Internal reproductive organs of the female humpbacked fly,Megaselia scalaris Loew (Diptera : Phoridae)

The female reproductive system of the humpbacked fly Megaselia scalaris Loew (Diptera : Phoridae) was examined in whole mount preparations and serial sections. The system includes 2 ovaries, paired lateral oviducts, a common oviduct, and a genital chamber, opening externally through a gonopore, anteriad and ventrad to the anus. The ducts of the 2 accessory glands open independently into the dorsal region of the genital chamber. The terminal duct of a 2-armed spermatheca joins the right posterior and ventral wall of the genital chamber, immediately inside the gonopore. Passing dorally, the spermathecal duct lies immediately ventral to the duct of the right accessory gland. A short distance posteriad, it divides into two branches, each supplying an arm of the spermatheca. The genital chamber extends both anteriorly and posteriorly from its junction with the common oviduct, creating anterior and posterior compartments. In the right lateral wall of the genital chamber, a distinctive loop-shaped thickening (plate) resembles a darkened thread when it is observed through the integument. Features likely to have taxonomic utility include the posterior and ventral location of the terminal portion of the spermathecal duct; and the asymmetrically arranged, loop-shaped plate.     

Ultrastructure of the larval salivary glands of Megaselia scalaris Loew (Diptera,Phoridae)

Each of the paired salivary glands of third instar larvae of the humpbacked fly Megaselia scalaris is a bag-like structure with a short neck region from which a single duct emerges. The two ducts form a common duct that empties into the ventral region of the pharynx near the mouthparts. The wall of the glands and ducts consists of a simple squamous epithelium that rests upon a connective tissue layer. Cells in the neck are less flattened than those found elsewhere. The basal surfaces of the cells are infolded most deeply in the neck and the least in the duct. The apical surfaces of the cells possess microvilli except in the duct where the apices of the cells are covered by a complex extracellular layer. This layer displays circularly arranged folds that accommodate a thread-like supportive structure resembling taenidial threads of tracheae. Elaborate junctional complexes are associated with the lateral surfaces of the cells. Elements of these complexes include a zonula adherens, a series of pleated septate desmosomes, and conventional desmosomes. The cytoplasm of the glandular cells is filled with RER and other organelles normally seen in cells that export proteins and mucosubstances. Secretory material found in the lumens of the glands reacts only moderately with the PAS procedure but more strongly with alcian blue and methods that demonstrate proteins. The nuclei of the glandular cells contain single large nucleoli and polytene chromosomes whose banding is rather indistinct. Treatment with EDTA produces detrimental effects on all of the foregoing ultrastructural features of the glands and ducts.     

Estimation of population profiles of two strains of the fly Megaselia scalaris (Diptera: Phoridae) by bootstrap simulation

Based on experimental population profiles of strains of the fly Megaselia scalaris (Phoridae), the minimal number of sample profiles was determined that should be repeated by bootstrap simulation process in order to obtain a confident estimation of the mean population profile and present estimations of the standard error as a precise measure of the simulations made. The original data are from experimental populations founded with SR and R4 strains, with three replicates, which were kept for 33 weeks by serial transfer technique in a constant temperature room (25 +/- 1.0 degrees C). The variable used was population size and the model adopted for each profile was a stationary stochastic process. By these simulations, the three experimental population profiles were enlarged so as to determine minimum sample size. After sample size was determined, bootstrap simulations were made in order to calculate confidence intervals and to compare the mean population profiles of these two strains. The results show that with a minimum sample size of 50, stabilization of means begins.     

Observations on first and second-instar larvae of Megaselia scalaris (Loew) (Diptera: Phoridae).

The ultrastructure of the first and second-instar larvae of Megaselia scalaris (Loew) was studied using scanning electron microscopy (SEM). Significant changes in morphological features were observed in the anterior and posterior spiracles, but only minimal changes in the labium and mouthhooks were seen. The ultrastructure of M. scalaris larvae not only provides chronological transformation of their larval instars, but it can also be used to explain their feeding behavior and mode of respiration. In addition, morphological structures useful for specific identification of first or second-instar larvae collected from human corpses may be used in forensic investigations.     

Ultrastructure of the spermatozoon of Megaselia scalaris Loew (Diptera:Brachycera:Cyclorrhapha:Phoridea:Phoridae)

When viewed by scanning electron microscopy (SEM), the spermatozoon of the phorid dipteran Megaselia scalaris appears threadlike, lacking distinct head and tail areas. These areas can be observed, however, in appropriately stained material. Measurements of Feulgen-stained material reveal average lengths of the head, tail, and total cell of 18.7, 128.7, and 147.4 μm, respectively. When tested for sulfhydryl and disulfide groups, the head displays only disulfide groups. Transmission electron microscopy (TEM) reveals 12 different regions: three (1–3) in the head, four (9–12) in the tail, and five (4–8) in a short zone of overlap between the head and tail. Most of the cell lies in regions 9 and 11 of the tail and 3 of the head, accounting for, respectively, 37.3%, 45.7%, and 11.2% of the total length. A tubelike acrosome indents the anterior end of the nucleus. The tail originates asymmetrically in relation to the long axis of the cell as a peglike structure associated with the dorsolateral region of the nucleus. No centriole is visible, and the nucleus has a notched appearance in longitudinal sections. Two mitochondrial derivatives and an axoneme displaying a 9+9+2 microtubule configuration and ATPase activity extend throughout most of the tail. In regions 9 and 10, an asymmetrically arranged accessory body is also present. Features having possible taxonomic utility include the asymmetrically arranged accessory body, the size and shape of the acrosome, and the notched appearance of the nucleus. The present report is apparently the first to describe the spermatozoon of a cyclorrhaphous dipteran which is not a member of the Schizophora.     

Structure,mitotic and meiotic behaviour,and stability of centromere-like elements devoid of chromosome arms in the fly Megaselia scalaris (Phoridae)

Minute elements detected in Megaselia scalaris (Phoridae, Diptera) lack chromosome arms but carry centromeres and possess kinetochore microtubules in mitosis as well as in meiosis. These centromere-like elements (CLEs) were present in two geographically independent strains of the fly. This indicates that their origin is not a recent event in the karyotype evolution of M. scalaris and that they are rather stable constituents of the karyotype. Most often, two CLEs were found in gonial and somatic mitosis. Spermatocytes contained one CLE. Two individuals examined deviated from this rule in that a metaphase spermatogonium showed three and an anaphase spermatogonium eight CLEs. These animals are believed to have been aneuploid relative to the CLEs. An analysis of spermatogonial division revealed that the CLEs behave like the centromeres of the regular chromosomes but seem to separate precociously, since they were closer to the spindle poles in late anaphase cells. Whereas the size of the CLEs was not significantly different between mitotic cells and secondary spermatocytes, the CLEs in primary spermatocytes were larger in volume by a factor of about 4.5 than those in mitosis and meiosis II. The additional material is interpreted as a glue that holds two CLEs together. This, in turn, is a prerequisite for orderly segregation. The function of the CLEs is not known. They are considered as B chromosomes reduced to the minimum required for segregation, the centromere.by J.B. RattnerAddress from April 1st 1991 until March 31st 1992: MRC, Human Genetics Unit, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, Scotland     

Chronic exposure to elevated levels of manganese and nickel is not harmful to a cosmopolitan detritivore, Megaselia scalaris (Diptera: Phoridae)

Environmental contamination with metals such as manganese (Mn) and nickel (Ni) often results in elevated concentrations of these metals in plant tissues. At high concentrations, these metals are known to have detrimental effects on certain insect herbivores. Using laboratory bioassays and artificial diet, we investigated the development and survival of a cosmopolitan insect detritivore, Megaselia scalaris (Diptera: Phoridae), exposed to concentrations of Mn and Ni reaching 2600 mg Mn/kg and 5200 mg Ni/kg dry mass (dm) in artificial diet. Surprisingly, Ni and Mn at the concentrations tested did not harm this fly. Treatment groups from diets with 260–2600 mg Mn/kg dm and 1300–5200 mg Ni/kg dm had significantly shorter larval development times, overall times to adult emergence, and both pupariation and pupal eclosion times compared to a control group. Wing length of females, a correlate of adult fitness, was also greater in metal treatment groups. Other measures including rate of egg hatch, percentage of emerging flies that were female, and wing length of male flies, were not significantly different in metal treatment groups. We conclude that Megaselia scalaris is tolerant of exceptionally high levels of Mn and Ni.     

Reactions of seven basic fluorochromes with unfixed cells obtained from the salivary glands of the dipteran fly Megaselia scalaris Loew (Phoridae)

Seven basic fluorochromes with varying specificities were used to stain the large squamous epithelial cells isolated from the larval salivary glands of Megaselia scalaris (Phoridae). Although the EDTA-based method selected for isolating the cells produced permeabilization and a loss of viability of the cells, consistent results were obtained with the various fluorochromes. The "classical" pattern of green nuclear and red cytoplasmic fluorescence observed in cells stained with acridine orange could be changed to green cytoplasmic and red nuclear fluorescence by pretreatment with RNase. The predominantly cytoplasmic and nucleolar fluorescence obtained with pyronine Y could be changed to mainly nuclear fluorescence by RNase pretreatment. The other five fluorochromes tested were not affected appreciably by extraction with RNase. Quinacrine mustard, dicarbocyanine (DiOC3(3)), and rhodamine 123 produced primarily cytoplasmic and nucleolar fluorescence, while nile red revealed mainly cytoplasmic lipid droplets. Phosphine 3R initially stained lipid droplets but very rapidly redistributed throughout the cytoplasm and nucleus. Because of their large size, flatness, and content of histochemically demonstrable components, the cells of Megaselia are especially appropriate for use as "optical objects" or controls in various studies. New methods of isolating the cells, however, will be needed to prevent permeabilization and loss of viability of the cells.     

Reactions of seven basic fluorochromes with unfixed cells obtained from the salivary glands of the dipteran fly Megaselia scalaris Loew (Phoridae)

Summary Seven basic fluorochromes with varying specificities were used to stain the large squamous epithelial cells isolated from the larval salivary glands of Megaselia scalaris (Phoridae). Although the EDTA-based method selected for isolating the cells produced permeabilization and a loss of viability of the cells, consistent results were obtained with the various fluorochromes. The classical pattern of green nuclear and red cytoplasmic fluorescence observed in cells stained with acridine orange could be changed to green cytoplasmic and red nuclear fluorescence by pretreatment with RNase. The predominantly cytoplasmic and nucleolar fluorescence obtained with pyronine Y could be changed to mainly nuclear fluorescence by RNase pretreatment. The other five fluorochromes tested were not affected appreciably by extraction with RNase. Quinacrine mustard, dicarbocyanine (DiOC₆(3)), and rhodamine 123 produced primarily cytoplasmic and nucleolar fluorescence, while nile red revealed mainly cytoplasmic lipid droplets. Phosphine 3R initially stained lipid droplets but very rapidly redistributed throughout the cytoplasm and nucleus. Because of their large size, flatness, and content of histochemically demonstrable components, the cells of Megaselia are especially appropriate for use as optical objects or controls in various studies. New methods of isolating the cells, however, will be needed to prevent permeabilization and loss of viability of the cells.     

A laboratory-based study for first documented case of urinary myiasis caused by larvae of Megaselia scalaris (Diptera: Phoridae) in Saudi Arabia

Megaselia scalaris (Diptera: Phoridae) is one of the medically important insects. Maggots from a urine sample of a 5-year-old Saudi girl were examined microscopically for identification. These maggots were cultured to become adult flies. Larvae and adults were identified using standard keys. Protozoan flagellates were obtained from the gut of the larvae. This is the first report of M. scalaris as a causative agent of urinary human myiasis in Saudi Arabia.     

Species richness estimations of the megadiverse scuttle fly genus Megaselia (Diptera: Phoridae) in a wildfire‐affected hemiboreal forest

Abstract The species richness of the scuttle fly (Diptera: Phoridae) genus Megaselia was estimated by various non‐parametric estimators from EstimateS, Species Prediction And Diversity Estimation (SPADE) and Ws2m, based on material from a Swedish hemiboreal forest area recently affected by major wildfires, Tyresta National Park and Nature Reserve (TNPNR), south of Stockholm. A total of 21 249 individuals were collected in Malaise traps, of which males constituted 16 976 and females 4 273. The analysed dataset represents 37 samples containing 18 549 specimens sorted into 330 species (184 described, 146 are either undescribed or of unsettled taxonomic status). It was not possible to estimate the total species richness using all samples due to heterogeneity caused by inclusion of different communities and temporal incoherencies between samples within and between years. Even with material obtained from a sampling program that was not designed for species richness estimates, it was possible to obtain reliable results when sample heterogeneity was minimized. By dividing the data into community‐specific datasets – for bog, forest and wildfire – it was possible to obtain asymptotic curves for the smaller of the two wildfire datasets. A total estimate of 357–439 (95% CI) was attained by using the smaller wildfire dataset and adding the 85 unique species from the samples not included in the estimation analysis. TNPNR has one of the richest known scuttle fly communities in Europe, consisting of almost 50% of the currently named Megaselia species; 48 of these species are reported as new records for Sweden in this study.     

Characterization of development, behavior and neuromuscular physiology in the phorid fly, Megaselia scalaris

The Phoridae is known as 'scuttle flies' because they walk in rapid bursts of movement with short pauses between. In this study, larval locomotive behavior and development was characterized in the phorid, Megaselia scalaris. Comparison was made with the well-characterized fruit fly model, Drosophila melanogaster. Developmentally, the rate of maturation was consistently slower for Megaselia than Drosophila. This disparity was exaggerated at lower temperatures, particularly during larval development. In addition to slower growth, movements in Megaselia were also slower, as evidenced by reduced rates of larval body wall contractions and mouth hook movements. Megaselia larvae also displayed a unique behavior of swallowing air when exposed to a small pool of liquid. This permitted floating upon immersion and, therefore, might prevent drowning in the natural environment. The anatomical and physiological properties of a neuromuscular junction in the phorid larvae were also examined. The innervation of the motor nerve terminals on the ventral abdominal muscle (m6) is innervated by Type Ib and Is axons, similar to Drosophila. As in Drosophila, the Is terminals produce larger excitatory postsynaptic potentials (EPSPs) than the Ib. The amplitudes of the EPSPs in M. scalaris were reduced compared to those of D. melanogaster, but unlike D. melanogaster the EPSPs showed marked facilitation when stimulated with a 20 Hz train. We conclude that there may be differences in synaptic structure of the nerve terminals that could account for the different electrophysiological behaviors.     

中国海南异蚤蝇属一新种记述(双翅目:蚤蝇科)

五指异蚤蝇Megaselia wuzhiensis,新种（图1～3） 雄性：额宽0．42mm,黑色,稀布细毛,纵沟细。触角上鬃4根,下对稍短;上对和下对间距分别是额宽的1／4和1／6。前额间鬃低于前额眶鬃及上触角上鬃,距眼缘和纵沟的距离比为1：3～1：2。后额间鬃低于后额眶鬃,四根鬃等距排列。触角第三节黑褐：芒亚端生,具微毛。下颚须黄色,具鬃5～7根。胸黑色。背中鬃2根;小盾片鬃2根,小毛2根：中侧片具毛,缺单鬃。翅长2．6mm。前缘脉指数0．53,各段比2．6：2．9：1,纤毛（最长）0．：24mm。腋区鬃3～6根。平衡棒黄褐色。足褐色,前足胫节0．68mm,跗节细长,各节长大于宽。中足胫节栅毛列伸达胫节端部1／5;后背纤毛7～9根。前背纤毛弱。后足股节1．2mm,腹缘细毛8～12根。胫节栅毛列完整,后背纤毛9～11根,强大：缺前背纤毛。腹部暗黑。背板Ⅱ和Ⅵ较长,其余背板近等长。背板稀被毛,两侧和后缘较多。尾器黑褐色,生殖背板两侧中部具鬃状毛;端部具小毛。肛管黄褐色。体长2．13～2．38mm。 正模：♂,海南五指山,1992—Ⅳ-16,刘广纯、王敏采：副模：5♂♂,同正模。 本种与缅甸产的M.atricornis Beyer相似,但后者前缘脉第二段短于第一段,额前侧鬃低于上触角上鬃。新种模式标本存于沈阳大学生物与环境工程学院标本室。     

A new species group in Megaselia,the lucifrons group,with description of a new species (Diptera,Phoridae)

With 1,400 described species, Megaselia is one of the most species-rich genera in the animal kingdom, and at the same time one of the least studied. An important obstacle to taxonomic progress is the lack of knowledge concerning the phylogenetic structure within the genus. Classification of Megaselia at the level of subgenus is incomplete although Schmitz addressed several groups of species in a series of monographs published from 1956 to 1981. Another problem is the lack of molecular phylogenetic analyses to support morphology-based conclusions. As a contribution towards addressing these problems, we here circumscribe a previously unrecognized monophyletic lineage of Megaselia consisting of species similar to Megaselia lucifrons. We base this taxonomic decision on morphological study of an extensive phorid material from Sweden, complemented by molecular analyses of select exemplars using two markers (COI and 28S). We name the clade the lucifrons species group, and show that it contains three distinct species. Our results also demonstrate that Megaselia subnitida Lundbeck, 1920, previously treated as a synonym of Megaselia lucifrons Schmitz, 1918, is a separate species, and we remove it from synonymy. The third species in the group was previously unknown; we describe it here as Megaselia albalucifrons sp. n.     

Alternative reproductive routines in a small fly, Puliciphora borinquenensis (Diptera: Phoridae)

Abstract. 1. Puliciphora borinquenensis (Wheeler), a very small phorid fly in which the female is apterous, breeds in small patches of decomposing organic matter such as dead insects. 2. Females leave the shelter of oviposition sites during the afternoon and ‘parade’ in exposed places making vigorous abdominal pumping movements which probably help to disperse a pheromone. 3. Males exhibit one of four reproductive routines. In the first they perform rapid sequences of stationary copulations with different parading females, achieving rates of 0.66 females min^-1 for periods of 30min (Al). In the second (A2) they wait on oviposition sites and grab non-parading females which have recently arrived. 4. In the third routine a male airlifts a parading female in copula to an oviposition site (Bl); in the final type of routine, females are airlifted and then deposited randomly when oviposition sites cannot be found (B2). 5. Males are able to learn the location of oviposition sites and this enables them to transport large numbers of females (up to thirty-three per male) to sites at a high rate (0.5 females min^-1). 6. Immediately a female is released after a B routine, the male follows her closely for up to 10s. This is thought to represent a phase of non-contact guarding, suggesting the occurrence of sperm competition. 7. Individual males persist with either A or B routines for long periods (c. 30 min), but they are able to switch between routines. 8. Young males (< 27 h after emergence) carry out A routines 18 times more commonly than B routines, whereas older males carry out A routines only 1.6 times more commonly than B routines. The choice between A and B routines in older flies does not depend on male or female density. 9. Males benefit from B routines because the eggs they fertilize are likely to reach oviposition sites, but they pay a considerable energy cost. A routines, on the other hand, are energetically cheaper, but mated females are less likely to reach oviposition sites unless they are subsequently transported by B males. An A male can then benefit provided his sperm are not completely displaced by the second male.     

The structure and surface properties of the eggshell of Megaselia imitatrix Borgmeier (Diptera, Phoridae) in relation to the respiration of the embryo

The role of the chorion in the mechanism of respiration is examined for the egg of Megaselia imitatrix. An air layer in the chorion is not essential for respiration, and oxygen can be absorbed through a hydrophilic pathway in the chorion by diffusion from the surrounding water. A model based on the diffusion of oxygen through the surface layer of the water down to the depth of the egg is proposed and presented in detail.     

Cytogenetic mapping of the W chromosome in the genus Leporinus (Teleostei, Anostomidae) using a highly repetitive DNA sequence

The distribution of the Leporinus elongatus LeSpeI repetitive sequence in other Leporinus species was studied in an attempt to elucidate the evolutionary history of sex chromosomes in this genus using chromosome fluorescence in situ hybridization. The presence of fluorescent signals only in species that have differentiated sex chromosomes suggests that this sequence is related to the differentiation of sex chromosomes in this genus. Thus, these data will contribute to a better understanding of chromosome evolution, especially for sex chromosomes, in the Leporinus genus.     

中国异蚤蝇属一新种及二新记录种记述(双翅目:蚤蝇科)

A new Megaselia species: Megaselia angustirostris Fang & Liu, sp. nov., is described and illustrated and two species of the genus, M. nigra (Meigen) and M. albicaudata (Wood), are reported for the first time from China. The type specimens are deposited in College of Biological and Environmental Engineering, Shenyang University.