ABSTRACT
ABSTRACT: Cockroaches are insects that can accommodate diets of different composition, including lignocellulosic materials. Digestion of these compounds is achieved by the insect's own enzymes and also by enzymes produced by gut symbionts. The presence of different and modular bacterial phyla on the cockroach gut tract suggests that this insect could be an interesting model to study the organization of gut bacterial communities associated with the digestion of different lignocellulosic diets. Thus, changes in the diversity of gut associated bacterial communities of insects exposed to such diets could give useful insights on how to improve hemicellulose and cellulose breakdown systems. In this work, through sequence analysis of 16S rRNA clone libraries, we compared the phylogenetic diversity and composition of gut associated bacteria in the cockroach Periplaneta americana collected in the wild-types or kept on two different diets: sugarcane bagasse and crystalline cellulose. These high fiber diets favor the predominance of some bacterial phyla, such as Firmicutes, when compared to wild-types cockroaches. Our data show a high bacterial diversity in P. americana gut, with communities composed mostly by the phyla Bacteroidetes, Firmicutes, Proteobacteria and Synergistetes. Our data show that the composition and diversity of gut bacterial communities could be modulated by diet composition. The increased presence of Firmicutes in sugarcane bagasse and crystalline cellulose-fed animals suggests that these bacteria are strongly involved in lignocellulose digestion in cockroach guts. BACKGROUND: Cockroaches are omnivorous animals that can incorporate in their diets food of different composition, including lignocellulosic materials. Digestion of these compounds is achieved by the insect's own enzymes and also by enzymes produced by gut symbiont. However, the influence of diet with different fiber contents on gut bacterial communities and how this affects the digestion of cockroaches is still unclear. The presence of some bacterial phyla on gut tract suggests that cockroaches could be an interesting model to study the organization of gut bacterial communities during digestion of different lignocellulosic diets. Knowledge about the changes in diversity of gut associated bacterial communities of insects exposed to such diets could give interesting insights on how to improve hemicellulose and cellulose breakdown systems. METHODOLOGY/PRINCIPAL FINDINGS: We compared the phylogenetic diversity and composition of gut associated bacteria in the cockroach P. americana caught on the wild or kept on two different diets: sugarcane bagasse and crystalline cellulose. For this purpose we constructed bacterial 16S rRNA gene libraries which showed that a diet rich in cellulose and sugarcane bagasse favors the predominance of some bacterial phyla, more remarkably Firmicutes, when compared to wild cockroaches. Rarefaction analysis, LIBSHUFF and UniFrac PCA comparisons showed that gene libraries of wild insects were the most diverse, followed by sugarcane bagasse fed and then cellulose fed animals. It is also noteworthy that cellulose and sugarcane bagasse gene libraries resemble each other. CONCLUSION/SIGNIFICANCE: Our data show a high bacterial diversity in P. americana gut, with communities composed mostly by the phyla Bacteroidetes, Firmicutes, Proteobacteria and Synergistetes. The composition and diversity of gut bacterial communities could be modulated by font of diet composition. The increased presence of Firmicutes in sugarcane bagasse and crystalline cellulose-fed animals suggests that these bacteria are strongly involved in lignocellulose digestion in cockroach guts.
ABSTRACT
Four species of Tephritoidea, three from genus Anastrepha: A. obliqua (Macquart), A. sororcula Zucchi and A. serpentina (Wiedemann), and one from genus Ceratitis, C. capitata (Wiedemann) were compared based on puparium morphology and application of the Heteroduplex Mobility Assay (HMA). Puparia were characterized for the first time using the spiracular posterior plate morphology. Application of HMA allowed the detection of variability in the D2 domain from 28S rRNA gene in all four species (confirmed by sequencing). This is a fast, simple, sensitive and inexpensive assay that was used for the first time in the analysis of two Tephritoidea genera. The detected variability suggests that the tecnique has great potential for rapid determination of infestations with two or more species in the same host fruit.
Foram comparadas com base na morfologia do pupário e na técnica de HMA (Heteroduplex Mobility Assay)) quatro espécies de Tephritoidea, três delas pertencentes ao gênero Anastrepha, A. obliqua (Macquart), A. sororcula Zucchi e A. serpentina (Wiedemann) e uma do gênero Ceratitis, C. capitata (Wiedemann). Os pupários foram caracterizados pela primeira vez com base na morfologia da placa espiracular posterior. A aplicação da técnica de HMA possibilitou a detecção de variabilidade no segmento D2 do gene 28S rRNA nas quatro espécies (confirmada por seqüenciamento). Esta é uma técnica rápida, simples, sensível e barata que é aplicada pela primeira vez na análise de dois gêneros de Tephritoidea. A variabilidade observada sugere grande potencial da técnica no caso da determinação da infestação por duas ou mais espécies num mesmo fruto hospedeiro.
Subject(s)
Tephritidae/anatomy & histology , Tephritidae/genetics , Heteroduplex Analysis/methods , Pest Control , Pupa , Tephritidae/classificationABSTRACT
A emergência e os fatores de mortalidade pupal de Anastrepha obliqua (Macq.) (Diptera: Tephritidae) durante a frutificação da planta hospedeira Spondias dulcis L. (Anacardiaceae) foram estudados no campo e no laboratório em Sertãozinho, SP. Nas duas condições experimentais, após os períodos de emergência, foram registrados os números de pupários fechados e abertos. Os números de moscas e parasitóides emergidos dos pupários foram registrados. Os pupários fechados foram analisados e, conforme o estado da pupa dentro do pupário, as mesmas foram classificadas em vivas (dormentes) e mortas. Os fatores de mortalidade considerados foram: dessecação, doenças e predação. Foramanalisados 1204 pupários, sendo que de 53% emergiram adultos e 47% permaneceram fechados; do total de pupários fechados, 25,3% eram pupas em estado de dormência e 21,7% eram pupas mortas por predadores, doenças e dessecação. Das pupas em estado de dormência, 17,8% eram moscas e somente 0,2% completaram o estágio pupal; 7,5% continham parasitóides, sendo que 4,7% deles emergiram. Oparasitismo inicial foi de 8,6% e após a emergência das pupas em dormência aumentou para 15,5%. A ação predatória em condições naturais foi acentuada, especialmente quando o tempo de exposição foi prolongado. Em condições de laboratório, a dessecação foi o principal fator de mortalidade pupal. O parasitismo também contribuiu significativamente para a mortalidade pupal enquanto que, as doenças provocadas por patógenos (fungos e bactérias), parecem ter sido menos significativas. Predadores e parasitóides atuaram efetivamente no controle populacional dessa mosca-das-frutas. Entretanto, os fatores que regulam o estado de dormência, ainda devem ser determinados...
The emergence and pupal mortality factors of Anastrepha obliqua (Macq.) (Diptera: Tephritidae) along the fruiting season of the host plant, Spondias dulcis L. (Anarcadiaceae), were studied in Sertãozinho, SP, Brazil, under field and laboratory conditions. Eclosed and uneclosed puparia were recorded in two experimental conditions. The number of emerged flies and parasitoids weredetermined in the eclosed puparia. The uneclosed puparia were inspected and classified into living (dormant) and dead. The following pupal mortality factors were considered: disease, desiccation, predation and parasitism. Out of the total of 1,204 puparia analyzed, 53% emerged and 47% remained uneclosed. Out of the uneclosed puparia, 25.3% contained dormant pupae and 21.7% showed no signs of emergence. Among the dormant pupae, 17.8% were flies, 0.2% of which emerged; 7.5% were parasitoids, 4.7% of them emerged. The initial parasitism was 8.6%, increasing to 15.3% after theemergence of dormant pupae. Predatory activity (natural condition), especially when time of exposure was long, and desiccation (laboratory condition) were the predominant causes of pupal mortality. Variation in mortality caused by parasites and pathogens (bacteria and fungi) seems to play a minor role. Control by predators on fruit fly population is significant. However, the factors, which regulate induction, maintenance and termination of dormancy, are still to be determined. An estimate of the dormancy and of the biotic and abiotic pupal mortality factors are essential to understand the adaptivestrategies of A.obliqua and its parasitoids and to develop effective methods of control in tropical regions.
