Tissue localization of the endosymbiotic bacterium "Candidatus Blochmannia floridanus" in adults and larvae of the carpenter ant Camponotus floridanus

The distribution of endosymbiotic bacteria in different tissues of queens, males, and workers of the carpenter ant Camponotus floridanus was investigated by light and electron microscopy and by in situ hybridization. A large number of bacteria could be detected in bacteriocytes within the midguts of workers, young virgin queens, and males. Large amounts of bacteria were also found in the oocytes of workers and queens. In contrast, bacteria were not present in oocyte-associated cells or in the spermathecae of mature queens, although occasionally a small number of bacteria could be detected in the testis follicles of males. Interestingly, the number of bacteriocytes in mature queens was strongly reduced and the bacteriocytes contained only very few or no bacteria at all, although the endosymbionts were present in huge amounts in the ovaries of the same animals. During embryogenesis of the deposited egg, the bacteria were concentrated in a ring of endodermal tissue destined to become the midgut in later developmental stages. However, during larval development, bacteria could also be detected in other tissues although to a lesser extent. Only in the last-instar larvae were bacteria found exclusively in the midgut tissue within typical bacteriocytes. Tetracycline and rifampin efficiently cleansed C. floridanus workers of their symbionts and the bacteriocytes of these animals still remained empty several months after treatment had ceased. Despite the lack of their endosymbionts, these adult animals were able to survive without any obvious negative effect under normal cultivation conditions.     

Replication of the Endosymbiotic Bacterium Blochmannia floridanus Is Correlated with the Developmental and Reproductive Stages of Its Ant Host

The dynamics of replication of the intracellular endosymbiotic bacterium Blochmannia floridanus was determined during the larval development of its host ant Camponotus floridanus by real-time quantitative PCR. The bacteria were found to proliferate during pupation and immediately after the eclosion of the imagines (adult ants). In older workers the number of bacteria present in the midgut bacteriocytes decreased significantly. In contrast, the bacterial population in the ovaries was dependent on the reproductive state of the animal. An age-dependent degeneration of the midgut bacteriocytes was also investigated by microscopic techniques in males and female castes of the closely related ant species C. herculeanus and C. sericeiventris, respectively, with similar results and supports the concept of age-dependent degeneration of the midgut bacteriocytes in all castes.     

Blochmannia endosymbionts and their host, the ant Camponotus fellah: cuticular hydrocarbons and melanization

Carpenter ants (genus Camponotus) have mutualistic, endosymbiotic bacteria of the genus Blochmannia whose main contribution to their hosts is alimentary. It was also recently demonstrated that they play a role in improving immune function as well. In this study, we show that treatment with an antibiotic produces a physiological response inducing an increase in both the quantity of cuticular hydrocarbons and in the melanization of the cuticle probably due to a nutritive and immunological deficit. We suggest that this is because it enhances the protection the cuticle provides from desiccation and also from invasions by pathogens and parasites. Nevertheless, the cuticular hydrocarbon profile is not modified by the antibiotic treatment, which indicates that nestmate recognition is not modified.     

The endosymbiotic bacterium Holospora obtusa enhances heat-shock gene expression of the host Paramecium caudatum

The bacterium Holospora obtusa is a macronuclear-specific symbiont of the ciliate Paramecium caudatum. H. obtusa-bearing paramecia could survive even after the cells were quickly heated from 25 degrees C to 35 degrees C. To determine whether infection with H. obtusa confers heat shock resistance on its host, we isolated genes homologous to the heat shock protein genes hsp60 and hsp70 from P. caudatum. The deduced amino acid sequences of both cDNAs were highly homologous to hsp family sequences from other eukaryotes. Competitive PCR showed that H. obtusa-free paramecia expressed only trace amounts of hsp60 and hsp70 mRNA at 25 degrees C, but that expression of hsp70 was enhanced immediately after the cells were transferred to 35 degrees C. H. obtusa-bearing paramecia expressed high levels of hsp7O mRNA even at 25 degrees C and the level was further enhanced when the cells were incubated at 35 degrees C. In contrast, the expression pattern of hsp60 mRNA was the same in H. obtusa-bearing as in H. obtusa-free paramecia. These results indicate that infection with its endosymbiont can confer a heat-shock resistant nature on its host cells.     

Population and colony structure of the carpenter ant Camponotus floridanus

The colony and population structure of the carpenter ant, Camponotus floridanus, were investigated by multilocus DNA fingerprinting using simple repeat motifs as probes [e.g. (GATA)₄]. The mating frequency of 15 queens was determined by comparing the fingerprint patterns of the queen and 17–33 of her progeny workers. C. floridanus queens are most probably singly mated, i.e. this species is monandrous and monogynous (one queen per colony). C. floridanus occurs in all counties of mainland Florida and also inhabits most of the Key islands in the southern part of Florida. We tested whether the two mainland populations and the island populations are genetically isolated. Wright's F_ST and Nei's D-value of genetic distance were calculated from intercolonial bandsharing-coefficients. The population of C. floridanus is substructured (F_ST= 0.19 ± 0.09) and the highest degree of genetic distance was found between one of the mainland populations and the island populations (D= 0.35). Our fingerprinting technique could successfully be transferred to 12 other Camponotus species and here also revealed sufficient variability to analyse the genetic structure. In three of these species (C. ligniperdus, C. herculeanus and C. gigas) we could determine the mating frequency of the queen in one or two colonies, respectively.     

Patterns and rates of nucleotide substitution,insertion and deletion in the endosymbiont of ants Blochmannia floridanus

Genome reduction is a general process that has been studied in numerous symbiotic bacteria associated with insects. We investigated the last stages of genome degradation in Blochmannia floridanus, a mutualistic bacterial endosymbiont of the ant Camponotus floridanus. We determined the tempo (rates of insertion and deletion) and mode (size and number of insertion–deletion events) of the process in the last 200 000 years by analysing a total of 16 intergenic regions in several strains of this endosymbiont from different ant populations. We provide the first calculation of the reduction rate for noncoding DNA in this endosymbiont (2.2 × 10^?8 lost nucleotides/site/year) and compare it with the rate of loss in other species. Our results confirm, as it has been observed in other organisms like Buchnera aphidicola or Rickettsia spp., that deletions larger than one nucleotide can still appear in advanced stages of genome reduction and that a substitutional deletion bias exists. However, this bias is not due to a higher proportion of deletion over insertion events but to a few deletion events being larger than the rest. Moreover, we detected a substitutional AT bias that is probably responsible for the increase in the number of the small and moderate indel events in the last stages of genome reduction. Accordingly, we found intrapopulational polymorphisms for the detected microsatellites in contrast to the stability associated with these in free‐living bacteria such as Escherichia coli.     

Influence of host developmental state on host suitability and reproductive biology of the parasitoid Eucelatoria bryani

Eucelatoria bryani Sabrosky (Diptera: Tachinidae) successfully parasitized 2nd through 5th instars and prepupal Heliothis zea (Boddie) (Lepidoptera: Noctuidae) in the laboratory. Percent successful parasitism (that which resulted in the production of adult parasitoid progeny) increased with host developmental state, reaching 95% in 5th instars, but fell to 63% in prepupae. While 25% of the exposed prepupae metamorphosed to pupae, none developed into adults. E. bryani maggots emerged from only 5% of H. zea pupae. The mean number of fly puparia and adults produced per successfully parasitized larva increased with host stadium, reaching 14.5±1.33 (SEM) and 10.6±1.02, respectively, in prepupae. The sex ratio of adult parasitoid progeny per host larval stadium was variable, and did not appear to follow a pattern. A formula for calculating a host favorability index is presented. This index allows a direct comparison of the overall impact and reproductive potential of E. bryani attacking hosts of varying developmental states.

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Résumé Les influences de l'état de développement de l'hôte sur le taux de parasitisme, la production de descendants, l'émergence des adultes et le taux sexuel de la techinaire E. bryani Sabrosky ont été examinés au laboratoire. Un parasitisme réussi,-qui entraîne la formation d'un parasitoïde adulte-, s'effectue dans les chenilles de stades 2 à 5 et dans les prénymphes d'Heliothis zea Boddie. II s'agit d'un élargissement considérable de la gamme connue des tailles convenables d'hôtes. Bien que le parasitisme n'ait jamais réussi avec les chenilles de premier stade, une très forte mortalité, 93% a été observée quand ces petites chenilles ont été exposées à la tachinaire. Pour permettre l'introduction par le larvipositeur des asticots dans la chenille, la mouche perfore la cuticule de l'hôte avec un sclérite modifié; ainsi, une grande partie de la mortalité est provoquée vraisemblablement par le traumatisme dû au parasitoïde. Le succès du parasitisme a augmenté en fonction du développement de l'hôte du second stade (30%) au cinquième stade (95%), pour tomber à 63% dans les prénymphes. Cependant, aucune des prénymphes exposées aux mouches n'a été capable de donner des papillons.Les production moyennes de pupes et de mouches par chenille effectivement parasitée ont augmenté avec le stade de développement de l'hôte pouratteindre dans les prénymphes respectivement 14,5±1,33 et 10,6±1,02. Le taux sexuel des mouches obtenues a été très variable pour les différents stades de développement des chenilles, sans qu'aucune corrélation ait pu être mise en évidence. Une formule permettant de calculer un indice d'adéquation de l'hôte est proposé. Cet indice permet une comparaison directe des impacts globaux et des potentiels reproducteurs des femelles de E. bryani attaquant des hôtes à différents stades.

     

HaNPV在宿主内的复制及其对宿主蛋白质代谢的影响

对棉铃虫Helicoverpaarmigera的中肠、血淋巴及脂肪体进行SDS-PAGE蛋白质分析表明：感染早期,HaNPV对棉铃虫的蛋白质合成有刺激作用,晚期则表现出抑制作用。感染96 h和120 h脂肪体有较高水平的多角体蛋白合成。电镜观察表明：①HaNPV感染棉铃虫除病毒在中肠复制后经出芽进入血腔感染脂肪体等组织外,还可能存在病毒粒子直接经中肠进入血腔而感染脂肪体这样的途径;②中肠与血腔之间存在屏障结构;③中肠不仅是一次感染时病毒粒子复制的场所,它完全可能被病毒粒子二次感染。在中肠细胞中没有发现多角体的形成。     

Survival of adults and developmental stages ofSarcoptes scabiei var.canis when off the host

All life-stages ofSarcoptes scabiei var.canis survive in the hosts' environment for several days to several weeks depending on r.h. and temperature. Survival of larvae was comparable to males; survival of nymphs was comparable to females. Females and nymphs generally survived longer than larvae and males.Low temperature (10–15°) and high r.h. prolonged survival of all life stages. At 10–15°C, females and nymphs survived 1–3 weeks at 97% r.h., 1–2 weeks at 75% r.h. and 5–8 days at 45% r.h. At 20–25°C, survival was significantly reduced but all life-stages survived at least 2 days at 25% r.h. and 5–6 days at 75–100% r.h. Long survival off the host coupled with host-seeking behavior of these mites make it likely that environmental contamination is a source of scabies in domestic and wild mammals, and in humans.     

Caste- and sex-specific adaptations within the olfactory pathway in the brain of the ant Camponotus floridanus

Olfaction plays a key role in mediating ant behavior, and ant societies are characterized by caste- and sex-specific division of labor. We propose that caste- and sex-specific adaptations in the olfactory pathway promote differences in olfactory behavior. This study compares olfactory centers in the brain of large (major) workers, small (minor) workers, virgin queens, and males of the carpenter ant Camponotus floridanus. The number of glomeruli in the antennal lobe was similar in the female castes, although the glomerular volumes differed. Males had approximately 45% fewer glomeruli compared to females (approximately 258 and approximately 434) and one antennal sensory tract was absent. A dual output pathway to the mushroom bodies was present in males. In contrast to females, however, the number of glomeruli connected to the medial antennocerebral tract was substantially smaller than those associated with the lateral tract. All glomeruli in the male antennal lobe contained serotonergic processes, whereas in the female castes glomeruli in the large tract six cluster lacked serotonergic innervations. We conclude that differences in general glomerular organization are subtle among the female castes, but sex-specific differences in the number, connectivity and neuromodulatory innervation of glomeruli are substantial and likely to underlie differences in olfactory processing and learning.     

Altered brain metabolism of testosterone is correlated with reproductive decline in aging quail

In aging quail, an increasing proportion of males show no sexual behavior. A decrease in the mean size of the tests, cloacal gland, and sternotracheal muscles is also observed. In both sexually active and inactive males, plasma testosterone decreases with age but more so in inactive birds. The behavioral and morphological changes observed during aging are correlated with shifts in the intracellular testosterone metabolism resulting in a change in the ratio of active versus inactive metabolites. In the hypothalamus there is a steady decrease with age of 5 beta-reductase activity in all birds and an increase in 5 alpha-reductase activity only in the birds which remain sexually active. In the cloacal gland, the 5 beta-reductase activity markedly increases with age but more so in the birds which become sexually inactive. These data support the notion that the effects of testosterone are controlled by enzymatic shifts which could modulate the sensitivity to the hormone at the cellular level.     

Performance of Myrmica ant colonies is correlated with the presence of social parasites

1. The performance of ant colonies depends on different factors such as nest site, colony structure or the presence of pathogens and social parasites. Myrmica ants host various types of social parasites, including the larvae of Maculinea butterflies and Microdonmyrmicae (Schönrogge) hoverfly. How these social parasites affect host colony performance is still unexplored. 2. It was examined how the presence of Maculinea teleius Bergsträsser, Maculinea alcon (Denis & Schiffermüller), and M. myrmicae larvae, representing different feeding and growth strategies inside host colonies, is associated with worker survival, the number of foragers, and colony productivity parameters such as growth and reproduction. 3. It was found that the presence of social parasites is negatively associated with total colony production and the production of ant larvae and gynes. Male production was lower only in nests infested by M. teleius, whereas the number of worker pupae was significantly higher in all types of infested colonies than in uninfested colonies. Laboratory observations indicated that nests infested by Maculinea larvae are characterised by a higher number of foragers compared to uninfested nests but we did not find differences in worker survival among nest types. 4. The observed pattern of social parasite influence on colony productivity can be explained by the feeding strategies of parasitic larvae. The most negative effect was found for M. teleius, which feeds on the largest host brood and eliminates a high number of sexual forms. The strong, adverse influence of all studied parasite species on gyne production may result in low queen production in Myrmica populations exposed to these social parasites.     

Intracellular cathepsin B activity is inversely correlated with the quality and developmental competence of bovine preimplantation embryos

Recently, the activity of cathepsins B was found to be correlated inversely with the developmental competence of bovine oocytes. In this study, we investigated (1) the role of intracellular cathepsin B expression and developmental competence as well as the quality of bovine preimplantation embryos, and (2) the effect of cathepsin B inhibitor (E-64) during in vitro culture (IVC) on the development and quality of bovine embryos. After in vitro fertilization (IVF) followed by IVC for 7 days, good and poor quality embryos classified by morphology and developmental rate on days 2, 4, and 7 were assessed for cathepsin B expression and activity. To investigate the effect of cathepsin B inhibition on embryonic development, putative zygotes were cultured with or without E-64, followed by evaluation of cleavage and blastocyst rates on days 2 and 7, respectively. Embryonic quality was evaluated by both TUNEL staining and total cell number in day-7 blastocysts. In each developmental stage, cathepsin B expression and activity were significantly higher in poor quality embryos than good quality ones. Moreover, addition of E-64 during IVC significantly increased both the blastocyst rate and the total cell number. TUNEL staining revealed that inhibition of cathepsin B significantly decreased the number of apoptotic nuclei in day-7 blastocysts. These results indicate that cathepsin B activity can be useful as a marker for inferior quality embryos. Moreover, inhibition of cathepsin B greatly improves the developmental competence of preimplantation embryos and increases the number of good quality embryos.     

Tissue Localization of the Endosymbiotic Bacterium “Candidatus Blochmannia floridanus” in Adults and Larvae of the Carpenter Ant Camponotus floridanus

The distribution of endosymbiotic bacteria in different tissues of queens, males, and workers of the carpenter ant Camponotus floridanus was investigated by light and electron microscopy and by in situ hybridization. A large number of bacteria could be detected in bacteriocytes within the midguts of workers, young virgin queens, and males. Large amounts of bacteria were also found in the oocytes of workers and queens. In contrast, bacteria were not present in oocyte-associated cells or in the spermathecae of mature queens, although occasionally a small number of bacteria could be detected in the testis follicles of males. Interestingly, the number of bacteriocytes in mature queens was strongly reduced and the bacteriocytes contained only very few or no bacteria at all, although the endosymbionts were present in huge amounts in the ovaries of the same animals. During embryogenesis of the deposited egg, the bacteria were concentrated in a ring of endodermal tissue destined to become the midgut in later developmental stages. However, during larval development, bacteria could also be detected in other tissues although to a lesser extent. Only in the last-instar larvae were bacteria found exclusively in the midgut tissue within typical bacteriocytes. Tetracycline and rifampin efficiently cleansed C. floridanus workers of their symbionts and the bacteriocytes of these animals still remained empty several months after treatment had ceased. Despite the lack of their endosymbionts, these adult animals were able to survive without any obvious negative effect under normal cultivation conditions.