Predator-prey interactions on the wing: aerobatics and body size among dance flies and midges

Male dance flies (Diptera: Empididae) are major predators of mating swarms of male nonbiting midges (Diptera: Chironomidae). Studies have indicated that chironomid midges are excellent fliers with extraordinarily high wing muscle power, acceleration and tortuosity for their size. We compared the relative flight performance and morphometrics of male empidsEmpis tesselatta Meigen and their prey, Chironomus plumosus L., in a series of laboratory and field studies. High-speed digital video camera footage revealed that there were no significant differences between predator and prey in terms of straight-line acceleration or maximum flight velocity, although the mean speed of empids was higher. In curved flight, measured as tortuosity, the smaller chironomids held a considerable advantage over their larger predators. Flight muscle ratio (e.g. flight muscle mass/body mass) of chironomids was also greater in chironomids than in empids. In field studies, small male chironomids suffered much lower levels of predation than large males. This result is consistent with the prediction of small midges being less likely to be captured because of superior aerobatics, although we are unable to exclude empirically that empids select large male midges. We discuss the possible mechanisms of prey capture by empids given the greater manoeuvrability of their prey, the coevolutionary dynamics of flight performance and the apparent selective advantage of small size in male chironomids. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

The structure of the ovarian ball and oogenesis in Moniliformis dubius (Acanthocephala)

Seven to nine days after infection of the definitive host (rat) by cystacanths, the genital primordium of the female acanthocephalan is transformed from a fragmented mass of cells into discrete ovarian balls. This is accomplished by envelopment of free germinal cells by somatic tissue which originates from the ligament sac primordium. Germinal cell nuclei then undergo repeated mitoses until about 21 days of development, with concurrent formation of oogonial syncytia which occupy the interior of the ovarian balls. Oocytes, derived from these oogonia, move to the periphery of the germinal syncytia for differentiation, growth, fertilization, shell formation, and release from the ovarian ball. After oogonial proliferation ceases, continued growth of the ovarian ball apparently results from increase in size of already present cells. Free-floating mature ovarian balls are found in the dorsal ligament sac; each consists of germ cells in various developmental stages, enveloped and pervaded by a multinucleate matrix syncytium of somatic origin, which functions as a follicle. Spermatozoa pass through the matrix cell for the internal fertilization of mature oocytes. Myelinated structures of an undetermined nature were found to correspond to previously reported polar bodies. After 100 days post-infection, the somatic matrix syncytium begins to manifest the degenerative effects of aging. The germinal tissue exhibits no subcellular signs of senescence by 154 days, but decreases in amount in older worms.     

Actin in oogenesis

Summary

The laser-scanning confocal microscope employed in conjunction with various specific agents and antibodies conjugated to fluorescent dyes reveals details of the actin scaffolding of developing oocytes and the nuclei of attendant cells. The employment of DNase I followed by anti-DNase I antibody has been particularly useful in revealing otherwise cryptic actin-containing structures. The cortical cytoskeleton of developing moth eggs was found to bind both poly (A)+RNA and RNA Pol II. Exposure to cytochalasin D disrupted the actin of the cortex, and at the same time caused redistribution of the proteins and RNA associated with the cytoskeleton. Cytochalasin also had dramatic effects on the structure of nuclei of nurse and follicle cells. Taken in context of the actin network in nuclei uncovered by DNase-anti-DNase treatment, these results suggest that actin plays a major structural and perhaps functional role in insect nuclei.     

Counting in oogenesis

The determination of a precise number of cells within a structure and of a precise number of cellular structures within an organ is critical for correct development in animals and plants. However, relatively little is known about the molecular mechanisms that ensure that these numbers are achieved. We discuss counting mechanisms that operate during ovarian development and oogenesis.     

吸血蠓及其传播的疾病

吸血蠓广泛分布世界各地,其危害不仅在于刺吸人畜等动物血液,而且是多种疾病的传播媒介。了解吸血蠓及其传播的疾病,对有效预防和控制吸血蠓及蠓媒病具有重要意义。     

The ovary structure and oogenesis in the basal crustaceans and hexapods. Possible phylogenetic significance

Recent large-scale phylogenetic analyses of exclusively molecular or combined molecular and morphological characters support a close relationship between Crustacea and Hexapoda. The growing consensus on this phylogenetic link is reflected in uniting both taxa under the name Pancrustacea or Tetraconata. Several recent molecular phylogenies have also indicated that the monophyletic hexapods should be nested within paraphyletic crustaceans. However, it is still contentious exactly which crustacean taxon is the sister group to Hexapoda. Among the favored candidates are Branchiopoda, Malacostraca, Remipedia and Xenocarida (Remipedia + Cephalocarida). In this context, we review morphological and ultrastructural features of the ovary architecture and oogenesis in these crustacean groups in search of traits potentially suitable for phylogenetic considerations. We have identified a suite of morphological characters which may prove useful in further comparative studies.     

A DNA barcode library for 5,200 German flies and midges (Insecta: Diptera) and its implications for metabarcoding‐based biomonitoring

This study summarizes results of a DNA barcoding campaign on German Diptera, involving analysis of 45,040 specimens. The resultant DNA barcode library includes records for 2,453 named species comprising a total of 5,200 barcode index numbers (BINs), including 2,700 COI haplotype clusters without species‐level assignment, so called “dark taxa.” Overall, 88 out of 117 families (75%) recorded from Germany were covered, representing more than 50% of the 9,544 known species of German Diptera. Until now, most of these families, especially the most diverse, have been taxonomically inaccessible. By contrast, within a few years this study provided an intermediate taxonomic system for half of the German Dipteran fauna, which will provide a useful foundation for subsequent detailed, integrative taxonomic studies. Using DNA extracts derived from bulk collections made by Malaise traps, we further demonstrate that species delineation using BINs and operational taxonomic units (OTUs) constitutes an effective method for biodiversity studies using DNA metabarcoding. As the reference libraries continue to grow, and gaps in the species catalogue are filled, BIN lists assembled by metabarcoding will provide greater taxonomic resolution. The present study has three main goals: (a) to provide a DNA barcode library for 5,200 BINs of Diptera; (b) to demonstrate, based on the example of bulk extractions from a Malaise trap experiment, that DNA barcode clusters, labelled with globally unique identifiers (such as OTUs and/or BINs), provide a pragmatic, accurate solution to the “taxonomic impediment”; and (c) to demonstrate that interim names based on BINs and OTUs obtained through metabarcoding provide an effective method for studies on species‐rich groups that are usually neglected in biodiversity research projects because of their unresolved taxonomy.     

Community structure of carrion flies along an island gradient

species richness, abundance relations, exploitation efficiencies, and population dynamics were examined within four carrion fly communities from a small isolated island in the Baltic to the large island of Åland. A total of 23 species and 11408 Specimens were collected.
Species richness (studied by rarefaction) of potential carrion flies was lowest on the small isolated island, but the smallest number of species emerged from the second largest island. Lucilia illustris Meig, was the most numerous species at every site, comprising 46–56% of the potential breeders and 71–91% of the emerging flies. Exploitation efficiency, measured by the numbers of individuals emerging per gram of carrion, was highest on the smallest island, but faunal similarity and ordination analyses suggest that competition was more intense on the larger islands.     

Factors determining the structure and diversity of parasitoid complexes in tephritid fruit flies

Summary The relative importance of phylogenetic affinity of hosts versus their ecological characteristics in determining the composition of their parasitoid complexes was examined using the parasitoid complexes of six species of frugivorous fruit flies from Central Europe. The hosts were four Rhagoletis and two other trypetine species, ranging in their relatedness from host races to members of different genera. They also differed in ecological characteristics, utilizing host plants of three different families, and developing either as pulp- or seedfeeders inside the host fruit. These features made it feasible to test the following pair of hypotheses. The ecological hypothesis predicts that ecological traits such as host-plant and fruit fly phenologies and host-fruit texture should be more important for the composition of parasitoid complexes than the taxonomic relatedness of the fly species. Assuming that ecological relationships do not parallel phylogenetic ones, the alternative phylogenetic hypothesis predicts the opposite. In fruit and soil samples, taken between 1983 and 1989, three guilds of parasitoids comprising 20 species were found: guild 1 — koinobiotic larval parasitoids (e.g. Opius spp., which attack the host larvae but develop inside the host puparia); guild 2 — idiobiotic larval parasitoids (e.g. Pteromalus spp., which consume the host larvae at once); and guild 3 — idiobiotic puparium parasitoids (e.g. Phygadeuon spp.). Although some results support the phylogenetic hypothesis, the majority of results support the ecological hypothesis.     

Karyosphere in oogenesis]

The purpose of this review is to draw attention to the peculiar phenomenon during gametogenesis: the formation of the karyosphere. This phenomenon is characterized by concentration of all chromosomes in the limited area of the nucleus and may be considered as alternative of the genome in the state of lumpbrush chromosomes. The formation of the karyosphere is a widely spread phenomenon during oogenesis of different animal classes. The karyosphere can be developed during different stages of oogenesis in different organisms; but as a rule the chromosomes of diploten stage of meiosis take part in its formation. As to functional identity of the karyosphere in different species, special investigations are to be done, but contemporary knowledge of the karyosphere formation reveals some common feature:1) in the karyosphere the chromosomes are in a relatively spiral state as demonstrated by the positive Feulgen reaction; 2) there is a low level of RNA synthesis or the absence of it in the karyosphere; 3) during the karyosphere formation the nucleus is enriched by the acid proteins and a lot of protein granules and structures appearing in a close contact with the karysphere. The more typical examples of the karyosphere formation can be observed in the insect oocytes belonging to the nutrimentary type of oogenesis. In the oocytes of some animals the peculiar protein substances are formed around the chromosome knot and appear as a fibrillar zone. Such karyosphere appears to be a kind of capsule inside the nucleus. The capsules are developed as a result of complex interaction between the main nuclear structures; chromosomes, nucleoli, and nuclear membrane as it is manifested by the analysis of some recent ultrastructural date obtained in some insect and amphibian oocytes. The function of the karyosphere capsule and the role of the nuclear structure (sinaptonemal complex, extrachromosomal DNA, and nuclear membrane) in formation of the capsule, are discussed as well as the ultrastructural and cytochemical similarity between the karyosphere capsule of oocytes and nuclear bodies of somatic cells.     

The fine structure of the pupal plastron of simuliid flies

The outer surface of the plastron of the pupal spiracular gills of the Simuliidae was previously thought to be the network formed by the apical branches of the vertical struts. It is now shown that this horizontal network supports a thin laminate outer epicuticle and also a fine meshwork, both of which have been previously overlooked. A simple method is described for quickly producing three-dimensional micrographs of great depth with the transmission electron microscope.     

U-cadherin in Xenopus oogenesis and oocyte maturation

U-cadherin is a member of the cadherin family in Xenopus that participates in interblastomere adhesion in the early embryo from the first cleavage onwards. Though a maternal pool of U-cadherin is available in the egg, it is not present on the egg membrane (Angres et al., 1991. Development 111, 829-844). To assess the origin of this unexpected distribution in the egg, the accumulation and localization of the cadherin during oogenesis and oocyte maturation were investigated. We report here that U-cadherin is present in Xenopus oocytes throughout oogenesis. It is localized at the oocyte-follicle cell contacts suggesting that it functions in the adhesion of the two cell types. When oocytes mature and the contacts to the follicle cells break, U-cadherin disappears from the oocyte surface. Evidence for a translocation of U-cadherin from the membrane to the inside of the oocyte was obtained when the fate of membrane-bound U-cadherin, which was labelled on the surface of oocytes prior to maturation, was followed through maturation. The total U-cadherin content of the oocyte increases during maturation. Metabolic labelling experiments indicate that at maturation the translation of U-cadherin is elevated well above the level that one would expect from the general increase in protein synthesis is presumably the main source of the maternal pool of U-cadherin in the egg.     

Systems-level questions in Drosophila oogenesis

This paper describes computational and experimental work on pattern formation in Drosophila egg development (oogenesis), an established experimental model for studying cell fate diversification in developing tissues. Epidermal growth factor receptor (EGFR) is a key regulator of pattern formation and morphogenesis in Drosophila oogenesis. EGFR signalling in oogenesis can be genetically manipulated and monitored at many levels, leading to large sets of heterogeneous data that enable the formulation of increasingly quantitative models of pattern formation in these systems.     

DNA repair in Drosophila oogenesis

In experiments with females of lines with an impaired DNA repair systems mei-9 (impaired excision repair) and mei-41 (impaired postreplicative repair), a method of successive irradiation by X-rays (1000 R) and hyperthermia (+37 degrees C) action was used for the purpose of defining a moment when DNA repair takes place in oogenesis. Repair in mature mei-41 oocytes judged of by synergism effect of the both factors acting was ascertained to take place right after X-raying (prior to DNA replication) and being absent at the fertilization period (at the time of or after DNA replication). DNA repair in mei-9 females was not registered in both cases. On the basis of these facts, it is suggested that coordination of various DNA repair systems is necessary for damaged chromosomes to be repaired. It is also concluded that the method used can be regarded as an effective technique in the study of mutation process.     

Age structure and abundance in populations of muscoid flies from a poultry facility in Southeast Brazil

Muscina stabulans, M. domestica, Chrysomya putoria, C. megacephala and Stomoxys calcitrans were the most abundant muscoid flies captured in a poultry facility in southeastern Brazil. We examined the gonadotrophic profiles of the females caught at different sites and different times and found that Mu. stabulans and M. domestica, the predominant species, presented similar gonadotrophic profiles only when captured on the manure under the cages, but very different and sometimes opposite gonadotrophic profiles when sampled from wooden posts, vegetation or electric cords. We also determined sex ratios and relative abundance for these two species and found significant differences between them. More than 50% of the females of both species of Chrysomya captured on manure carried eggs or exhibited signs of recent oviposition. The vast majority of S. calcitrans presented ovaries with eggs or signs of recent oviposition. A small proportion of them had ovaries in the recent emerged condition. Our data on ovarian stages, sex ratio and relative abundance allowed us to associate different gonadotrophic profiles with each site and characterize each site as a resting, ovipositing or mating site.     

Phylogenetic analysis of correlation structure in stalk-eyed flies (Diasemopsis,Diopsidae)

Morphological divergence among species may be constrained by the pattern of genetic variances and covariances among traits within species. Assessing the existence of such a relationship in nature requires information on the stability of intraspecific correlation and covariance structure and the correspondence of this structure to the pattern of evolutionary divergence within a lineage. Here, we investigate these issues for nine morphological traits and 15 species of stalk-eyed flies in the genus Diasemopsis. Within-species matrices for these traits were generated from phenotypic data for all the Diasemopsis species and from genetic data for a single Diasemopsis species, D. dubia. The among-species pattern of divergence was assessed by calculating the evolutionary correlations for all pairwise combinations of the morphological traits along the phylogeny of these species. Comparisons of intraspecific matrices reveal significant similarity among all species in the phenotypic correlations matrices but not the covariance matrices. In addition, the differences in correlation structure that do exist among species are not related to their phylogenetic placement or change in the means of the traits. Comparisons of the phenotypic and phylogenetic matrices suggest a strong relationship between the pattern of evolutionary change among species and both the intraspecific correlation structure and the stability of this structure among species. The phenotypic and the phylogenetic matrices are significantly similar, and pairs of traits whose intraspecific correlations are more stable across taxa exhibit stronger coevolution on the phylogeny. These results suggest either the existence of strong constraints on the pattern of evolutionary change or a consistent pattern of correlated selection shaping both the phenotypic and phylogenetic matrices. The genetic correlation structure for D. dubia, however, does not correspond with patterns found in the phenotypic and phylogenetic data. Possible reasons for this disagreement are discussed.