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PubMed1977

Cytoplasmic bridges within the follicular epithelium of the ovarioles of two diptera, Aedes aegypti and Stomoxys calcitrans.

The cells of the follicular epithelium of the ovarioles of the mosquito, Aedes aegypti (L.), and of the stable fly, Stomoxys calcitrans (L.), have been found to be interconnected by cytoplasmic bridges. Cytoplasmic bridges have been reported between sibling gamete cells of both male and female insects, but these bridges have not been previously reported to exist between somatic cells of insects.

Aedes↗
PubMed1989

Phylogenetic diversity of cellular organization in the cardia of muscoid flies (Diptera: Schizophora).

In each of 30 dipteran species, representing 13 acalyptrate and 7 calyptrate families, the cardia is formed from specialized cells at the junction between foregut and midgut. Foregut epithelium forms the stomodeal valve; midgut epithelium envelops the valve to form the cardia's outer wall. Cytological characteristics within these epithelia differ from region to region and from species to species. Since the cardia secretes the peritrophic membrane, cardias with diverse patterns of cellular differentiation may be expected to produce peritrophic membranes with similarly diverse properties. Close relatives often share more details of cardia structure than do distantly related taxa. Within the monophyletic Calyptratae, a common pattern of cellular differentiation includes three distinct zones of columnar midgut cells enclosing a flanged stomodeal valve. Among species in the paraphyletic Acalyptratae, midgut typically includes a single zone of tall columnar cells, while the valve may be spheroidal, cylindrical, conical, or flanged. The correlation of phylogenetic distance with divergence in cardia organization implies a strong influence of ancestry upon current structure, regardless of current diet. However, at least some of the observed diversity in cardia structure is associated with dietary divergence. Calyptrate flies with derived blood-feeding behavior display cellular differentiation that is simplified from that seen in calyptrate relatives with less specialized feeding habits. This evolutionary modification suggests that cardia organization and hence peritrophic membrane structure can adapt to dietary changes, with possible significance for the spatial organization of digestive processes and interactions with ingested microorganisms.

Animals↗
PubMed1994

Structure and function of the frontal pit of Lipoptena spp. (Diptera: Hippoboscidae).

Scanning electron microscopy and histological techniques were used to study the structure and possible function of the frontal pit present in the frons of Lipoptena annalizeae. In the adult fly the opening leads into a closed sclerotized tube (torma) within a sclerite (fulcrum), to which the cibarial pump muscles are attached enabling the retraction of the proboscis. A method for softening the heads of Lipoptena for histological studies is also described.

Animals↗
PubMed1993

Spermatid nucleus of Megaselia scalaris Loew (Insecta, Diptera, Phoridae): a study using anti-histone antibodies, scanning electron microscopy, and a centromere-specific oligonucleotide.

The structure of elongated spermatid nuclei was examined in the fly Megaselia scalaris using indirect immunofluorescence with anti-histone antibodies, scanning electron microscopy, and in situ hybridization with a centromere-specific oligonucleotide. The immunofluorescence experiments showed that, in keeping with the situation in most animals, histones are hyperacetylated prior to their displacement from the nucleus in the course of spermiogenesis. Scanning electron microscopy revealed that grooves run parallel to the long axis of the spermatid nuclei. The chromatin is segmented into blocks lateral to the grooves. This finding most probably indicates that the chromatin is not yet maximally condensed at this stage. The retarded chromatin condensation may be correlated with the export of somatic histones from the nucleus. The location of the centromeres could not be identified using scanning electron microscopy, but in situ hybridization showed that a centromere-specific oligonucleotide mapped to the central or close to the central areas within the spermatid nucleus. Possibly, the chromosomes are extended and arranged parallel to the long axis of the spermatid nucleus.

Animals↗
PubMed2006

Effect of Bacillus thuringiensis subsp. israelensis and neonicotinoid insecticides on the fungus gnat Bradysia sp nr. coprophila (Lintner) (Diptera: Sciaridae).

The soil bacterium Bacillus thuringiensis Berliner subsp. israelensis (Bti), the neonicotinoid insecticides dinotefuran, imidacloprid, thiamethoxam and clothianidin and the insect growth regulator pyriproxyfen were evaluated to determine their efficacy against the larval stages of the fungus gnat Bradysia sp nr. coprophila (Lintner) in the laboratory. Treatments were applied as a drench to the growing medium in polypropylene deli containers. The Bti treatments had no effect on either instar tested, whereas all the other compounds negatively affected both the second and third instars. This study demonstrates that the soil bacterium B. thuringiensis var. israelensis may not be active on these larval stages, whereas the neonicotinoid insecticides and the insect growth regulator pyriproxyfen are effective on these stages. The fact that Bti is not effective on the second and third instars of the fungus gnat means that greenhouse producers using this insecticide must make applications before fungus gnat populations build up and before overlapping generations develop.

Animals↗
PubMed2006

Fumigant activity of plant essential oils and components from horseradish (Armoracia rusticana), anise (Pimpinella anisum) and garlic (Allium sativum) oils against Lycoriella ingenua (Diptera: Sciaridae).

Plant essential oils from 40 plant species were tested for their insecticidal activities against larvae of Lycoriella ingénue (Dufour) using a fumigation bioassay. Good insecticidal activity against larvae of L. ingenua was achieved with essential oils of Chenopodium ambrosioides L., Eucalyptus globulus Labill, Eucalyptus smithii RT Baker, horseradish, anise and garlic at 10 and 5 microL L(-1) air. Horseradish, anise and garlic oils showed the most potent insecticidal activities among the plant essential oils. At 1.25 microL L(-1), horseradish, anise and garlic oils caused 100, 93.3 and 13.3% mortality, but at 0.625 microL L(-1) air this decreased to 3.3, 0 and 0% respectively. Analysis by gas chromatography-mass spectrometry led to the identification of one major compound from horseradish, and three each from anise and garlic oils. These seven compounds and m-anisaldehyde and o-anisaldehyde, two positional isomers of p-anisaldehyde, were tested individually for their insecticidal activities against larvae of L. ingenua. Allyl isothiocyanate was the most toxic, followed by trans-anethole, diallyl disulfide and p-anisaldehyde with LC(50) values of 0.15, 0.20, 0.87 and 1.47 microL L(-1) respectively.

Animals↗
PubMed1997

Pathogenicity of axenic Steinernema feltiae, Xenorhabdus bovienii, and the bacto-helminthic complex to larvae of Tipula oleracea (Diptera) and Galleria mellonella (Lepidoptera).

The pathogenicity of the nematode-bacterium complex Steinernema feltiae-Xenorhabdus bovienii to larvae of Tipula oleracea and Galleria mellonella was investigated by injection of dauer juvenile nematodes carrying their bacterial symbiont cells (monoxenic nematodes). Axenic nematodes (free of bacteria) and the symbiotic bacteria themselves were tested. The LC50 of X. bovienii in T. oleracea was 15,700 colony forming units (CFU)/larva compared to < or = 8 CFU in G. mellonella. Xenorhabdus bovienii is apparently removed from the tipulids hemolymph, possibly by cellular defense mechanisms. Axenic nematodes were less pathogenic than monoxenic nematodes for both insects. The difference was less pronounced in G. mellonella larvae: one axenic nematode was sufficient to kill 80% in 1 day. The remaining insects found dead after 50 days were developmentally arrested. In T. oleracea 20 axenic nematodes caused 39% whereas 20 monoxenic dauer juveniles caused 90% mortality within 8 days. The data indicate that the virulence of the S. feltiae/X. bovienii complex is greater than the additive effect of the nematodes and their bacteria, further evidence for the synergistic activity of the symbiotic bacto-helminthic complex during pathogenesis.

Animals↗
PubMed1997

Phylogenetic analysis of North American Rhagoletis (Diptera: Tephritidae) and related genera using mitochondrial DNA sequence data.

Partial sequences (approximately 850 bp) of the mitochondrial 16S ribosomal RNA gene were determined for 21 members of the fruit fly genus Rhagoletis and 6 related tephritid taxa by sequencing DNA amplified by the polymerase chain reaction. Sequences were highly A + T rich, with an average G + C content of 19.2%. Sequence divergence ranged from 0 to 11.7% among the included taxa. Sequences were used to reconstruct the phylogeny of this group of flies with neighbor-joining and maximum parsimony methods. A group of 18 North American Rhagoletis species formed a monophyletic clade, and three morphologically based species groups were identified with strong statistical support. Relationships among the species groups were partially resolved. The tabellaria species group appears to be paraphyletic with respect to the pomonella species group, in contrast to previous allozyme analyses that united the cingulata and pomonella groups. The relations of the North American clade to other genera within the tribe Carpomyini were not clearly resolved. Rhagoletis striatella, a North American species that uses members of the tomato family (Solanaceae) as a larval host, may be more closely associated with South American Rhagoletis species and related genera than with the other North American Rhagoletis species.

Animals↗
PubMed1997

Molecular phylogenetic study of Tephritidae (Insecta: Diptera) using partial sequences of the mitochondrial 16S ribosomal DNA.

We analyzed sequence data from 925 base pairs within the mitochondrial 16S ribosomal DNA from 34 tephritid species and two outgroup taxa. DNA sequences were amplified by the polymerase chain reaction and sequenced by the dideoxy chain-termination method. Patterns of nucleotide composition and substitution were assessed based on sequence comparison. Phylogenetic relationships among the included taxa were inferred using neighbor-joining and maximum parsimony methods. The trees were congruent with the morphological classification and suggested the following phylogenetic relationships: (1) monophyly of the tribe Trypetini, s. str., excluding Parastenopa; (2) a possible sister group relationship between Platyparea and the subfamily Tephritinae; (3) a sister group relationship between Hexachaeta and the tribe Toxotrypanini; (4) monophyly of the Dacinae and possible relationship of Oedicarena to this subfamily; (5) monophyly of the tribe Adramini; and (6) the nonmonophyletic nature of the genus Rhagoletis. We propose that the 16S rDNA shows great promise for helping to create a phylogenetically based higher classification of the Tephritidae.

Animals↗
PubMed1997

Phylogeny of the genus Rhagoletis (Diptera: Tephritidae) inferred from DNA sequences of mitochondrial cytochrome oxidase II.

Despite a considerable literature describing the biology of flies in the tephritid genus Rhagoletis, the phylogenetic relationships of the more than 60 species classified within the genus are not well resolved. Knowledge of these relationships is important, not only in terms of obtaining information that will be useful for the control of Rhagoletis where it is an agricultural pest, but also in determining what role host plant shifts have played in the generation of Rhagoletis species diversity, a focal point in debate over the role of sympatric speciation in the evolutionary process. In this paper, the phylogenetic history of 28 Rhagoletis species and 6 species in related tephritid genera is inferred from nucleotide sequences of subunit II of the mitochondrial cytochrome oxidase (COII) gene and the adjacent tRNALeu/COII intergenic region. Analyses of the data using distance and character-state approaches suggest the following: (i) the genus Rhagoletis as currently defined is not monophyletic; (ii) the 5 predominantly North American Rhagoletis species groups do constitute a monophyletic assemblage; (iii) the North American species groups form 2 clades, 1 consisting of taxa in the R. pomonella and R. tabellaria species groups (plus R. fausta), and the other consisting of taxa in the R. ribicola, R. cingulata, and R. suavis species groups; and (iv) the origin(s) of the North American species groups is obscure, as evidenced by the recovery of clades containing both Palearctic and Neotropical taxa. Areas of congruence and conflict with published phylogenies of Rhagoletis are examined and, while many areas of conflict may be due to an insufficient number of characters or incomplete taxon sampling, we cannot discount the possibility that real differences exist between the Rhagoletis mitochondrial DNA gene tree and the Rhagoletis species tree.

Animals↗
PubMed2000

Utility of the mitochondrial cytochrome oxidase II gene for resolving relationships among black flies (Diptera: simuliidae).

The complete mitochondrial cytochrome oxidase II gene was sequenced from 17 black flies, representing 13 putative species, and used to infer phylogenetic relationships. A midge (Paratanytarsus sp.) and three mosquitoes (Aedes aegypti, Anopheles quadrimaculatus, and Culex quinquefasciatus) were used as outgroup taxa. All outgroup taxa were highly divergent from black flies. Phylogenetic trees based on weighted parsimony (a priori and a posteriori), maximum likelihood, and neighbor-joining (log-determinant distances) differed topologically, with deeper nodes being the least well-supported. All analyses supported current classification into species groups but relationships among those groups were poorly resolved. The majority of phylogenetic signal came from closely related sister taxa. The CO-II gene may be useful for exploring relationships at or below the subgeneric level, but is of questionable value at higher taxonomic levels. The weighting method employed gave phylogenetic results similar to those reported by other authors for other insect CO-II data sets. A best estimate of phylogenetic relationships based on the CO-II gene is presented and discussed in relation to current black fly classification.

Amino Acid Sequence↗
PubMed2000

Phylogeny of the scathophagidae (Diptera, calyptratae) based on mitochondrial DNA sequences.

The family Scathophagidae constitutes, together with members of the families Muscidae, Fannidae, and Anthomyiidae, the Muscoidea superfamily. The species Scathophaga stercoraria has been used extensively to investigate questions in animal ecology and evolution, particularly as a model system for studies of sperm competition and life history evolution. However, no phylogenetic studies have ever been performed on the Scathophagidae and the relationships within this family remain unclear. This study represents a molecular approach aimed at uncovering the phylogenetic relationships among 61 species representing 22 genera of Scathophagidae. A fragment of the terminal region of the mitochondrial gene COI (subunit I of the cytochrome oxidase gene) was sequenced in scathophagid species covering a wide geographic area, as well as a diverse spectrum of ecological habitats. Several clades grouping different genera and species have been identified, but the resolution power of the COI was insufficient to establish the exact relationships between these clades. The molecular data confirm the existence of a group consisting of the genera Delina, Chylizosoma, and Americina, which could represent the subfamily Delinae. Concerning the controversial position of the genus Phrosia, our data clearly suggest that it should be removed from the Delinae and placed within the genus Cordilura. Monophyly of most genera was confirmed, except for the genus Scathophaga, which should be divided into several different taxa.

Animals↗
PubMed2000

Molecular phylogenetics of the holly leafminers (Diptera: Agromyzidae: Phytomyza): species limits, speciation, and dietary specialization.

A molecular phylogenetic analysis was conducted to determine relationships and to investigate character evolution in the Phytomyza ilicis group of leafmining flies on hollies (Aquifoliaceae: Ilex). A total of 2207 bp of the mitochondrial cytochrome oxidase I and II genes were sequenced for all known holly leafminers, as well as for several undescribed members of this group. Maximum-parsimony analysis of the sequence data indicates that these leafminers form a monophyletic group with the inclusion of an undescribed leafminer that feeds on the distantly related plant Gelsemium sempevirens (Loganiaceae). Species boundaries of previously known and of undescribed holly leafmining species were confirmed with the molecular data, with one exception. Optimization of variable ecological and morphological characters onto the most parsimonious phylogeny suggests that these traits are evolutionarily labile, requiring multiple instances of convergence and/or reversal to explain their evolutionary history. Speciation in holly leafminers is associated with host shifts and appears to involve colonization of new hosts more often than cospeciation as the hosts diverge. Monophagy is the most common feeding pattern in holly leafminers, and more generalized feeding is inferred to have evolved at least two separate times, possibly as a prelude to speciation.

Animals↗