Morphology and ultrastructure of the spermatozoa of Lonchoptera lutea Panzer, 1809 (Diptera: Lonchopteridae).

Lonchoptera lutea males produce giant spermatozoa that are more than 2000 µm long and 1.4 µm wide. Unlike the typical brachyceran spermatozoon, they have a highly asymmetrical cross-section with only a single, albeit very large, mitochondrial derivative and a pair of massive accessory bodies, one of which extends throughout the entire length of the sperm tail. The accessory bodies consist of an electron-dense matrix in which numerous peculiar electron-lucid substructures are embedded. In the mated female, the giant spermatozoa are found inside two tubular spermathecae which are also extremely long, measuring 4000 µm or more.

A world review of reported myiases caused by flower flies (Diptera: Syrphidae), including the first case of human myiasis from Palpada scutellaris (Fabricius, 1805).

Rat-tailed larvae of the syrphid species Palpada scutellaris (Fabricius, 1805) are documented causing an enteric human myiasis in Costa Rica. This is the first time that the genus Palpada is recorded as a human myiasis agent. We report a 68-year-old woman with intestinal pain and bloody diarrhea with several live Palpada larvae present in the stool. Using molecular techniques (DNA barcodes) and both electronic and optical microscopy to study the external morphology, the preimaginal stages of the fly were unambiguously identified. An identification key to all syrphid genera actually known as agents of human and animal myiases is provided for larvae, puparia, and adults. Moreover, a critical world review of more than 100 references of Syrphidae as myiasis agents is also given, with emphasis on the species with rat-tailed larvae.

Visual motion sensitivity in descending neurons in the hoverfly.

Many animals use motion vision information to control dynamic behaviors. For example, flying insects must decide whether to pursue a prey or not, to avoid a predator, to maintain their current flight trajectory, or to land. The neural mechanisms underlying the computation of visual motion have been particularly well investigated in the fly optic lobes. However, the descending neurons, which connect the optic lobes with the motor command centers of the ventral nerve cord, remain less studied. To address this deficiency, we describe motion vision sensitive descending neurons in the hoverfly Eristalis tenax. We describe how the neurons can be identified based on their receptive field properties, and how they respond to moving targets, looming stimuli and to widefield optic flow. We discuss their similarities with previously published visual neurons, in the optic lobes and ventral nerve cord, and suggest that they can be classified as target-selective, looming sensitive and optic flow sensitive, based on these similarities. Our results highlight the importance of using several visual stimuli as the neurons can rarely be identified based on only one response characteristic. In addition, they provide an understanding of the neurophysiology of visual neurons that are likely to affect behavior.

The role of phosphorylation in the elasticity of the tethers that connect telomeres of separating anaphase chromosomes.

Elastic tethers, connecting telomeres of all separating anaphase chromosome pairs, lose elasticity when they lengthen during anaphase. Treatment with phosphatase inhibitor CalyculinA causes anaphase chromosomes to move backwards after they reach the poles, suggesting that dephosphorylation causes loss of tether elasticity. We added 50nM CalyculinA to living anaphase crane-fly spermatocytes with different length tethers. When tethers were short, almost all partner chromosomes moved backwards after nearing the poles. When tethers were longer, fewer chromosomes moved backwards. With yet longer tethers none moved backward. This is consistent with tether elasticity being lost by dephosphorylation. 50nM CalyculinA blocks both PP1 and PP2A. To distinguish between PP1 and PP2A we treated cells with short tethers with 50nM okadaic acid which blocks solely PP2A, or with 1µM okadaic acid which blocks both PP1 and PP2A. Only 1µM okadaic acid caused chromosomes to move backward. Thus, tether elasticity is lost because of dephosphorylation by PP1.

Human ophthalmomyiasis caused by Oestrus ovis-first report from Croatia and review on cases from Mediterranean countries.

Oestrus ovis is the most common cause of human ophthalmomyiasis. So far, majority of ophthalmomyiasis cases have been reported from Mediterranean countries, but not from Croatia. In current study, we present first two cases of human ophthalmomyiasis in Croatia, caused by O. ovis larvae. Reviewing a PubMed database, additional 259 cases of human ophthalmomyiasis in countries of Mediterranean basin have been reported. A total of 260 (99.62%) cases had external, while 1 (0.38%) had internal form of ocular myiasis. In all cases, O. ovis larvae were identified as the causative agent. O. ovis infestation is usually reported in shepherds and farmers although there is a high prevalence of infection in urban areas as well. Various climatic factors influence O. ovis larvipositional activity. Air temperature is the most important factor affecting O. ovis larviposition, while humidity, wind speed, and time of the day play only a moderate role. Most common symptoms of ophthalmomyiasis are irritation and redness, and in more than half of cases infestation is multiple. Ophthalmomyiasis interna is eye-compromising condition. Since there is reduced awareness among patients and medical professionals, the real number of ophthalmomyiasis cases is probably significantly higher than published. Global warming predisposes future increase of O. ovis prevalence in humans, which emphasizes the need for mandatory reporting and surveillance of disease.

Human Chrysomya bezziana myiasis: A systematic review.

BACKGROUND: Myiasis due to Old World screw-worm fly, Chrysomya bezziana, is an important obligate zoonotic disease in the OIE-list of diseases and is found throughout much of Africa, the Indian subcontinent, southeast and east Asia. C. bezziana myiasis causes not only morbidity and death to animals and humans, but also economic losses in the livestock industries. Because of the aggressive and destructive nature of this disease in hosts, we initiated this study to provide a comprehensive understanding of human myiasis caused by C. bezziana. METHODS: We searched the databases in English (PubMed, Embase and African Index Medicus) and Chinese (CNKI, Wanfang, and Duxiu), and international government online reports to 6th February, 2019, to identify studies concerning C. bezziana. Another ten human cases in China and Papua New Guinea that our team had recorded were also included. RESULTS: We retrieved 1,048 reports from which 202 studies were ultimately eligible for inclusion in the present descriptive analyses. Since the first human case due to C. bezziana was reported in 1909, we have summarized 291 cases and found that these cases often occurred in patients with poor hygiene, low socio-economic conditions, old age, and underlying diseases including infections, age-related diseases, and noninfectious chronic diseases. But C. bezziana myiasis appears largely neglected as a serious medical or veterinary condition, with human and animal cases only reported in 16 and 24 countries respectively, despite this fly species being recorded in 44 countries worldwide. CONCLUSION: Our findings indicate that cryptic myiasis cases due to the obligate parasite, C. bezziana, are under-recognized. Through this study on C. bezziana etiology, clinical features, diagnosis, treatment, epidemiology, prevention and control, we call for more vigilance and awareness of the disease from governments, health authorities, clinicians, veterinary workers, nursing homes, and also the general public.

Ejaculate sperm number compensation in stalk-eyed flies carrying a selfish meiotic drive element.

Meiotic drive genes cause the degeneration of non-carrier sperm to bias transmission in their favour. Males carrying meiotic drive are expected to suffer reduced fertility due to the loss of sperm and associated harmful side-effects of the mechanisms causing segregation distortion. However, sexual selection should promote adaptive compensation to overcome these deleterious effects. We investigate this using SR, an X-linked meiotic drive system in the stalk-eyed fly, Teleopsis dalmanni. Despite sperm destruction caused by drive, we find no evidence that SR males transfer fewer sperm to the female's spermathecae (long-term storage organs). Likewise, migration from the spermathecae to the ventral receptacle for fertilisation is similar for SR and wildtype male sperm, both over short and long time-frames. In addition, sperm number in storage is similar even after males have mated multiple times. Our study challenges conventional assumptions about the deleterious effects of drive on male fertility. This suggests that SR male ejaculate investment per ejaculate has been adjusted to match sperm delivery by wildtype males. We interpret these results in the light of recent theoretical models that predict how ejaculate strategies evolve when males vary in the resources allocated to reproduction or in sperm fertility. Adaptive compensation is likely in species where meiotic drive has persisted over many generations and predicts a higher stable frequency of drive maintained in wild populations. Future research must determine exactly how drive males compensate for failed spermatogenesis, and how such compensation may trade-off with investment in other fitness traits.

Comparative analysis reveals the complex role of histoblast nest size in the evolution of novel insect abdominal appendages in Sepsidae (Diptera).

BACKGROUND: The males of some sepsid species (Sepsidae: Diptera) have abdominal appendages that are remarkable in several ways. They are sexually dimorphic, have a complex evolutionary history of gain and loss, and can be jointed and thus highly mobile. The sternite brushes are used extensively in complex courtship behaviors that differ considerably between species and during mating. The abdominal appendages have a novel developmental pathway developing from histoblast nests rather than imaginal discs. RESULTS: We focus on the evolution of cell number, nest area, and segment length in both sexes to understand how this tissue relates to the formation of novel abdominal appendages. We map histoblast nest size of wandering-phase larvae of 17 species across 10 genera to a phylogenetic tree of Sepsidae and demonstrate that abdominal appendages require significant increases of histoblast nest size and cell number in most species while one species produces small appendages even without such modifications. In species with particularly large appendages, not only the nests on the fourth, but nests in neighboring segments are enlarged (Themira biloba, Themira putris). The loss of abdominal appendages corresponds to the loss of an enlarged fourth histoblast nest, although one species showed an exception to this pattern. One species that constitutes an independent origin of abdominal appendages (Perochaeta dikowi) uses an unusual developmental mechanism in that the histoblast nest sizes are not sexually dimorphic. CONCLUSIONS: The surprisingly high diversity in histoblast size and degree of sexual dimorphism suggests that the developmental mechanism used for abdominal appendage formation in sepsids is highly adaptable. The presence of appendages usually correlate with increased histoblast cell number and in most cases appendage loss results in a return to ancestral histoblast morphology. However, we also identify several exceptions that indicate the abdominal appendages have a malleable developmental origin that is responsive to selection.

Elastic 'tethers' connect separating anaphase chromosomes in a broad range of animal cells.

We describe the general occurrence in animal cells of elastic components ("tethers") that connect individual chromosomes moving to opposite poles during anaphase. Tethers, originally described in crane-fly spermatocytes, exert force on chromosome arms opposite to the direction the anaphase chromosomes move. We show that they exist in a broad range of animal cells. Thus tethers are previously unrecognised components of general mitotic mechanisms that exert force on chromosomes and they need to be accounted for in general models of mitosis in terms of forces on chromosomes and in terms of what their roles might be.

Gasterophilus intestinalis (Diptera: Oestridae) in the diaphragmatic muscle: An unusual finding.

Larval forms of the bot-fly Gasterophilus are obligate parasites commonly found in the gastrointestinal tract of equids, causing intestinal myiasis. Five species are reported so far in Italy, mostly observed during necroscopy, located in different portion of gastrointestinal tract of equids: G. intestinalis, G. nasalis, G. inermis, G. pecorum and G. haemorrhoidalis. An unusual finding of larval Gasterophilus intestinalis deeply inserted into the diaphragmatic muscle is here reported. Due to the uncommon localization, to the absence of clinical signs related to myiasis and subsequent uncertainty of species identity, identification was performed using an integrative taxonomical approach combining morphology with molecular tools for confirmatory reasons. This finding adds information on migration patterns of erratic larval forms in G. intestinalis, a feature of interest as gasterophiliasis is among the less studied intestinal myiasis of horses.

Taxonomy and First Records of Two Megaselia Rondani Species (Diptera: Phoridae) Preying upon Eggs of Phyllomedusa iheringii Boulenger (Anura: Phyllomedusidae).

Non-aquatic reproductive modes have evolved among frogs possibly favored by some advantages such as the avoidance of aquatic predators. These reproductive modes, however, make the egg clutches susceptible to terrestrial predators, among which Diptera larvae are some of the most harmful. The present work reports the predation by phorid flies of 22 egg clutches of Phyllomedusa iheringii Boulenger in the South of Brazil. Phorid specimens were identified as Megaselia bruchiana (Borgmeier & Schmitz) and Megaselia necrophaga (Enderlein), species that were reported previously to be associated with ants and dead beetles, respectively. Frog-feeding in these species is hypothesized to be use of an alternative seasonal food source. We amend the diagnoses of both Megaselia species and provide new illustrations to facilitate their identification. We also describe the male of M. bruchiana for the first time and associate males with females of both species.

Fat body and hemocyte contribution to the antimicrobial peptide synthesis in Calliphora vicina R.-D. (Diptera: Calliphoridae) larvae.

Antimicrobial peptides accumulated in the hemolymph in response to infection are a key element of insect innate immunity. The involvement of the fat body and hemocytes in the antimicrobial peptide synthesis is widely acknowledged, although release of the peptides present in the hemolymph from the immune cells was not directly verified so far. Here, we studied the presence of antimicrobial peptides in the culture medium of fat body cells and hemocytes isolated from the blue blowfly Calliphora vicina using complex of liquid chromatography, mass spectrometry, and antimicrobial activity assays. Both fat body and hemocytes are shown to synthesize and release to culture medium defensin, cecropin, diptericins, and proline-rich peptides. The spectra of peptide antibiotics released by the fat body and hemocytes partially overlap. Thus, the results suggest that insect fat body and blood cells are capable of releasing mature antimicrobial peptides to the hemolymph. It is notable that the data obtained demonstrate dramatic difference in the functioning of insect antimicrobial peptides and their mammalian counterparts localized into blood cells' phagosomes where they exert their antibacterial activity.

Sensory Trichites Associated With the Food Canal of Chrysops callidus (Diptera: Tabanidae).

Twelve pairs of putative sensory trichites (= sensilla) in the food canal of Chrysops callidus Osten Sacken are described. Eight paired trichites are located in the distal half of the food canal of all flies in the sample population (n = 26 females), but paired trichites 9 through 12 were found in variable numbers in the proximal half of the canal. Trichites were more closely spaced in the distal half of the food canal, and more widely spaced in the proximal half of the canal, indicating that monitoring blood flow is more critical in the distal region of the canal. Moreover, trichites were not precisely paired, with mean position for each right wall trichite 1 through 8 being slightly anterior to its counterpart in the left wall. A short, funnel-shaped vestibule was evident at the labrum terminus, opening distally to the outside and proximally into the food canal (the vestibule/food canal junction). There were two pairs of sensilla (one pair of basicone design, the other setiform) observed at the base of the vestibule just anterior to the junction of the vestibule with the food canal. These vestibular sensilla were constant in type, number and position, in every member of the sample population.

Giant spermatozoa of Diasemopsis (Diopsidae, Diptera) - Structural, ultrastructural and functional aspects.

The spermatozoa of Diasemopsis comoroensis and Diasemopsis meigenii differ from the conventional brachyceran type in several respects. Not only are they very long but they are also extraordinarily wide, especially at the very end of the tail. The latter is effected by two cellular components: oversized mitochondrial derivatives and a prominent central band, which is a peculiar structure not known from any other spermatozoa. Based on its position with respect to the other organelles and its origin during early spermiogenesis, the central band is interpreted as a derivative of the centriolar adjunct material. Like the axoneme, the mitochondrial derivatives and the central band extend through the entire length of the spermatozoon tail. The spermatozoon tail is helical and can be coiled up into a tight cone-shaped spiral with a peculiar corkscrew shaped end portion. The potential adaptive significance of these features and their coevolution with the morphology of the female's multi-chambered ventral receptacle are discussed, as are sperm competition and cryptic female choice.

Germ line transformation and in vivo labeling of nuclei in Diptera: report on Megaselia abdita (Phoridae) and Chironomus riparius (Chironomidae).

To understand how and when developmental traits of the fruit fly Drosophila melanogaster originated during the course of insect evolution, similar traits are functionally studied in variably related satellite species. The experimental toolkit available for relevant fly models typically comprises gene expression and loss as well as gain-of-function analyses. Here, we extend the set of available molecular tools to piggyBac-based germ line transformation in two satellite fly models, Megaselia abdita and Chironomus riparius. As proof-of-concept application, we used a Gateway variant of the piggyBac transposon vector pBac{3xP3-eGFPafm} to generate a transgenic line that expresses His2Av-mCherry as fluorescent nuclear reporter ubiquitously in the gastrulating embryo of M. abdita. Our results open two phylogenetically important nodes of the insect order Diptera for advanced developmental evolutionary genetics.

Encoding of yaw in the presence of distractor motion: studies in a fly motion sensitive neuron.

Motion estimation is crucial for aerial animals such as the fly, which perform fast and complex maneuvers while flying through a 3-D environment. Motion-sensitive neurons in the lobula plate, a part of the visual brain, of the fly have been studied extensively for their specialized role in motion encoding. However, the visual stimuli used in such studies are typically highly simplified, often move in restricted ways, and do not represent the complexities of optic flow generated during actual flight. Here, we use combined rotations about different axes to study how H1, a wide-field motion-sensitive neuron, encodes preferred yaw motion in the presence of stimuli not aligned with its preferred direction. Our approach is an extension of "white noise" methods, providing a framework that is readily adaptable to quantitative studies into the coding of mixed dynamic stimuli in other systems. We find that the presence of a roll or pitch ("distractor") stimulus reduces information transmitted by H1 about yaw, with the amount of this reduction depending on the variance of the distractor. Spike generation is influenced by features of both yaw and the distractor, where the degree of influence is determined by their relative strengths. Certain distractor features may induce bidirectional responses, which are indicative of an imbalance between global excitation and inhibition resulting from complex optic flow. Further, the response is shaped by the dynamics of the combined stimulus. Our results provide intuition for plausible strategies involved in efficient coding of preferred motion from complex stimuli having multiple motion components.

First report of external ophthalmomyiasis caused by Lucilia sericata Meigen in a healthy patient without predisposing risk factors.

A 72-year-old man with no medical history initially presented to the emergency room with severe tearing, redness, foreign body sensation, and pain in the left eye. He reported no previous history of any periocular trauma, malignancy, surgery, or systemic illness. On presentation, the patient only showed left periorbital edema and erythema in the left eyelid with no evidence of any skin malignancy. On slit lamp examination, multiple small whitish motile organisms were observed on the left conjunctival fornices. The organisms were removed, preserved, and identified as the third-stage larvae of Lucilia sericata (green bottle fly). The patient was treated with topical antibiotic and steroid eye drops and the inflammation resolved 1 week after treatment initiation. This is the first report of external ophthalmomyiasis caused by facultative parasite, L. sericata maggots in a healthy patient without any predisposing factors.

Complementary motion tuning in frontal nerve motor neurons of the blowfly.

Flies actively turn their head during flight to stabilize their gaze and reduce motion blur. This optomotor response is triggered by wide-field motion indicating a deviation from a desired flight path. We focus on the neuronal circuit that underlies this behavior in the blowfly Calliphora, studying the integration of optic flow in neck motor neurons that innervate muscles controlling head rotations. Frontal nerve motor neurons (FNMNs) have been described anatomically and recorded from extracellularly before. Here, we assign for the first time to five anatomical classes of FNMNs their visual motion tuning. We measured their responses to optic flow, as produced by rotations around particular body axes, recording intracellularly from single axons. Simultaneous injection of Neurobiotin allowed for the anatomical characterization of the recorded cells and revealed coupling patterns with neighboring neurons. The five FNMN classes can be divided into two groups that complement each other, regarding their preferred axes of rotation. The tuning matches the pulling planes of their innervated neck muscles, serving to rotate the head around its longitudinal axis. Anatomical and physiological findings demonstrate a synaptic connection between one FNMN and a well-described descending neuron, elucidating one important step from visual motion integration to neck motor output.

Molecular events underlying maggot extract promoted rat in vivo and human in vitro skin wound healing.

Maggot extracts promote wound healing, but their bioactive part(s) and molecular effects on the regenerating tissues/cells remain largely unclear. These issues are addressed here by treating rat skin wounds, human keratinocyte line/HaCat and fibroblasts with maggot secretion/excretion, and the extracts of maggots without and with secretion/excretion. The wound closure rates, cell proliferation activities, and statuses of wound healing-related signaling pathways (STAT3, Notch1, Wnt2, NF-κB, and TGF-beta/Smad3) and their downstream gene expression (c-Myc, cyclin D1, and VEGF) are evaluated by multiple approaches. The results reveal that the maggot extracts, especially the one from the maggots without secretion/excretion, show the best wound healing-promoting effects in terms of quicker wound closure rates and more rapid growth of keratinocytes and fibroblasts. Of the five signaling pathways checked, the ones mediated by TGF-beta/Smad3, and STAT3 are activated in the untreated wounds and become further enhanced by the maggot extracts, accompanied with c-Myc, VEGF, and cyclin D1 up-regulation. Our results thus show (1) that both body extract and secretion/excretion of maggots contain favorable wound healing elements and (2) that the enhancement of TGF-beta/Smad3 and STAT3 signaling activities may be the main molecular effects of maggot extracts on the wound tissues.

A 454 sequencing approach to dipteran mitochondrial genome research.

The availability of complete mitochondrial genome (mtgenome) data for Diptera, one of the largest metazoan orders, in public databases is limited. The advent of high throughput sequencing technology provides the potential to generate mtgenomes for many species affordably and quickly. However, these technologies need to be validated for dipterans as the members of this clade play important economic and research roles. Illumina and 454 sequencing platforms are widely used in genomic research involving non-model organisms. The Illumina platform has already been utilized for generating mitochondrial genomes without using conventional long range PCR for insects whereas the power of 454 sequencing for generating mitochondrial genome drafts without PCR has not yet been validated for insects. Thus, this study examines the utility of 454 sequencing approach for dipteran mtgenomic research. We generated complete or nearly complete mitochondrial genomes for Cochliomyia hominivorax, Haematobia irritans, Phormia regina and Sarcophaga crassipalpis using a 454 sequencing approach. Comparisons between newly obtained and existing assemblies for C. hominivorax and H. irritans revealed no major discrepancies and verified the utility of 454 sequencing for dipteran mitochondrial genomes. We also report the complete mitochondrial sequences for two forensically important flies, P. regina and S. crassipalpis, which could be used to provide useful information to legal personnel. Comparative analyses revealed that dipterans follow similar codon usage and nucleotide biases that could be due to mutational and selection pressures. This study illustrates the utility of 454 sequencing to obtain complete mitochondrial genomes for dipterans without the aid of conventional molecular techniques such as PCR and cloning and validates this method of mtgenome sequencing in arthropods.