testar a hipótese que espécies irmãs compartilham características semelhantes, realizamos um estudo comparativo do ciclo biológico e ingesta alimentar. MÉTODOS: Ovos pertencentes a cinco fêmeas de cada espécie provenientes do campo foram selecionados aleatoriamente. As ninfas foram observadas diariamente e alimentadas com camundongos semanalmente. O tempo requerido para passar até o estágio adulto foi registrado em dias. Os triatomíneos foram pesados individualmente antes e depois da alimentação. A mortalidade de cada estágio foi calculada. RESULTADOS E CONCLUSÕES: Analise dos resultados mostram que eles exibem pequenas diferencias biológicas apesar de apresentarem diferenças marcantes quanto a sua ecologia. Isso sugere que as características biológicos são critérios importantes para determinar a relação entre as espécies.

Ciclo biológico em laboratório de Rhodnius brethesi Matta, 1919 (Hemiptera, Reduviidae, Triatominae), potencial vetor silvestre da doença de Chagas na Amazônia / Life cycle of Rhodnius brethesi Matta, 1919 (Hemiptera, Reduviidae, Triatominae), a potential vector of Chagas disease in the Amazon region

R. brethesi is a sylvatic species from the Amazon region; it has been incriminated as responsible for the transmission of Chagas disease in collectors of piaçaba in this region. The aim of present study was to investigate the efficiency of these insects as potential vectors of Trypanosoma cruzi. Aspects related with feeding and defecation patterns, life time, and mortality had been observed in each instar of R. brethesi. We use 5th instar nymphs to get adults virgins, after the moulting 3 groups with 6 females and 2 males each were created to obtain eggs. After hatching, 1st instar nymphs had been weighed and kept in bottles until the next moult. Insects were fed once a week in mice. Results showed that the average period of incubation was 17 days, the number of blood meal was increasing from the 1st to the 5th instar nymph with 7 (average) to become adult, a significative numbers of the defecations occurring immediately after the bloodmeals. The total percentual of mortality was 16 percent. This results suggests that this species presents a good exploitation of blood meals and a brief nymphal development in laboratory conditions reflecting its behavior in sylvatic environments.

Foco de doença de Chagas em Arcádia, estado do Rio de Janeiro, Brasil / Source of Chagas disease in Arcádia, state of Rio de Janeiro, Brazil

Following the report of triatomine nymphs in a house in Arcadia, Miguel Pereira, state of Rio de Janeiro, Brazil, the infested dwelling was checked. Several eggs and 46 specimens of Triatoma vitticeps (Stal, 1859) were collected. Among them, adults and nymphal instars accounted for 43.5 percent and 56.5 percent, respectively. Analysis of blood meals showed the ecletism of this species; 24 (52.2 percent) were single feeds, 18 insects (39.1 percent) fed on two hosts and 4 (8.7 percent) on three hosts. Trypanosoma cruzi infection rate of examined specimens was 13 percent. Finally one of the residents of the house was positive for anti-T. cruzi antibodies using indirect immunofluorescence.

Trapping Triatominae in silvatic habitats

Large-scale trials of a trapping system designed to collect silvatic Triatominae are reported. Live-baited adhesive traps were tested in various ecosystems and different triatomine habitats (arboreal and terrestrial). The trials were always successful, with a rate of positive habitats generally over 20 percent and reaching 48.4 percent for palm trees of the Amazon basin. Eleven species of Triatominae belonging to the three genera of public health importance (Triatoma, Rhodnius and Panstrongylus) were captured. This trapping system provides an effective way to detect the presence of triatomines in terrestrial and arboreal silvatic habitats and represents a promising tool for ecological studies. Various lines of research are contemplated to improve the performance of this trapping system

Influência da temperatura e umidade no desenvolvimento ninfal de Rhodnius robustus / Influence of temperature and humidity on the nymphal development of Rhodnius robustus

OBJETIVO: Avaliar as diferenças significativas de desenvolvimento ninfal da espécie Rhodnius robustus Larrousse, 1927, submetida a diferentes condiçöes de temperatura e umidade, que se encontra distribuída na regiäo Norte do Brasil (Acre, Amazonas e Pará) e na Colômbia, no Equador, no Peru e na Venezuela. MÉTODOS: Formaram-se três grupos de Rhodnius robustus, mantidos em diferentes condiçöes de laboratório: 33/40 (33+/-1oC e 40+/-5 por cento UR ó umidade relativa), 33/70 (33+/-1oC e 70+/-5 por cento UR) e 28/70 (28+/-1oC e 70+/-5 por cento UR), para observar o período de incubaçäo dos ovos, o desenvolvimento de cada estádio, os percentuais de mortalidade e os número de repastos realizados. RESULTADOS: O menor período médio de desenvolvimento ninfal foi observado no grupo 28/70 com as médias: 14,4; 17,3; 20,3; 22,8 e 40. O desenvolvimento embrionário apresentou diferenças significativas entre os tratamentos utilizados (p<0,01). O número de repastos teve aumento gradual com a aproximaçäo da fase adulta em todos os grupos testados, exceto no terceiro estádio do grupo 33/70. Os menores percentuais de mortalidade foram os do grupo 28/70. CONCLUSOES: Temperaturas elevadas, independentes das umidades associadas, podem acelerar o ciclo biológico da espécie. Entretanto, elas podem prejudicar a sobrevivência das colônias, impedindo sua manutençäo em laboratório

Estádios ninfais / Nymphal stages

Aborda os estágios ninfais da eclosäo do ovo até chegar à fase adulta

Alguns aspectos da biologia de Triatoma pseudomaculata Correa & Espinola, 1964, em condicoes de laboratorio (Hemiptera: Reduviidae: Triatominae) / Biology of Triatoma pseudomaculata Correa & Espinola, 1964, under laboratory conditions (Hemiptera: Reduviidae: Triatominae)

Observations were made on the evolutive cycle of Triatoma pseudomaculata, held under laboratory conditions, fed weekly on bird (pigeon). Of 60 eggs obtained, only 34 nymphs reached the adult stage in a period of X(S)=398ñ76 days. The following parameters were observed: the time immature stages took to develop from egg to adult emergence; the occurence of the first meal; the time-lapse between the presenting of the blood-meal and the begining of feeding; time of feeding; amount of blood ingested; variation of weight 24 hr after the blood-meal and unit the next blood-meal; and the defecation pattern. The experimental was carried out for 20 months, held in BOD incubator with the average of temperature and humidity of 28ñ1ºC and 80ñ5 per cent RU, respectively.

Biologia do Triatoma nitida Usinger, 1939 em laboratório (Hemiptera: Reduviidae)

Biology of Triatoma nitida Usinger, 1939 under Laboratory Conditions - Triatoma nitida is a wild species occurring in Mexico and Central America. In order to establish the length of its life cycle and transmission potential, the following parameters were observed: the incubation period, the interval between hatching, or moulting, and the first feeding; the number of blood meals and the time of development. The time-lapse before the bite, the length of feeding and the interval between the end of the blood meal and defecation, as well as the site of defecation were also analyzed. Average length of the egg incubation period was 18.2 days. Time interval between the food source offering and the bite was less than 4 min in 60//of the analyzed cases, except in the fifth instar, where only 38//of the insects began feeding in less than 5 min. The blood-sucking period was long and rising until the fifth instar, decreasing in adults, and ranging from 1 min to 2 and a half hours. Only 26//of the blood meals were followed by defecations within 20 min. The average length of the life cycle was 897.5 days.

Estudos bionômicos de Dipetalogaster maximus (Uhler, 1894) (Hemiptera, Reduviidae, Triatominae): III. Dinâmica populacional / Bionomics studies of Dipetalogaster maximus (Uhler, 1894) (Hemiptera, Reduviidae, Triatominae): III. Population dynamics

Bionomics studies of Dipetalogaster maximus (Uhler, 1894) (Hemiptera, Reduviidae, Triatominae). III. Population dynamics - A population dynamics study of D. maximus was caried out under laboratory condictions (28-C e 65% ñ 5% U.R.) and the methodology was the same that have been used for hearing this insects. In order to evaluate the population growth rate of this species, during a 24 months period, five colonies started with a couple recently emerged were observed. Each couple (a male and a female) was mantained in a glass container measuring 20 cm of diameter and 20 cm in height with filter paper on the botton. The insects were monthly feeding with normal mice blood, and at this day the number of eggs, nymphal stages and adults was registered. All graphical representations of the populations growth rate showed the same shape. It was found that the average of nymphal stage represented 64.31% of the hole population whereas the oviposition curved showed to be inverse to this one (28.57%) a small percentage of adults was found: males 3.85% and females 3.12%. In this study observations on the biologycal cycle, longevity and fertility rates were also carried out

Biologia do triatoma vitticeps (Stal, 1859) Under laboratory conditions (Hemiptera: Reduvidae: Triatomidae) - II. Resistance to starvation

Em prosseguimento ao estudo da biologia do Triatoma vitticeps (Gonçalves et al., 1988), foram feitas observaçöes sobre a sua resistência ao jejum. Dos 286 ovos obtidos, apenas 201 eclodiram e atingiram o estádio pretendido para as observaçöes. Os demais näo eclodiram, näo completaram a muda ou morreram sem motivo aparente. As ninfas foram acondicionadas, individualmente em frascos de Borrel, devidamente registrados. Para a alimentaçäo foram utilizados camundongos e a medida que as ninfas atingiam o estágio pretendido a alimentaçäo era suspensa até ocorrer a morte. A avaliaçäo da resistência ao jejum foi feita da seguinte forma: o intervalo de dias entre o último repasto e a morte e entre a muda e a morte. Verificou-se que a resistência está diretamente relacionada com a fase de desenvolvimento. Para os parâmetros último repasto/morte e muda/morte, ambos os sexos foram menos resistentes do que as ninfas de 3§ e 2§ estádios, respectivamente. O experimento teve duraçäo de 15 meses e neste período as temperaturas máxima e mínima e a umidade relativa do ar variaram em média de 25ñ 2-C e 81 ñ 3½ UR, respectivamente. O material foi proveniente da criaçäo de triatomíneos mantida no Departamento de Entomologia do Instituto Oswaldo Cruz