Persistence of antibiotic-resistant and -sensitive Proteus mirabilis strains in the digestive tract of the housefly (Musca domestica) and green bottle flies (Calliphoridae)

Synanthropic flies have been implicated in the rapid dissemination of antibiotic-resistant bacteria and resistance determinants in the biosphere. These flies stably harbor a considerable number of bacteria that exhibit resistance to various antibiotics, but the mechanisms underlying this phenomenon remain unclear. In this study, we investigated the persistence of antibiotic-resistant bacteria in the digestive tract of houseflies and green bottle flies, using Proteus mirabilis as a model microorganism. One resistant strain carried the blaTEM and aphA1 genes, and another carried a plasmid containing qnrD gene. Quantitative PCR and 454 pyrosequencing were used to monitor the relative abundance of the Proteus strains, as well as potential changes in the overall structure of the whole bacterial community incurred by the artificial induction of Proteus cultures. Both antibiotic-resistant and -sensitive P. mirabilis strains persisted in the fly digestive tract for at least 3 days, and there was no significant difference in the relative abundance of resistant and sensitive strains despite the lower growth rate of resistant strains when cultured in vitro. Therefore, conditions in the fly digestive tract may allow resistant strains to survive the competition with sensitive strains in the absence of antibiotic selective pressure. The composition of the fly-associated bacterial community changed over time, but the contribution of the artificially introduced P. mirabilis strains to these changes was not clear. In order to explain these changes, it will be necessary to obtain more information about bacterial interspecies antagonism in the fly digestive tract.     

Oviposition by screwworm flies (Diptera: Calliphoridae) on contact with host fluids

Factor affecting oviposition by screwworm flies, Cochliomyia hominivorax (Coquerel), contacting different host fluids were examined in a laboratory bioassay. Fresh bovine blood, which does not release the attractive odors involved in host finding, nevertheless stimulated as many or more females to oviposit than did the other fluids tested. These other fluids included attractive fluid from screwworm-infected wounds (a favored oviposition site in nature) and cultures of Providencia rettgeri (a bacterium implicated in attractant production). Oviposition did not vary with batch of fresh blood or frozen storage, making blood a useful standard for comparing oviposition rates among studies. Oviposition did vary with the substrate to which the blood was applied, suggesting that an interaction between tactile and chemical stimuli is important for host recognition. Both insemination and darkness during bioassay increased oviposition rates, but the magnitude of these effects was small compared with that due to substrate. Age had no effect for at least 1 wk after females became gravid.     

Seasonal population dynamics in Lucilia eximia (Wiedemann) (Diptera: Calliphoridae)

In this study the seasonal variation of fecundity, wing and tibia sizes were investigated in natural populations of Lucilia eximia (Wiedemann) as an attempt to determine the variations in life history of the species associated to seasonality. Specimens of L. eximia were monthly collected in Botucatu, S?o Paulo, Brazil, during two years and the adult females dissected to estimate fecundity. Body size was estimated by measuring wing and tibia. Fecundity and body size were seasonally analysed. A relatively constant temporal trajectory was found for fecundity, wing and tibia size over twenty-four months. Strong positive correlations between wing and tibia size, fecundity and wing and fecundity and tibia were observed. The maintenance of stable values in L. eximia indicates that it has suffered little seasonal influence over the period analysed. This result confirms the demographics and life history stable profile of the species in spite of seasonal climatic changes observed in the study area.     

Persistence of sterile screwworm (Diptera: Calliphoridae) flies at a release site.

Studies to determine the persistence of released, sterile screwworms, Cochliomyia hominivorax (Coquerel), were conducted in Belize, Central America, in 1987-1988. A total of nine releases were made, each consisting of 4,000 females marked with a fluorescent dust. Previous similar studies with baited fly traps indicated that flies died or dispersed from the release site within 3-4 d. For this study, flies were recaptured at sentinel animals. Recapture rates varied greatly between releases, a result that was not correlated with any weather parameter. The pattern of recapture indicated a sharp drop in the released population after 9-10 d, with a few flies persisting in the release area for up to 3 wk. The results suggest that survival of released sterile flies is comparable with estimated survival rate and life span of wild, native flies.     

Quality of transgenic laboratory strains of Cochliomyia hominivorax (Diptera: Calliphoridae)

Genetically modified, mass reared insects present novel possibilities for the future of insect control. One concern about manipulation of insects is a possible loss of strain quality due to the introduction of a foreign gene of any sort into the insect genome. Eight transgenic strains of screwworm, Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae), were compared with the wild-type parental laboratory strain in laboratory culture. Measurements of average fertility, fecundity, larval productivity, and longevity were analyzed. Two transgenic strains had significantly lower larval productivity than controls, one of which was explained by a homozygous lethal insertion of the transgene. Another strain produced significantly fewer eggs than controls. Overall strain characteristics, including measurements from egg, larva, pupa, and adult stages, were compared. Transgenic colonies did not consistently show significantly lower individual or aggregate strain quality characteristics than the control parental colony; hence, the presence of the transgene used to produce the strains tested did not incur a discrete cost to the colonies of laboratory-reared C. hominivorax.     

Gender-specific bacterial composition of black flies (Diptera: Simuliidae)

Although hematophagous black flies are well-known socioeconomic pests and vectors of disease agents, their associated bacteria are poorly known. A systematic analysis of the bacterial community associated with freshly emerged adult black flies of four North American species, using cultivation-independent molecular techniques, revealed 75 nonsingleton bacterial phylotypes. Although 17 cosmopolitan phylotypes were shared among host species, each fly species had a distinct bacterial profile. The bacterial composition, however, did not correlate strongly with the host phylogeny but differed between male and female flies of the same species from the same habitat, demonstrating that a group of insects have a gender-dependent bacterial community. In general, female flies harbor a less diverse bacterial community than do males. The anatomical locations of selected bacteria were revealed using fluorescence in situ hybridization. Understanding the physiological function of the associated bacterial community could provide clues for developing novel pest-management strategies.     

Postlarval fitness of transgenic strains of Cochliomyia hominivorax (Diptera: Calliphoridae)

Eight transgenic strains of Cochliomyia hominivorax (Coquerel) (Diptera: Calliphoridae) were compared with the wild-type parental laboratory strain (P95) in colony. Measurements of average weight of pupae, percentage of adults emerging from pupae, ratio of males to total emerged adults, and mating competitiveness were analyzed. The parental strain colony was subcultured and exposed to handling procedures equivalent to transgenic strains for valid comparison of overall colony fitness. None of the transgenic colonies exhibited significantly lower fitness characteristics than the control parental colony. One transgenic colony had a higher ratio of adults emerging from pupae, and five colonies had higher average pupal weight; because fitness cost would only be indicated by lower values, the statistical variations were not significant. Males of one transgenic strain were shown to mate with equal frequency compared with males of the parental strain. Hence, the presence of the transgene used to produce the strains tested did not incur a fitness cost to the colonies of laboratory-reared C. hominivorax.     

日本弓背蚁肠道细菌群落的季节特征

[目的]在长期的进化过程中,蚂蚁和微生物之间建立了复杂的联系,尤其肠道微生物对蚂蚁的食性进化和物种分化产生了巨大的影响.弓背蚁属Camponotus蚂蚁消化道内普遍存在内共生菌Blochmannia及其他肠道细菌,这些细菌在寄主蚂蚁营养补充方面发挥了重要的作用,此外肠道微生物对食物类型的变化十分敏感,这些信息可能有助于调查寄主蚂蚁在不同季节的取食习性.本研究旨在揭示弓背蚁属蚂蚁肠道微生物是否存在季节特征.[方法]采用16S rRNA-RFLP方法分析比较了了2个日本弓背蚁蚁巢(巢1和2)的工蚁在4个月份时间点(2012年6月12日,8月15日和10月10日,2013年4月15日)的肠道茵群组成.[结果]在8个样品中共发现了17个属的细菌和1种未知细菌,弓背蚁属蚂蚁特有的内共生茵Blochmannia是优势细菌,出现在所有样品中,占67.1％～98.8％;假单胞菌属Pseudomonas和肠杆菌属Enterobacter在大多数的样本中都检测到,其他属的细菌则零星分布在个别样品中,只占较低的比例.两个蚁巢工蚁肠道茵群在4个月份没有呈现一致的变化趋势,都具有低的细菌多样性.在巢1中,4月和10月的肠道细菌多样性相对较高,在6月和8月较低;而在巢2中,8月的肠道细菌多样性明显高于4,6和10月.两个蚁巢6月和10月的肠道茵群组成相似,但是8月和4月差异较大.[结论]日本弓背蚁两个蚁巢的工蚁肠道菌群组成和多样性都随季节产生变化,但是没有呈现一致的变化趋势,没有表现出明显的季节特征.     

Macrolarviparous reproduction in Ameniinae (Diptera: Calliphoridae)

Female flies of the subfamily Ameniinae were found by dissection to be macrolarviparous. The two ovaries each comprise two ovarioles, and a single egg passes at a time intoa large, muscular uterus, where it hatches and develops through the soft and rather featureless first larval instar. The larva moults in utero to a strongly spined, active second instar, with long, curved mandibular hooks and this stage is presumed to parasitize snails. Details are given of the larval morphology of Amenia and Paramenia spp., and the indications that these give about taxonomic affinities. The posterior spiracles are sunk in a deep pit, as is found amongst Sarcophagidae. It is concluded that on the basis of adult and larval characters the Ameniinae is a somewhat specialized group of flies, most closely related to Calliphoridae and with some affinity to Sarcophagidae.     

Life history responses to larval food shortages in four species of necrophagous flies (Diptera: Calliphoridae)

The effects of artificially reduced amounts of larval food on various life history parameters of Lucilia cuprina, Calliphora stygia, C. vicina, and C. hilli were measured to assess the likely reaction of these blowflies to competition in carrion. With increasing food shortage the puparia were reduced by up to 12% of the weight attained under conditions in which food was unlimited. The size of eggs laid by adults which had been subject to food deprivation as larvae was unchanged, but all species showed a reduction in the number of ovarioles. An index of mass-specific reproductive investment varied considerably between the species, and the relationships between this index and the preferred habitats and dispersal strategies of the species are discussed.     

Seasonal variations in bacterial communities in adirondack streams exhibiting pH gradients

Measurements of microbial biomass, bacterial numbers, and microbial production were determined for three small woodland streams located in the Adirondack Mountain region of New York State, USA. These streams exhibited spatial and temporal gradients in water pH ranging from a high of 7.0 to a low of 4.5. Twelve sites along these streams were used for comparative analyses of the effects of pH and related water chemistry parameters on the planktonic, sedimentary, and epilithic bacterial communities. The planktonic bacterial communities were not influenced by water pH or related water chemistry parameters. For sedimentary populations, the organic content of the sediment was more important than the chemistry of the overlying water. The epilithic bacterial communities, however, were influenced significantly by the pH of the water column, showing decreased bacterial production at lower pH.     

Growth energetics in relation to temperature for larvae of four species of necrophagous flies (Diptera: Calliphoridae)

The growth characteristics of the larvae of the major members of a necrophagous fly guild in Tasmania (Lucilia cuprina, Calliphora stygia, Calliphora vicina and Calliphora hilli) were measured to assess their competitive ability. The measurements were made at temperatures between 10 and 45°C, to cover the range of temperatures that would be encountered by larvae in carrion or myiasis under field conditions. The characteristics measured were net production and respiration. The indices K_2i (instantaneous growth efficiency), K_2c (cumulated growth efficiency) and M_i (instantaneous cost of maintenance) were calculated. Generally K_2c and K_2i are highest and M_i lowest at 25°C for all the species. A sinusoidal response in K_2c, K_2i and M_i against temperature is seen for L. cuprina, C. stygia and C. vicina. This response is‘cold’adapted in the Calliphora species and‘warm’adapted in L. cuprina. Egg size, egg caloric density and the energy content of the eggs are discussed in relation to the‘fitness’and reproductive strategies of the four species. The thermal tolerance range of L. cuprina determined here suggests that carrion may provide a significant number of this fly particularly in areas where Chrysomya spp. do not occur, and in large carcasses where temperatures are elevated.     

实蝇共生菌研究进展

实蝇类昆虫(双翅目Diptera:实蝇科Tephritidae)是重要的农业害虫,为害农作物茎秆和水果,严重影响农业生产和果蔬贸易,被许多国家列为重要的检疫性有害生物。实蝇共生菌对宿主实蝇的取食、生殖、发育及环境适应能力具有重要作用。目前,已有21个属的共生细菌(Enterobacter、Klebsiella、Citrobacter、Pseudomonas、Providencia、Erwinia、Acetobacter、Serratia、Proteus、Hafnia、Cedecea、Arthrobacter、Lactobacillus、Micrococcus、Streptococcus、Staphylococcus、Vibrio、Hafnia、Deinococcacea、Bacillus、Wolba-chia)以及1个属的共生真菌(Candida)被鉴定。其中,肺炎杆菌Klebsiella pneumoniae、产酸克雷伯氏菌Klebsiella oxytoca、成团泛菌Pantoea agglomerans、费氏柠檬酸杆菌Citrobter freundii、阴沟肠杆菌Enterobacter cloaca...     

A faunal survey of streblid flies (Diptera: Streblidae) associated with bats in Paraguay

An extensive survey of the ectoparasites infesting bats in Paraguay provides information regarding the taxonomy and host distribution of streblid bat flies at a geographic interface between subtropical and temperate habitats. Five families of bats representing 45 species, including Molossidae (5 genera and 15 species), Natalidae (1 genus and 1 species), Phyllostomidae (11 genera and 15 species), Noctilionidae (1 genus and 2 species), and Vespertilionidae (4 genera and 12 species) were collected from 24 localities across Paraguay and sampled for ectoparasites. In total, 2,467 bat flies were collected, representing 11 genera and 31 nominal species of Streblidae, of which 6 genera and 24 species are new records for Paraguay. No streblids were collected from vespertilionid bats; 23 species infested phyllostomids, 6 species noctilionids, 1 species a natalid, and 1 species molossids. Streblid bat flies were highly specific to certain host groups and individual host species, and their geographic distributions closely followed those of their host bats. Of 31 streblid species surveyed, 27 were monoxenous (i.e., associated with a single host species), and 4 were stenoxenous (i.e., associated with a group of phylogenetically related hosts). The number of streblid species is greatly reduced in the Chaco region west of the Paraguay River, largely because of the lack of phyllostomid host bats.     

C-banding and FISH in chromosomes of the blow flies Chrysomya megacephala and Chrysomya putoria (Diptera, Calliphoridae)

The blow flies Chrysomya putoria and C. megacephala have 2n=12 chromosomes, five metacentric pairs of autosomes and an XX/XY sex chromosome pair. There are no substantial differences in the karyotype morphology of these two species, except for the X chromosome which is subtelocentric in C. megacephala and metacentric in C. putoria and is about 1.4 times longer in C. putoria. All autosomes were characterized by the presence of a C band in the pericentromeric region; C. putoria also has an interstitial band in pair III. The sex chromosomes of both species were heterochromatic, except for a small region at the end of the long arm of the X chromosome. Ribosomal genes were detected in meiotic chromosomes by FISH and in both species the NOR was located on the sex chromosomes. These results confirm that C. putoria was the species introduced into Brazil in 1970s, and not C. chloropyga as formerly described.     

青藏高原丽蝇科昆虫物种多样性初探

本文从种数、特有物种和区系构成等角度分析了青藏高原丽蝇科昆虫的物种多样性。青藏高原已知丽蝇5亚科35属120种,占中国已知种数的44.28%,其中特有种55种,占该地区总种数的45.83%;区系构成以特有种、古北界 东洋界共同种及典型的东洋界种和古北界种为主,但澳洲界、新北界、非洲界和新热带界共同种也占一定比例。文中讨论了该地区特有种丰富的原因及地质历史环境对其的影响,分析了区系构成中各种区系成分的比例及形成原因。     

A detector dog for screwworms (Diptera: Calliphoridae)

A male German wirehaired pointer, Canis familiaris L., was trained to search for and locate screwworm, Cochliomyia hominivorax (Coquerel); pupae; and animals infested with screwworms. The command, "find it" led to the detection of a screwworm-infested animal and the command "search" led to the detection of screwworm pupae. After approximately 5 mo of training, the dog could detect screwworm-infested animals. After 3 mo more of training, the dog could detect screwworm pupae. Through 7 August 1989, the dog had a success rate of 100% (265 tests) with training dummies and 94.7% (18 successes for 19 tests) with screwworm-infested animals, for an overall success rate of 99.7% (285 successes for 286 tests). Use of detector dogs at quarantine stations could result in increased efficiency, economic savings, and decreased possibility of reintroduction of screwworms into eradicated areas.     

Seasonal abundance of horse flies (Diptera: Tabanidae) from two locations in eastern Croatia.

A total of 10,539 tabanid horse flies from 22 species and five genera was collected in the Tikves forest within the Kopacki rit Nature Park in eastern Croatia. Seasonal abundance was analyzed for the six most abundant species. Tabanus maculicornis, Tabanus tergestinus, and Haematopota pluvialis reached their highest peak abundance in the fourth week of June. Atylotus loewianus and Tabanus bromius reached their highest peak of abundance in the first week of August, whereas Tabanus sudeticus reached its maximum abundance in the third week of July. Horse flies also were collected once a week on the pasture at Petrijevci from mid-May to mid-September during 1993. Paired collections were made from a Malaise trap and from a horse by using a sweep net. A total of 2,867 tabanids belonging to 26 species was collected. The number of tabanids collected on horses was much higher than the total captured with Malaise traps. On their natural host (horse), 2.6 times more tabanids were collected than in the traps. Seasonal abundance was analyzed only for the eight most abundant species. Chrysops paralellogrammus, Tabanus autumnalis, Tabanus bromius, Tabanus tergestinus, Haematopota pluvialis, and Haematopota subcylindrica all reached their highest peak of abundance in the second week of July, whereas Tabanus maculicornis reached the maximal peak of abundance in the third week of June. Seasonal meteorological variability that occurs periodically from one year to another has a significant influence on the maximal peaks of tabanid abundance.