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PubMed2003

Molecular evolutionary convergence of the flight muscle protein arthrin in Diptera and hemiptera.

Uniquely, the asynchronous flight muscle myofibrils of many insects contain arthrin, a stable 1:1 conjugate between actin and ubiquitin. The function of arthrin is still unknown. Here we survey for the presence of arthrin in 63 species of insect across nine orders using Western blotting. Analysis of the evolutionary distribution shows that arthrin has evolved a limited number of times but at least once in the Diptera and once in the Hemiptera. However, the presence of arthrin does not correlate with any observed common features of flight mechanism, natural history, or morphology. We also identify the site of the isopeptide bond in arthrin from Drosophila melanogaster (Diptera) and Lethocerus griseus (Hemiptera) using mass spectrometry. In both species, the isopeptide bond is formed between lysine 118 of the actin and the C-terminal glycine 76 of ubiquitin. Thus, not only the ubiquitination of actin but also the site of the isopeptide bond has evolved convergently in Diptera and Hemiptera. In terms of the actin monomer, lysine 118 is near neither the binding sites of the major actin-binding proteins, myosin, tropomyosin, or the troponins, nor the actin polymerization sites. However, molecular modeling supports the idea that ubiquitin bound to an actin in one F-actin strand might be able to interact with tropomyosin bound to the actin monomers of the other strand and thereby interfere with thin filament regulation.

Actins↗
PubMed1997

An episodic change of rDNA nucleotide substitution rate has occurred during the emergence of the insect order Diptera.

We have studied the potential reasons for a conspicuous deviation of substitution rates in Dipteran ribosomal genes. Systematic pairwise relative-rate tests reveal that a significant increase in substitution rate is characteristic for Diptera, but not for the other insects analyzed. Estimation of sequence change in specific lineages reveals that most of these substitutions took place during the evolution of the Dipteran stem lineage. When related to the paleontologically documented periods of absolute time, the substitution rate in the stem lineage of the Diptera underwent an at least 20-fold increase compared to other insect groups and subsequently dropped by a factor of 10 before the diversification of the major Dipteran subgroups. Systematic comparisons of nucleotide composition show that this episodic change in substitution rate was accompanied by a significant increase in A+T content of Dipteran rDNA. Our data suggest that the episodic evolution of the Dipteran rDNA has most probably been caused by a change of directional mutation pressure which must have occurred during the evolution of the stem lineage of the Diptera.

Animals↗
PubMed1997

Conservation of hexamerin endocytosis in Diptera.

In cyclorrhaphan Diptera at least two different types of haemolymph proteins exist which belong to the class of hexamerins. In the last larval instar of Calliphora vicina, the highly aromatic hexamerin, arylphorin, and the second hexamerin, PII, make up about 90% of haemolymph proteins. Both of these proteins are selectively taken up by the fat body cells at the end of larval life and share a common membrane-bound receptor. In addition, hexamerins and possible hexamerin receptors of Calliphora vicina, Calliphora vomitoria, Drosophila melanogaster, Ceratitis capitata, Sarcophaga bullata, Musca domestica and Protophormia terraenovae were investigated. Uptake of arylphorin by the larval fat bodies of Calliphora vicina as well asarylphorin-receptor binding can be competed in vitro by haemolymph from other Diptera. Therefore, hexamerin-receptor binding must be conserved among related cyclorrhaphan Diptera and between different types of hexamerins within a species. As the degree of competition is in good agreement with the presumed phylogenetic distances between these species, the method described here provides a simple tool to estimate evolutionary distances.

Animals↗
PubMedDate not supplied

The evolution of abdominal reduction and the recent origin of distinct Abdominal-B transcript classes in Diptera.

In insects, the Hox gene Abdominal-B (Abd-B) governs the development of the posterior-most segments, the number and fate of which differ within and between orders. A striking feature of insect evolution is a trend toward the reduction of posterior abdominal segments which is most pronounced in higher Diptera. In Drosophila melanogaster, two distinct Abd-B transcript classes and protein isoforms are expressed in non-overlapping domains and have discrete functions in patterning the posterior abdomen. It has been proposed that evolutionary changes in Abd-B structure and expression are responsible for the reduction of the dipteran abdomen. We have investigated the relationship between the evolution of the Abd-B gene and abdominal reduction by analyzing the structure and expression of homologs from four additional dipterans representing distinct clades within the order. The lower dipteran mosquito Anopheles gambiae expresses a single Abd-B transcript class, as do two species phylogenetically intermediate to mosquitoes and drosophilids. These results delimit the evolution of distinct functional Abd-B isoforms to within the dipteran radiation after the origin of the reduced abdominal morphology. Furthermore, we found that the spatial distribution of Abd-B transcripts in non-drosophilid Diptera is identical to the combined domains of the two D. melanogaster Abd-B transcripts. Therefore, neither the structural evolution nor changes in the spatial regulation of Abd-B account for the derived abdomen of higher Diptera. The recent subfunctionalization of this Hox gene has occurred without any apparent morphological correlate. We conclude that regulatory modifications to developmental programs downstream of or parallel to Abd-B are responsible for the evolutionary reduction of the higher dipteran postabdomen.

Abdomen↗
PubMed1999

The development and evolution of bristle patterns in Diptera.

The spatial distribution of sensory bristles on the notum of different species of Diptera is compared. Species displaying ancestral features have a simple organization of randomly distributed, but uniformly spaced, bristles, whereas species thought to be more derived bear patterns in which the bristles are aligned into longitudinal rows. The number of rows of large bristles on the scutum was probably restricted to four early on in the evolution of cyclorraphous Brachyceran flies. Most species have stereotyped patterns based on modifications of these four rows. The possible constraints placed upon the patterning mechanisms due to growth and moulting within the Diptera are discussed, as well as within hemimetabolous insects. The holometabolic life cycle and the setting aside of groups of imaginal cells whose function is not required during the growth period, may have provided the freedom necessary for the evolution of elaborate bristle patterns. We briefly review the current state of knowledge concerning the complex genetic pathways regulating achaete-scute gene expression and bristle pattern in Drosophila melanogaster, and consider mechanisms for the genetic regulation of the bristle patterns of other species of Diptera.

Animals↗
PubMed2004

Conservation of capa peptide-induced nitric oxide signalling in Diptera.

In D. melanogaster Malpighian (renal) tubules, the capa peptides stimulate production of nitric oxide (NO) and guanosine 3', 5'-cyclic monophosphate (cGMP), resulting in increased fluid transport. The roles of NO synthase (NOS), NO and cGMP in capa peptide signalling were tested in several other insect species of medical relevance within the Diptera (Aedes aegypti, Anopheles stephensi and Glossina morsitans) and in one orthopteran out-group, Schistocerca gregaria. NOS immunoreactivity was detectable by immunocytochemistry in tubules from all species studied. D. melanogaster, A. aegypti and A. stephensi express NOS in only principal cells, whereas G. morsitans and S. gregaria show more general NOS expression in the tubule. Measurement of associated NOS activity (NADPH diaphorase) shows that both D. melanogaster capa-1 and the two capa peptides encoded in the A. gambiae genome, QGLVPFPRVamide (AngCAPA-QGL) and GPTVGLFAFPRVamide (AngCAPA-GPT), all stimulate NOS activity in D. melanogaster, A. aegypti, A. stephensi and G. morsitans tubules but not in S. gregaria. Furthermore, capa-stimulated NOS activity in all the Diptera was inhibited by the NOS inhibitor l-NAME. All capa peptides stimulate an increase in cGMP content across the dipteran species, but not in the orthopteran S. gregaria. Similarly, all capa peptides tested stimulate fluid secretion in D. melanogaster, A. aegypti, A. stephensi and G. morsitans tubules but are either without effect or are inhibitory on S. gregaria. Consistent with these results, the Drosophila capa receptor was shown to be expressed in Drosophila tubules, and its closest Anopheles homologue was shown to be expressed in Anopheles tubules. Thus, we provide the first demonstration of physiological roles for two putative A. gambiae neuropeptides. We also demonstrate neuropeptide modulation of fluid secretion in tsetse tubule for the first time. Finally, we show the generality of capa peptide action, to stimulate NO/cGMP signalling and increase fluid transport, across the Diptera, but not in the more primitive Orthoptera.

Amino Acid Sequence↗
PubMedDate not supplied

Aneuploid and polyploid cellular DNA heterogeneity in insect cell material of diptera species analyzed by flow cytometry.

Flow cytometric 1-parameter DNA analysis and 2-parameter DNA/protein analysis have been performed with cell material of the diptera species Chironomus thummi, Drosophila melanogaster, Calliphora vicina and Musca domestica using an impulse cytophotometer with a new quartz objective, that was especially manufactured for cytofluorometric investigations. The occurrence of heterogenous cell populations with aneuploid and polyploid DNA content within the cell material of different developmental stages of diptera species have been determined, whereby in larvae polyploid cell populations and in imagos aneuploid cell populations predominate. Partially separation of 2 C cells from other cell populations with higher DNA content can be done by Ficoll-Hypaque centrifugation as demonstrated with cell material from Chironomus larvae. For flow cytometric DNA analysis of insect cell material a simple and rapid cell preparation and staining technique is presented by using the DNA-specific fluorochrome DAPI in combination with the protein fluorochrome sulforhodamine 101. Employment of flow cytometry in diptera genetics might be a new tool for cytological and cytogenetic investigations as shown with the classical genetic objects Chironomus and Drosophila.

Aneuploidy↗
PubMed2003

Diptera of sanitary importance associated with composting of biosolids in Argentina.

OBJECTIVE: Odorous compounds produced at the biosolids composting plant in Bariloche (NW Patagonia) attract a variety of insects, mainly belonging to the order Diptera. In order to characterize these flies, collected specimens were taxonomically identified, their community characteristics were described and their sanitary and synanthropic importance and autochthonous or introduced character were determined. METHODS: Sampling was performed from October 1999 until March 2000. Adults were collected using an entomological net, and larvae and puparia were obtained from the composting material and incubated to obtain adults. Richness, abundance and sex ratio were calculated. RESULTS: A total of 9 taxa of Diptera were identified: Sarconesia chlorogaster, Phaenicia sericata, Calliphora vicina, Cochliomya macellaria, Ophyra sp, Muscina stabulans, Musca domestica, Sarcophaga sp and Fannia sp. Specimens of Anthomyiidae, Acaliptratae and one larva of Eristalis tenax were also found. Ophyra sp. was the most abundant taxa. All the captured Diptera belonged to introduced taxa. Most of them are considered to be eusynanthropic and/or hemisynanthropic and have sanitary importance as they may cause myiasis and pseudomyiasis. The high number of females registered and the finding of immature stages indicated that flies can develop their complete life cycle on biosolid composting windrows. CONCLUSIONS: The characterization of flies obtained in this study may be useful for defining locations of urban or semi-urban composting facilities. It also highlights the importance of sanitary precautions at such plants.

Animals↗
PubMed1999

Intron insertion as a phylogenetic character: the engrailed homeobox of Strepsiptera does not indicate affinity with Diptera.

The phylogenetic relationships of the order Strepsiptera are unclear. Affiliation to Coleoptera has been proposed, however this implies that dipteran halteres and strep-sipteran haltere-like organs evolved convergently. An alternative is a sister group relationship with Diptera. In this case, halteres could be homologous but a radical homeotic mutation may have switched their position to the Strepsipteran mesothorax. Ribosomal DNA sequence analysis has been used to support Dipteran affiliation, although this is controversial. Here we investigate the potential of an intron insertion site as a phylogenetic character. We find that the en homeobox gene of the strepsipteran Stichotrema dallatorreanum lacks a derived intron insertion shared by representatives of Diptera and Lepidoptera. We argue against a close affiliation between Strepsiptera and Diptera.

Amino Acid Sequence↗
PubMed1998

Visual system of the stalk-eyed fly, Cyrtodiopsis quinqueguttata (Diopsidae, Diptera): an anatomical investigation of unusual eyes.

Diopsid flies have eye stalks up to a centimeter in length, displacing the retina laterally from the rest of the head. This bizarre condition, called hypercephaly, is rare, but has evolved independently among several insect orders and is most common in flies (Diptera). Earlier studies of geometrical optics and behavior have led to various hypotheses about possible adaptive advantages of eye stalks, such as enhanced stereoscopic vision while other hypothesis suggest that eye stalks are an outcome of sexual selection. Here, we focus on how these curious distortions of head/eye morphology are accompanied by changes in the neural organization of the visual system of Cyrtodiopsis quinqueguttata. Histological examinations reveal that the optic lobes, lamina (La), medulla (Me), lobula (Lo), and lobula plate (LP) are contained entirely within the fly's eye bulbs, which are located at the distal ends of the eye stalks. We report that the organization of the peripheral visual system (La and Me) is similar to that of other Diptera (e.g., Musca and Drosophila), but deeper visual areas (Lo and LP) have been more strongly modified. For example, in both the lobula and lobula plate, fewer but larger giant collector neurons are found. The most pronounced difference is the reduction in the number of wide-field vertical cells of the lobula plate, where there are only four relatively large fibers, as opposed to 11 in Musca. The "fewer but larger" neural organization may enhance the conduction velocities of these cells, but may result in a loss of spatial resolution. At the base of the eye bulb, axon bundles collect and form a long optic nerve that extends the length of the eye stalk. We suggest that this organization of the diopsid visual system provides evidence for the costs of possessing long eye stalks.

Adaptation, Physiological↗
PubMed1996

Olfactory basis of host location by mosquitoes and other haematophagous Diptera.

The behavioural role of odours released by mosquito hosts is poorly understood, indeed for many species it is still uncertain whether olfactory cues play a significant part in host location. Generalist attractants, such as CO2, have found application in mosquito trapping systems, and yet more host-specific attractants, such as L-lactic acid, remain of questionable value. Recent work with other haematophagous Diptera, notably Glossina, has shown that by a co-ordinated multidisciplinary approach it is possible to develop odour-baited trapping systems with a high level of attractiveness and specificity. Many of the compounds shown to attract Glossina have been tested with mosquitoes, and one of these, 1-octen-3-ol, attracts female mosquitoes of a number of species, but only in the presence of CO2. The behavioural significance of other compounds identified as host attractants of haematophagous Diptera, such as phenols, indoles and carboxylic acids, are currently under investigation. Efforts to produce a host odour attractant for the highly anthropophilic species Anopheles gambiae have been hindered by the chemical nature of the compounds associated with its human host, although a number of short-chain fatty acids identified in sweat samples have been shown to be electrophysiologically active.

Animals↗
PubMed1990

Descending neurons supplying the neck and flight motor of Diptera: physiological and anatomical characteristics.

In Diptera, dorsal neuropils of the pro-, meso-, and metathoracic ganglia supply motor neurons to neck and flight muscles. Motor circuits are supplied by more than 50 pairs of descending neurons (DNs) whose dendritic trees in the brain are restricted to dorsal neuropils of the deutocerebrum where they are grouped together into discrete clusters. Each cluster is visited by wide-field motion-sensitive neurons and by morphologically small-field retinotopic elements. This organization suggests that flight descending neurons should respond to complex stimuli reflecting panoramic movement and small-field motion. Intracellular recordings, combined with dye filling, confirm this. Certain descending neurons responding to visual flow fields terminate bilaterally in superficial pterothoracic neuropils, at the level of indirect (power) flight muscle motor neurons. Other DNs terminate laterally, and provide segmental collaterals to areas containing neck and direct (steering) flight muscle motor neurons. Such DNs are activated by wide-field directional stimuli corresponding to pitch, roll, or yaw, and to small-field stimuli. Appropriate directional mechanosensory stimuli also activate dorsal descending neurons. The significance of dorsal descending neurons for the control of flight is discussed and compared with studies on course deviation neurons in other insects. It is suggested that, in Diptera, dorsal descending neurons may separately be involved in the control of velocity, stabilization, and steering manoeuvres.

Animals↗
PubMed1982

Molecular evolution of Drosophila and higher Diptera. I. Micro-complement fixation studies of a larval hemolymph protein.

LHP is a suitable protein for studying evolution in flies (Diptera). This blood protein, which occurs at high concentration late in larval development, was purified to homogeneity from 5 species of Drosophilidae and one species each of Tephritidae and Calliphoridae. Rabbit antisera to the purified LHPs allowed immunological comparisons to be made with the micro-complement fixation technique. Various indirect tests indicated that immunological distance is a reliable estimator of the degree of amino acid sequence difference between LHPs from different species. An evolutionary tree for the 7 LHPs was constructed from the immunological distances with the method of Fitch and Margoliash (1967) to provide the branching order and the method of Chakraborty (1977) to provide the branch lengths. A modified method of tree construction allowed LHPs from 10 additional species to be attached to this tree. The resulting LHP tree for 17 species agrees approximately in branching order with that based on Throckmorton's study of 60 anatomical traits. However, the ratio of anatomical change to LHP change along branches within the tree varies widely, confirming the independence of organismal and molecular evolution. The LHP tree thus provides a new perspective on evolution within and among the families of higher Diptera.

Animals↗
PubMed2000

Parallel alterations in the timing of ovarian ecdysone receptor and ultraspiracle expression characterize the independent evolution of larval reproduction in two species of gall midges (Diptera: Cecidomyiidae).

Although most insects reproduce in the adult stage, facultative larval or pupal reproduction (paedogenesis) has evolved at least six times independently in insects, twice in gall midges of the family Cecidomyiidae (Diptera). Paedogenesis in gall midges involves the precocious growth and differentiation of the ovary in an otherwise larval form. We have previously shown that the timing of expression of the Ecdysone Receptor (EcR) and Ultraspiracle (USP), the two proteins that constitute the functional receptor for the steroid hormone 20-hydroxyecdysone, regulates the timing and progression of ovarian differentiation in Drosophila melanogaster (Diptera: Drosophilidae). Here we test the hypothesis that precocious activation of EcR and USP in the ovaries of paedogenetic gall midges allows for precocious ovarian differentiation. Using monoclonal antibodies directed against insect EcR and USP proteins, we first show that when these gall midges are reared under conditions that promote typical, metamorphic development, up- regulation of EcR and USP occurs in the final larval stage. By contrast, in the paedogenetic life cycle, EcR and USP are up-regulated early in the first larval stage. A similar pattern is seen for two independently-evolved paedogenetic gall midges, Heteropeza pygmaea and Mycophila speyeri. We discuss our results in the context of developmental constraints on the evolution of paedogenesis in dipteran insects.

Animals↗
PubMedDate not supplied

Origin and evolution of the Amyrel gene in the alpha-amylase multigene family of Diptera.

Alpha-amylase genes often form multigene families in living organisms. In Diptera, a remote paralog, Amyrel, had been discovered in Drosophila, where this gene is currently used as a population and phylogenetic marker. The putative encoded protein has about 40% divergence with the classical amylases. We have searched the presence of the paralog in other families of Diptera to track its origin and understand its evolution. Amyrel was detected in a number of families of Muscomorpha (Brachycera-Cyclorrapha), suggesting an origin much older than previously thought. It has not been found elsewhere to date, and it is absent from the Anopheles gambiae genome. The intron-exon structures of the genes found so far suggest that the ancestral gene (before the duplication which gave rise to Amyrel) had two introns, and that subsequent, repeated and independent loss of one or both introns occurred in some Muscomorpha families. It seems that the Amyrel protein has experienced specific amino acid substitutions in regions generally well conserved in amylases, raising the possibility of peculiar, functional adaptations of this protein.

Amino Acid Motifs↗
PubMed2002

Gene duplication at the achaete-scute complex and morphological complexity of the peripheral nervous system in Diptera.

The number of achaete-scute genes increased during insect evolution, particularly in the Diptera lineage. Sequence comparison indicates that the four achaete-scute genes of Drosophila result from three independent duplication events. After duplication, the new genes acquired individual expression patterns but, in Drosophila, their products can compensate for one another, which raises the question: why retain all four genes? The complexity of the spatial expression of these genes on the notum increased in the lineage leading to the higher Diptera, allowing the development of stereotyped bristle patterns. This probably coincided in time with gene duplication events, raising the possibility that an increase in gene copy number might have provided the flexibility necessary for more complex transcriptional regulation.

Amino Acid Sequence↗
PubMed2001

Factors affecting decomposition and Diptera colonization.

Understanding the process of corpse decomposition is basic to establishing the postmortem interval (PMI) in any death investigation even using insect evidence. The sequence of postmortem changes in soft tissues usually gives an idea of how long an individual has been dead. However, modification of the decomposition process can considerably alter the estimate of the time of death. A body after death is sometimes subject to depredation by various types of animals among which insects can have a predominant role in the breakdown of the corpse thus, accelerating the decomposition rate. The interference of the insect community in the decomposition process has been investigated by several experimental studies using animal models and very few contributions directly on cadavers. Several of the most frequent factors affecting PMI estimates such as temperature, burial depth and access of the body to insects are fully reviewed. On account of their activity and world wide distribution, Diptera are the insects of greatest forensic interest. The knowledge of factors inhibiting or favouring colonization and Diptera development is a necessary pre-requisite for estimating the PMI using entomological data.

Animals↗
PubMed2000

Extraordinary feeding behaviour in Diptera Sciomyzidae, snail-killing flies.

In the laboratory, the larva of Sepedonella nana, Diptera Sciomyzidae, were only able to develop at the expense of small aquatic oligochets collected in adult habitats. Up till now, larval cycles have been elucidated for 38% of the Sciomyzidae; all these larvae proved to be strict consumers of aquatic or terrestrial molluscs (including slugs). This specific predation was considered as a major distinguishing characteristic of Sciomyzidae among Diptera. The unusual nutritional behaviour of S. nana reported in the present note is in contradiction with well-established prior knowledge. The species presented all the characteristics of the family, particularly the ventral arch sclerite present on the larva cephalopharyngeal skeleton. It was considered as a derived species; this behaviour, probably of secondary type, revealed new nutritional types for Afrotropical Sciomyzidae for which the biology of only five species was elucidated out of about 60 species described.

Animals↗