Tiger prowling: Distribution modelling for northward-expanding Aedes albopictus (Diptera: Culicidae) in Japan.

The Asian tiger mosquito, Aedes albopictus, is a significant public health concern owing to its expanding habitat and vector competence. Disease outbreaks attributed to this species have been reported in areas under its invasion, and its northward expansion in Japan has caused concern because of the potential for dengue virus infection in newly populated areas. Accurate prediction of Ae. albopictus distribution is crucial to prevent the spread of the disease. However, limited studies have focused on the prediction of Ae. albopictus distribution in Japan. Herein, we used the random forest model, a machine learning approach, to predict the current and potential future habitat ranges of Ae. albopictus in Japan. The model revealed that these mosquitoes prefer urban areas over forests in Japan on the current map. Under predictions for the future, the species will expand its range to the surrounding areas and eventually reach many areas of northeastern Kanto, Tohoku District, and Hokkaido, with a few variations in different scenarios. However, the affected human population is predicted to decrease owing to the declining birth rate. Anthropogenic and climatic factors contribute to range expansion, and urban size and population have profound impacts. This prediction map can guide responses to the introduction of this species in new areas, advance the spatial knowledge of diseases vectored by it, and mitigate the possible disease burden. To our knowledge, this is the first distribution-modelling prediction for Ae. albopictus with a focus on Japan.

Elevational Distribution of the Asian Tiger Mosquito, Aedes albopictus, in the Inland Mountain Area of Nagano and Yamanashi Prefectures, Japan.

Nagano and Yamanashi prefectures of Japan comprise an inland mountain area that extends widely north and south, with elevation varying greatly by location. Mosquitoes transmitting infectious disease have a diversity of habitats in Nagano and Yamanashi, and many species can be expected there. However, there have been few reports on mosquito fauna; in particular, little information is available on mosquitoes such as Aedes albopictus. The mosquito fauna was investigated to clarify their elevational distribution ranging from 317 to 1,534 m, focusing especially on Ae. albopictus, in 24 areas in Nagano and Yamanashi prefectures from July to September in 2012-16. Adult mosquitoes were collected using the Centers for Disease Control and Prevention traps in each area, in addition to larval mosquito collections at several temple and shrine precincts in each area. At sites where elevations were >800 m (14 sites), no adult Ae. albopictus were captured. In addition, larval Ae. albopictus were not collected at elevations >728 m (15 sites). Aedes albopictus was captured at 20 other sites (annual mean air temperature ranged from 9.4 to 15.2°C, July-September mean air temperature ranged from 19.9 to 25.0°C).

Predicting the Start of the Aedes albopictus (Diptera: Culicidae) Female Adult Biting Season Using the Spring Temperature in Japan.

Aedes albopictus (Skuse) (Diptera: Culicidae) is distributed widely and is common in much of Japan. In Japan, female adults begin to bite in between April and June, except in the southern subtropics where the mosquito has no dormant period. It is difficult to estimate the first Ae. albopictus biting day because it varies annually depending on the location. Over several years, we surveyed the mosquitoes at different locations that covered a range of warmer to cooler areas of Japan. We found an association between the timing of first biting day by Ae. albopictus and spring temperature. In spring months, the strongest correlation was found with mean April temperatures, followed by March. Based on these data, it may, therefore, be possible to apply a simple formula to predict the timing of the first biting day at various geographical locations in Japan. Forecasting maps were created using a simple prediction formula. We found that the first biting day for Ae. albopictus changed depending on early spring temperatures for each year. There was an approximate 20-d difference in first biting day between years with warmer and cooler springs. This prediction model will provide useful insight for planning and practice of Ae. albopictus control programs, targeting larvae and adults, in temperate regions globally.

Phototaxis of Propsilocerus akamusi (Diptera: Chironomidae) From a Shallow Eutrophic Lake in Response to Led Lamps.

A study on the attraction of adult Propsilocerus akamusi midges to different-colored light traps was carried out from October 21 to November 15, 2013. The 6 colored lights used in light-emitting diode (LED) lamps were white, green, red, blue, amber, and ultraviolet (UV). The UV lamp attracted the most P. akamusi, followed by green, white, blue, amber, and red. A white pulsed LED light attracted only half the number of midges as did a continuous-emission white LED light. The result indicated that manipulation of light color, considering that the red LED light and/or pulsed LED light are not as attractive as the other colors, may be appropriate for the development of an overall integrated strategy to control nuisance P. akamusi in the Lake Suwa area.

Characterization of silk gland ribosomes from a bivoltine caddisfly, Stenopsyche marmorata: translational suppression of a silk protein in cold conditions.

Larval Stenopsyche marmorata constructs food capture nets and fixed retreats underwater using self-produced proteinaceous silk fibers. In the Chikuma River (Nagano Prefecture, Japan) S. marmorata has a bivoltine life cycle; overwintering larvae grow slowly with reduced net spinning activity in winter. We recently reported constant transcript abundance of S. marmorata silk protein 1 (Smsp-1), a core S. marmorata silk fiber component, in all seasons, implying translational suppression in the silk gland during winter. Herein, we prepared and characterized silk gland ribosomes from seasonally collected S. marmorata larvae. Ribosomes from silk glands immediately frozen in liquid nitrogen (LN2) after dissection exhibited comparable translation elongation activity in spring, summer, and autumn. Conversely, silk glands obtained in winter did not contain active ribosomes and Smsp-1. Ribosomes from silk glands immersed in ice-cold physiological saline solution for approximately 4 h were translationally inactive, despite summer collection and Smsp-1 expression. The ribosomal inactivation occurs because of defects in the formation of 80S ribosomes, presumably due to splitting of 60S subunits containing 28S rRNA with central hidden break, in response to cold stress. These results suggest a novel-type ribosome-regulated translation control mechanism.

Molecular cloning, gene expression analysis, and recombinant protein expression of novel silk proteins from larvae of a retreat-maker caddisfly, Stenopsyche marmorata.

Retreat-maker larvae of Stenopsyche marmorata, one of the major caddisfly species in Japan, produce silk threads and adhesives to build food capture nets and protective nests in water. Research on these underwater adhesive silk proteins potentially leads to the development of new functional biofiber materials. Recently, we identified four major S. marmorata silk proteins (Smsps), Smsp-1, Smsp-2, Smsp-3, and Smsp-4 from silk glands of S. marmorata larvae. In this study, we cloned full-length cDNAs of Smsp-2, Smsp-3, and Smsp-4 from the cDNA library of the S. marmorata silk glands to reveal the primary sequences of Smsps. Homology search results of the deduced amino acid sequences indicate that Smsp-2 and Smsp-4 are novel proteins. The Smsp-2 sequence [167 amino acids (aa)] has an array of GYD-rich repeat motifs and two (SX)4E motifs. The Smsp-4 sequence (132 aa) contains a number of GW-rich repeat motifs and three (SX)4E motifs. The Smsp-3 sequence (248 aa) exhibits high homology with fibroin light chain of other caddisflies. Gene expression analysis of Smsps by real-time PCR suggested that the gene expression of Smsp-1 and Smsp-3 was relatively stable throughout the year, whereas that of Smsp-2 and Smsp-4 varied seasonally. Furthermore, Smsps recombinant protein expression was successfully performed in Escherichia coli. The study provides new molecular insights into caddisfly aquatic silk and its potential for future applications.

Retrospective search for dengue vector mosquito Aedes albopictus in areas visited by a German traveler who contracted dengue in Japan.

A German traveler developed dengue fever in late August 2013, following a direct flight from Germany. Autochthonous dengue virus (DENV) infection has not been reported in Japan. To evaluate the risk of autochthonous DENV transmission in Japan, the authors performed a retrospective search of the five areas visited by the German patient to determine the population density of dengue vector mosquito, Aedes albopictus. The annual mean temperature of each area was higher than 12°C, which is considered suitable for the establishment of A. albopictus populations. Our retrospective search revealed the population density of A. albopictus to be high in the urban areas of Japan.

Long-range periodic sequence of the cement/silk protein of Stenopsyche marmorata: purification and biochemical characterisation.

The long-range periodic amino acid sequence of the bifunctional silk/cement protein from larvae of the caddisfly, Stenopsyche marmorata, is discussed in this study. The protein, named the S. marmorata silk protein (Smsp-1), was first purified to electrophoretic homogeneity. The results of Edman-based sequencing of Smsp-1 tryptic digests were consistent with the amino acid sequence deduced from a cDNA clone of the Smsp-1 gene. All undetected amino acids in the Edman-based sequencing were encoded as Ser, suggesting the presence of O-phospho-Ser. (31)P-NMR and an O-phospho-amino acid analysis successfully showed that the O-phospho-Ser residue occurred in a clustered manner, serving a cement function for Smsp-1. Two patterns of non-phosphorylated repeats, -SLGPYGDPRGDXLGPYGG- (X = V, G or D) and -GVGPYGDGLGPYGG-, were enriched in Smsp-1 compared with the O-phospho-Ser cluster, and have fibre-forming functions.

Physical properties and structure of aquatic silk fiber from Stenopsyche marmorata.

To study the properties and structure of aquatic silk, nest-spinning hydropsychid caddisfly (Stenopsyche marmorata) larva were collected from a Japanese river and the silk glands were removed from the larva by dissecting and dried on the glass plate at room temperature. The silk fibers were obtained by removing fibrous materials, which the aquatic insects spun at the bottom of glass container and the microstructure and physical properties of aquatic silk protein fibres and their solid silk protein gland were evaluated. Silk fiber produced by the caddisfly larvae is composed of two filament embedded in a layer of glue. The results of Fourier transform infrared spectroscopy and X-ray diffraction measurements suggested the existence of binary structure containing random coil conformation and additional minor beta-molecular structure. Differential scanning calorimetry results are characterized by two broad endothermic transitions, at 230 degrees C and 320 degrees C, which corresponds to the decomposition of silk glue and silk fiber from caddis fly, respectively. The storage modulus (E') remained almost unchanged and nearly constant at above 60 degrees C until about 214 degrees C, where it began to show a sharp drop. A prominent relaxation peak appeared in the imaginary part of the modulus (loss peak at 230 degrees C), in response to the strong motional transitions exhibited by the silk fiber at this temperature. There was significant difference of tensile strength of single solid silk protein gland in dry and wet state. The results obtained are quite promising as a basis for possible future biotechnological and adhesive applications of aquatic silk.

Long-term dynamics of freshwater red tide in shallow lake in central Japan.

OBJECTIVE: The aim of this study is to clarify the long-term dynamics of the red tide occurring in Lake Kawaguchi. METHODS: The measurement of environmental factors and water sampling were carried out monthly at a fixed station in Lake Kawaguchi's center basin from April 1993 to March 2004. On June 26, 1995, the horizontal distribution ofPeridinium bipes was investigated using a plastic pipe, obtaining 0∼1-m layers of water column samples at 68 locations across the entire lake. RESULTS: P. bipes showed an explosive growth and formed a freshwater red tide in the early summer of 1995, when the nutrient level was higher than those in the other years, particularly the phosphate concentration in the surface layer. The dissolved total phosphorus (DTP) concentration was sufficient forP. bipes growth in that year. In the study of its horizontal distribution,P. bipes was found at all the locations. The numbers of cells per milliliter ranged from 67 to 5360, averaging 1094±987 cells/ml, with particularly high densities along the northern shore. Since then,P. bipes has annually averaged about 25 cells/ml in Lake Kawaguchi. CONCLUSION: We observed that the red tide caused byP. bipes correlates with a high DTP concentration in Lake Kawaguchi.

Chironomid fauna (Diptera, Chironomidae) in a filtration plant in Japan.

Massive flights of chironomid midges have been observed frequently, and they have caused some problems in the daily life of residents around water treatment works. The development of physical and biological control strategies against chironomid midges is urgently needed because chemical control is not feasible in slow sand filter beds. In this study, in order to collect basic biological data for controlling the massive flights of chironomid midges, seasonal changes in the abundance and species composition of chironomid midges and larvae were investigated in slow sand filter beds. We identified 21 genera and 49 species belonging to 3 subfamilies. In spring, Cricotopus sylvestris and Rheopelopia maculipennis were the dominant species, whereas Polypedilum nubifer, Cricotopus trifasciatus, Chironomus kiiensis, and Procladius sagitalis were dominant in summer. Tanytarsus mendax and T. volgensis were the dominant species in fall. Polypedilum nubifer, C. sylvestris, and C. kiiensis were the major pest species in Japan. The overall factors influencing the abundance pattern of chironomids supposedly are temperature and the quality and quantity of food in slow sand filter beds.