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PubMed2000

Higher-level phylogeny of the Therevidae (Diptera: insecta) based on 28S ribosomal and elongation factor-1 alpha gene sequences.

Therevidae (stilleto flies) are a little-known family of asiloid brachyceran Diptera (Insecta). Separate and combined phylogenetic analyses of 1200 bases of the 28S ribosomal DNA and 1100 bases of elongation factor-1alpha were used to infer phylogenetic relationships within the family. The position of the enigmatic taxon Apsilocephala Kröber is evaluated in light of the molecular evidence. In all analyses, molecular data strongly support the monophyly of Therevidae, excluding Apsilocephala, and the division of Therevidae into two main clades corresponding to a previous classification of the family into the subfamilies Phycinae and Therevinae. Despite strong support for some relationships within these groups, relationships at the base of the two main clades are weakly supported. Short branch lengths for Australasian clades at the base of the Therevinae may represent a rapid radiation of therevids in Australia.

Animals↗
PubMed2002

Speciation in the globeflower fly Chiastocheta spp. (Diptera: Anthomyiidae) in relation to host plant species, biogeography, and morphology.

Phylogenetic relationships among the Chiastocheta species (Diptera, Anthomyiidae) were investigated using a 1320-bp mitochondrial DNA fragment including parts of cytochrome oxidase subunits I and II. Larvae of the Chiastocheta genus feed exclusively on Trollius (Ranunculaceae) seeds. Six Chiastocheta species (and two vicariant taxa) coexist on Trollius europaeus in Europe, where they were shown to be the sole pollinator of their host plant. In Asia, several Trollius species are parasitized by Chiastocheta spp., and several other Trollius species are free of Chiastocheta. The plant-insect association is thus obligate in Europe but facultative in Asia. This system therefore provides a unique opportunity to study the evolution of an obligate mutualism between a plant and its seed parasite pollinators and its consequences on insect diversification. Most parsimonious, distance, and maximum likelihood analyses of 16 haplotypes from Europe and 14 from Asia show that European species do not form a monophyletic group. The species relationship indicated by egg morphology is only partly supported by molecular data. Moreover, a strong discrepancy between nucleotide variation and male genitalia morphology variation was found, particularly within and among European species coexisting on a single host plant. Molecular divergence across species ranges from 0 to 4.6%, suggesting a recent origin of the genus and several events of diversification, involving both host shifts and within-host-plant radiation. We discuss alternative evolutionary scenarios that are consistent with molecular data.

Animals↗
PubMed1983

Sexual dimorphism in the visual system of flies: the divided brain of male Bibionidae (Diptera).

The mapping of the compound eyes onto the visual neuropils and the cell types in the lamina and the lobula complex of Bibionidae (Diptera) were studied by means of extracellular cobalt injections and Golgi impregnations. Dorsal and ventral eyes in males map into separate dorsal-and ventral neuropils up to the level of the lobula complex. The dorsal-eye lamina is unilayered, while the ventral-eye lamina in males and the lamina in females are multilayered: layers A and C are invaded by en-passant terminals of long visual fibres, layer B by the terminals of short visual fibres. Long visual fibres have a short and a long terminal in the ventral medulla with terminal specialisations in three distinct layers. Only one type of receptor ending exists in the dorsal medulla, the terminal branches of which are restricted to one layer only. Arrays of contralateral neurones are found in the medial part of the dorsal lobula, which receives input from the zone of binocular vision of the ipsilateral dorsal eye, and in the posterior dorsal lobula and lobula plate. The dorsal lobula plate contains large tangential neurones, the dendritic arborisations of which are revealed by cobalt injection into the thoracic ganglia. The divided brain of male bibionids offers the opportunity to investigate separately the nervous systems involved in sex-specific visually guided flight behaviour and in 'general' visually guided flight control.

Animals↗
PubMed1994

The tympanal hearing organ of the parasitoid fly Ormia ochracea (Diptera, Tachinidae, Ormiini).

Tympanate hearing has evolved in at least 6 different orders of insects, but had not been reported until recently in the Diptera. This study presents a newly discovered tympanal hearing organ, in the parasitoid tachinid fly, Ormia ochracea. The hearing organ is described in terms of external and internal morphology, cellular organization of the sensory organ and preliminary neuroanatomy of the primary auditory afferents. The ear is located on the frontal face of the prothorax, directly behind the head capsule. Conspicuously visible are a pair of thin cuticular membranes specialized for audition, the prosternal tympanal membranes. Directly attached to these membranes, within the enlarged prosternal chamber, are a pair of auditory sensory organs, the bulbae acusticae. These sensory organs are unique among all auditory organs known so far because both are contained within an unpartitioned acoustic chamber. The prosternal chamber is connected to the outside by a pair of tracheae. The cellular anatomy of the fly's scolopophorous organ was investigated by light and electron microscopy. The bulba acustica is a typical chordotonal organ and it contains approximately 70 receptor cells. It is similar to other insect sensory organs associated with tympanal ears. The similarity of the cellular organization and tympanal morphology of the ormiine ear to the ears of other tympanate insects suggests that there are potent constraints in the design features of tympanal hearing organs, which must function to detect high frequency auditory signals over long distances. Each sensory organ is innervated by a branch of the frontal nerve of the fused thoracic ganglia. The primary auditory afferents project to each of the pro-, meso-, and metathoracic neuropils. The fly's hearing organ is sexually dimorphic, whereby the tympanal membranes are larger in females and the spiracles larger in males. The dimorphism presumably reflects differences in the acoustic behavior in the two sexes.

Animals↗
PubMed1982

Immunofluorescent characterization of DNA . RNA hybrids on polytene chromosomes of Trichosia pubescens (Diptera, sciaridae).

We have studied the distribution of DNA X RNA hybrids on polytene chromosomes with the aid of a goat antibody against DNA X RNA hybrids using the immunofluorescence technique. Fixed polytene chromosomes of the sciarid Trichosia pubescens (Diptera) show distinct, stage-specific labelling patterns throughout larval development. Controls for the staining procedure - including preincubation with hybrid-specific endoribonuclease H - prove that DNA X RNA hybrids are present on fixed chromosomes. They are revealed only under mild fixation conditions which do not efficiently immobilize all chromosomal proteins, indicating that some proteins have to be removed to make the antigens accessible to antibody. Certain fixation conditions may also cause local denaturation of chromosomal DNA, and some hybrids may possibly form during specimen preparation. After incorporation of radioactive uridine, a combination of phase contrast, fluorescent, and autoradiographic images of one and the same chromosomal preparation demonstrates that hybrid fluorescence is confined to transcriptionally active regions. Two puff classes can be distinguished. The first binds antibody and includes most RNA puffs and all DNA puffs so far studied; the second, comprising some RNA puffs, does not show bright fluorescence in spite of the fact that RNA synthesis is high as revealed by 3H-uridine incorporation. DNA X RNA hybrids are not found at DNA puff sites during the DNA amplification period; these sites contain detectable hybrids only when transcription is taking place. - Combination of the fluorescent technique with its excellent resolution and autoradiography should be helpful in studying detailed topological aspects of transcriptionally active chromosomal regions.

Animals↗
PubMed1995

Genome reorganization from polyteny to polyploidy in the nurse cells found in onion fly (Delia antiqua) and cabbage root fly (Delia radicum) ovaries (Diptera, Anthomyiidae).

The material required to ensure successful embryogenesis in the onion fly (Delia antiqua) and the cabbage root fly (Delia radicum) (Diptera, Anthomyiidae) is supplied by 15 nurse cells, while the oocyte chromosomes enter a quiescent stage during prophase I of meiosis. This level of transcription is achieved by the polyploidization of the nurse cell DNA. Elongate polytene chromosomes form in both species, but lack the banding and conspicuous puffing commonly seen in other dipteran tissues. The polytene chromosomes contract until they finally appear as small, densely staining spheres. These fragment into large numbers of endochromosomes that are much smaller than their mitotic counterparts, which then despiralize, resulting in the flocculate appearance of the nurse cell nucleus. Photodensitometry revealed a gradient of DNA values between nurse cells near the oocytes and those further away. Final DNA values 1000 times the haploid level were recorded in the nurse cell nearest to the oocyte compared with 336 times the C-value in the most distal cell. At lower temperatures (< 10 degrees C), the polytene chromosomes become banded and longer. None of the onion flies kept in these conditions produced viable eggs, though there was some reproductive success among the cabbage root flies.

Animals↗
PubMed1980

5-methylcytosine in the DNA of the polytene chromosomes of the diptera Sciara coprophila, Drosophila melanogaster and D. persimilis.

5-Methylcytosine has been detected in the DNA of the polytene chromosomes of Sciara coprophila, Drosophila melanogaster and D. persimilis, using specifically purified antibodies to 5-methylcytidine. The 5-methylcytosine is present in GC-rich sequences in the bands. Virtually no 5-methylcytosine is detectable in mitotic metaphase chromosomes of S. coprophila. Thus, methylation is associated with polytenization in these diptera. Restriction enzyme studies using HpaII, MspI, HhaI and AluI indicate that unmethylated 5'-CCGG-3', 5'-GCGC-3' and 5'-AGCT-3' sequences are abundant in polytene chromosome DNA. These sequences are probably not major sites of methylation. Since the DNA in the bands of polytene chromosomes is generally transcriptionally inactive, as well as extensively methylated, these results are consistent with the hypothesis that genes in the bands have been inactivated by a process involving DNA methylation.

5-Methylcytosine↗
PubMed1984

Molecular evolution in Drosophila and the higher Diptera II. A time scale for fly evolution.

In this paper, we examine first the steadiness of the rate of evolutionary change in a larval hemolymph protein, LHP, in numerous Drosophila species. We estimated amino acid sequence divergence from immunological distances measured with the quantitative microcomplement fixation technique. Using tests not depending on knowledge of absolute times of divergence, we estimated the variance of the rate of evolutionary change to be at least 4 times as large as that for a process resembling radioactive decay. Thus, the rate of evolution of this protein is as uniform as that of vertebrate proteins. Our analysis indicates no acceleration of protein evolution in the lineages leading to Hawaiian drosophilines. Second, we give an explicit description of a procedure for calculating the absolute value of the mean rate of evolutionary change in this protein. This procedure is suggested for general use in calculating absolute rates of molecular evolution. The mean rate of evolution of LHP is about 1.2 immunological distance units per million years, which probably corresponds to a unit evolutionary period of 4 million years; LHP thus evolves at a rate comparable to that of mammalian hemoglobins. Finally, we utilize the calibrated rate of LHP evolution to derive a time scale of evolution in the Drosophilidae and higher Diptera.

Animals↗
PubMed2003

Changes in amount of bacteria during gut passage of leaf litter and during coprophagy in three species of Bibionidae (Diptera) larvae.

To elucidate the interaction between bacteria and saprophagous Diptera larvae, the amounts of bacteria in leaf litter, individual gut compartments, and feces of three species of Bibionidae (Bibio pomonae, Bibio marci, and Penthetria holosericea), feeding either directly on leaf litter or on fecal pellets produced from leaf litter by larvae of the same species, were assessed by determining total direct counts and viable counts on solid media at different pH. In P. holosericea, the effect of various cultivation temperatures on direct counts of bacteria in individual compartments was also demonstrated. In all species, the amount of bacteria in the anterior mesenteron was lower than in the consumed food, regardless of whether the larvae were feeding on leaf litter or feces, and increased again in the posterior part of the gut. The amount of bacteria in these compartments was generally higher in larvae feeding on feces than in those feeding on leaf litter, whereas the amount of bacteria found in the ceca varied. In B. marci, the amount of bacteria in the mesenteron sections able to grow on alkaline medium (pH 9) was higher than that of bacteria able to grow on slightly acidic medium (pH 5.5) during both the first and the second gut passage. In B. pomonae and P. holosericea, this increase was observed only during the second gut passage. The effect of gut passage in P. holosericea on changes in direct counts of bacteria was more pronounced when the larvae were fed at 5 degrees C as compared to 20 degrees C. Radiolabeled bacteria were digested in the gut and utilized as a source of energy and nutrients by the larvae; digested bacteria represented up to 10% of the material assimilated by the larvae. Lysozyme activity in whole-gut extracts of P. holosericea had a pH optimum of at pH 7, indicating a low in situ activity in the alkaline mesenteron. Proteinase activity, however, had an optimum at pH > 12, suggesting that the digestion of bacteria in the bibionid gut is caused by a combination of digestive proteinases and alkaline pH in the anterior mesenteron.

Animals↗
PubMed2002

The major yolk proteins of higher Diptera are homologs of a class of minor yolk proteins in lepidoptera.

In most oviparous animals, including insects, vitellogenin (Vg) is the major yolk protein precursor. However, in the higher Diptera (cyclorrhaphan flies), a class of proteins homologous to lipoprotein lipases called yolk polypeptides (YP) are accumulated by oocytes instead of Vg, which is not produced at all. Lepidopterans (moths) produce Vg as the major yolk protein precursor, but also manufacture a class of minor yolk proteins referred to as egg-specific proteins (ESP) or YP2s. Although the lepidopteran ESP/YP2s are related to lipoprotein lipases, previous attempts to directly demonstrate their homology with higher-dipteran YPs were unsuccessful. In this paper, a multiple alignment of amino acid sequences was constructed using a shared lipid binding motif as an anchor, to demonstrate that lepidopteran ESP/YP2s, higher-dipteran YPs, and lipoprotein lipases are indeed homologous. Phylogenetic analyses of the aligned sequences were performed using both distance-based and parsimony strategies. It is apparent that the higher dipterans did not requisition a lipoprotein lipase to replace Vg as a yolk protein precursor, but instead utilize a class of proteins with an evolutionary history of use as minor constituents of yolk in other insects.

Amino Acid Sequence↗
PubMed2006

Bacteria isolated from the different developmental stages and larval organs of the obligate parasitic fly, Wohlfahrtia magnifica (Diptera: Sarcophagidae).

Wohlfahrtia magnifica (Diptera: Sarcophagidae) is the major myiasis-causing fly species in the whole of Eurasia for most important domestic animals. The aim of the present work was to obtain data on the culturable bacteria isolated under aerobic conditions from this fly: bacteria were isolated from all developmental stages (larvae, pupa, and imago) of Wohlfahrtia magnifica, and the third-stage larval organs were also sampled. To determine the possible antagonistic effects between the dominant bacterial groups, an antibiosis assay was carried out. Plating and isolation of bacteria was performed by classical microbiological methods. Characterization of the isolated strains was carried out via a polyphasic approach; classical phenotypic tests, chemotaxonomical examinations, and 16S rDNA sequence analyses were also applied. In the case of maggot macerate samples, members of the family Enterobacteriaceae were characteristic. Members of a new genus (Schineria) belonging to the gamma subdivision of proteobacteria were also isolated. According to our data, the shifts in the Schineria and Proteus populations within the larvae are strongly influenced by their interactions with each other and among the members of the family Enterobacteriaceae. The pupa and imago samples contained several other Gram-negative bacteria (Stenotrophomonas, Brevundimonas, etc.). Among Gram-positive bacteria, in all maggot macerate samples, members of the genus Bacillus and the Arthrobacter-Micrococcus group of actinobacteria were dominant (neither of them was a producer or sensitive to the compounds of other microorganisms), and bacteria related to the genus Corynebacterium were also found. From the larvae Aureobacterium liquefaciens and Enterococcus faecalis were isolated, and from the pupae Dietzia maris and Enterococcus faecalis. In the samples of third-stage larval organs, the dominant groups were the same as in the third-stage larval macerate sample; however, several additional genera/species were observed (Rhodococcus fascians, Streptomyces sp., Rathayibacter sp., Bacillus thuringiensis/cereus).

Animal Structures↗
PubMed2001

Isolation and identification of bacteria associated with adult laboratory Mexican fruit flies, Anastrepha ludens (Diptera: Tephritidae).

From the guts of new and old colonies (female and male) of Mexican fruit flies, Anastrepha ludens (Diptera: Tephritidae), we identified a total of 18 different bacterial species belonging to the family Enterobacteriaceae, Pseudomonadaceae, Vibrionaceae, Micrococcaceae, Deinococcacea, Bacillaceae, and the genus Listeria. Enterobacter, Providencia, Serratia, and Staphylococcus spp. were the most frequently isolated genera, with Citrobacter, Streptococcus, Aerococcus, and Listeria found less frequently. We found Bacillus cereus, Enterobacter sakazakii, Providencia stuartii, and Pseudomonas aeruginosa only in the new colony, Aeromonas hydrophila and Klebsiella pneumoniae spp. pneumoniae only in the old colony. We also studied resistance/sensitivity to 12 antibiotics for six bacterial isolates such as Enterobacter cloacae, E. sakazakii, K. pneumoniae spp., Providencia rettgeri, P. aeruginosa, and Bacillus cereus. Isolates on the whole were resistant to penicillin and ampicillin (five of six isolates) and sensitive to rifampin and streptomycin (six of six isolates). Antibiotic resistance profiles might be useful characteristics for distinguishing among species and strains of these bacteria, probably having ecological significance with respect to intra- and inter-specific competition within host cadavers, and could have implications for the utility of these organisms for biological control, including the alternative control strategy, paratransgenesis.

Animals↗
PubMed2000

Correlation of the insecticidal activity of the Bacillus thuringiensis A4 strain against Bactrocera oleae (Diptera) with the 140-kDa crystal polypeptide.

The crystals of the soil-isolated Bacillus thuringiensis (Bt) strain A4 consist of two polypeptides with molecular mass of 140 kDa and 32 kDa that exhibit insecticidal activity against adult flies of Bactrocera oleae (Diptera). Plasmid curing applied to this strain resulted in the isolation of several subclones exhibiting alterations in their crystal polypeptides as well as two acrystalliferous subclones. The crystals of subclone 1.1 lacked the 32-kDa polypeptide and consisted uniquely of a 140-kDa polypeptide antigenically related to the parental 140-kDa crystal polypeptide. Additionally, the crystals of this subclone exhibited insecticidal activity against B. oleae equivalent to that of the parental strain. Therefore, the 32-kDa crystal polypeptide is dispensable for insecticidal activity, which appears to be dependent on the presence of the 140-kDa crystal polypeptide.

Animals↗
PubMed2000

Optic flow representation in the optic lobes of Diptera: modeling innervation matrices onto collators and their evolutionary implications.

A network model of optic flow processing, based on physiological and anatomical features of motion-processing neurons, is used to investigate the role of small-field motion detectors emulating T5 cells in producing optic flow selective properties in wide-field collator neurons. The imposition of different connectivities can mimic variations observed in comparative studies of lobula plate architecture across the Diptera. The results identify two features that are crucial for optic flow selectivity: the broadness of the spatial patterns of synaptic connections from motion detectors to collators, and the relative contributions of excitatory and inhibitory synaptic outputs. If these two aspects of the innervation matrix are balanced appropriately, the network's sensitivity to perturbations in physiological properties of the small-field motion detectors is dramatically reduced, suggesting that sensory systems can evolve robust mechanisms that do not rely upon precise control of network parameters. These results also suggest that alternative lobula plate architectures observed in insects are consistent in allowing optic flow selective properties in wide-field neurons. The implications for the evolution of optic flow selective neurons are discussed.

Adaptation, Physiological↗
PubMed2002

The blowfly Chrysomya albiceps (Wiedemann) (Diptera: Calliphoridae) as a new forensic indicator in Central Europe.

During the summer months of the year 2001, six forensic cases (one is reported in the present paper), a pig carrion study in the city of Vienna (latitude 48 degrees 12'N, longitude 16 degrees 22'E) and several liver-baited traps north of Vienna, yielded large numbers of maggots of the blowfly Chrysomya albiceps (Wiedemann) (Diptera: Calliphoridae). Apart from some records from France, reports of C. albiceps from the palearctic region north of the Alps (i.e. north of a latitude of 48 degrees N) have been scarce. Our findings provided an opportunity to derive developmental schedules for C. albiceps at five different constant temperatures (15, 20, 25, 30, 35 degrees C). The minimal duration of development from oviposition to adult was inversely related to temperature, ranging from 8.3 +/- 0.5 days at 35 degrees C to 19.2 +/- 0.92 days at 20 degrees C. Although eggs hatched after 1.9 +/- 0.16 days at 15 degrees C, larvae did not complete development and frequently died during the first instar stage. We also found a high mortality rate (up to 99%) of native L. sericata larvae caused by predation of C. albiceps larvae under laboratory conditions, indicating a high susceptibility of L. sericata to attack by C. albiceps. Apart from this, the current and possible future distribution of C. albicepsin Europe is discussed. The northward expansion of its range beyond southern Europe obviously decreases the value of C. albiceps in estimating the site of death, in that it is no longer exclusive to southern European regions. Moreover, the aggressive feeding behaviour of second and third instar larve of C. albiceps could reset the post-mortem insect clock by clearing a corpse of all earlier arrivers.

Animals↗
PubMed2003

Extraction of gunshot residues from the larvae of the forensically important blowfly Calliphora dubia (Macquart) (Diptera: Calliphoridae).

Whole body concentrations of lead (Pb), barium (Ba) and antimony (Sb) were determined in larvae of the blowfly Calliphora dubia (Macquart) (Diptera: Calliphoridae) removed from a piece of beef shot and contaminated with gunshot residue and compared with the concentrations detected within larvae feeding on a control piece of beef. Whole larvae were taken into solution and analysed using inductively coupled plasma-mass spectrometry (ICP-MS). Significantly higher concentrations of Pb, Ba and Sb were detected within the larvae feeding on the shot piece of beef compared with larvae that were feeding on the control piece of beef. Initial results indicate that the concentrations of Pb and Sb within the larvae decrease as the duration of feeding increases, whereas Ba concentrations appear to increase, suggesting a bioaccumulation of Ba within the larvae. The second part of this experiment investigated the depuration of Pb, Ba and Sb from the larvae following removal of the gunshot residue source. A significant reduction in Pb, Ba and Sb concentrations within the larvae was observed following the transfer of larvae from the shot piece of beef to the control piece of beef.

Animals↗
PubMed2004

Toxicological data and growth characteristics of single post-feeding larvae and puparia of Calliphora vicina (Diptera: Calliphoridae) obtained from a controlled nordiazepam study.

Larvae of the Calliphora vicina (Diptera: Calliphoridae) were reared on artificial food spiked with different concentrations of nordiazepam. The dynamics of the accumulation and conversion of nordiazepam to its metabolite oxazepam in post-feeding larvae and empty puparia were studied. Analysis was performed using a previously developed liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. This method enabled the detection and quantitation of nordiazepam and oxazepam in single larvae and puparia. Both drugs could be detected in post-feeding larvae and empty puparia. In addition, the influence of nordiazepam on the development and growth of post-feeding larvae was studied. However, no major differences were observed for these parameters between the larvae fed on food containing nordiazepam and the control group. To our knowledge, this is the first report describing the presence of nordiazepam and its metabolite, oxazepam, in single Calliphora vicina larvae and puparia.

Animals↗
PubMed2004

Genetic identification of forensically important flesh flies (Diptera: Sarcophagidae).

Unequivocal identification of fly specimens is an essential requirement in forensic entomology. However, not all species can be determined at every developmental stage, which is illustrated by the flesh flies (Diptera: Sarcophagidae), important members of the necrophagous insect fauna. Up to now no suitable key for the identification of the immature stages of this family of flies exists. DNA analysis of selected mitochondrial genes was applied to solve this problem. Sequence data of selected regions of the CO I and ND 5 genes of the most important European flesh fly taxa associated with cadavers are presented, which can act as reference standards for species determination.

Animals↗