Kimio Hirabayashi

Organic matter processing by chironomid larvae (Diptera: Chironomidae)

In laboratory experiments, we used fluorescent dye markers to investigate processing of organic matter by larvae of Psectrocladius limbatellus (Holm.) (Diptera: Chironomidae). 59% of the organic matter used was incorporated into tubes, 39% was present in faecal pellets (both after 24 h), and 2% was found in the larval gut at the end of experiments. Ingested matter passed through the gut rapidly, resulting in the gut being emptied more than 20 times each day. Further 24-h experiments using dye-marked faecal pellets showed that 6% of pellets produced were re-ingested and 12% were incorporated into tubes. There was no preference for conditioned faecal pellets as food over those that had recently been egested and tubes also provided a food reserve on which larvae feed. Chironomid larvae recycle organic matter resulting in its mineralization and their ‘engineering’ has a dramatic effect on the substratum.

Midge larvae (Diptera: Chironomidae) as engineers in slow sand filter beds

Abstract Midge larvae (Diptera: Chironomidae) are found abundantly (7.4×10 4 larvae m −2 ) in slow sand filter beds open to the atmosphere. Larvae eat the schmutzdecke accumulated at the sand surface and egest faecal pellets that are compacted and bound with mucopolysaccharides, faecal pellet size increasing with larval size. Pellets become diffuse after conditioning by microorganisms, and pellets, whether fresh or conditioned, are broken by abrasion. As up to 23% of the sand surface can be covered by fresh faecal pellets each day, midge larvae probably play an important role in the functioning of slow sand filters.

Studies of bronchial asthma induced by chironomid midges (Diptera) around a hypereutrophic lake in Japan

There have been few reports on hypersensitivity to chironomid midges in bronchial asthmatic patients around the area of hypereutrophic natural lakes, which have been notorious as an environmental hazard due to the massive occurrence of adult chironomids during several periods of the year. Our study investigated IgE antibodies to chironomid midges in bronchial asthmatic patients around the Lake Suwa area in comparison with those of the Matsumoto area (control area). A total of 123 adult patients with bronchial asthma were investigated by measurement of IgE antibodies with extracts of three chironomid midges (Chironomus yoshimatsui, C. plumosus, and Tokunagayusurika akamusi), mite, and silkworm. In addition, in the allergy testing, 12 common inhalant antigens were used. Of 123 adult patients with bronchial asthma, 65 (52.8%) produced positive allergy tests. Thirty‐three (50.8%) were positive to mite, 28 (43.1%) to silkworm, 11 (16.9%) to C. yoshimatsui, eight (12.3%) to C. plumosus, and three (4.6%) to T. akamusi. We compared our results with the previous reports. The number of positive tests to silkworm in the Lake Suwa area was higher than in other areas. However, C. plumosus and T. akamusi showed a lower number of positive reactions. We considered the lower positive number of C. plumosus and T. akamusi tests in the Lake Suwa area to be related to the advanced age of patients in this area. The chironomids are an important cause of asthma, together with mite and silkworm, in the Lake Suwa area, but affect old asthmatic patients less than asthmatic children.

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.

Population dynamics of Propsilocerus akamusi and Chironomus plumosus (Diptera: Chironomidae) in Lake Suwa in relation to changes in the lake's environment

Lake Suwa is a shallow eutrophic lake in central Japan. We have investigated the long-term population dynamics of chironomids in this lake. The objective of this study was threefold: (1) clarifying temporal variations in the emergence pattern of P. akamusi midges, (2) assessing dynamics in density, biomass and distribution pattern of Propsilocerus akamusi and Chironomus plumosus larvae in this lake, and (3) determining key factors that may affect these variations, as well as comparing the results of this study to those of previous reports. Emergence periods of P. akamusi midges from the lake have tended to become shorter in recent years. Furthermore, the mean daily catch of midges exhibits a clear decrease over time. In contrast, average densities of P. akamusi and C. plumosus larvae in the lake were 73.3±48.0 (SD) and 3.2±9.4 individuals per m2, respectively. Compared to 1986, this amounts to a decrease of about 1/70 and 1/130, respectively. Finally, the organic matter in the upper layer of the sediment has also been decreasing. This suggests that the basic conditions necessary for chironomid larvae habitats, especially quality and quantity of food, seem to be changing in Lake Suwa as water quality improves.

The efficiency of artificial wingbeat sounds for capturing midges in black light traps

This study was conducted to develop a new method to control adult Chironomus plumosus (L.) midges (Diptera: Chironomidae) using their acoustic responses to sound + light traps in the field. Trials were conducted from June 10 to June 27, 1996 near the hyper‐eutrophic Lake Suwa in central Japan. In cylindrical sound traps, optimal trapping of swarming males occurred at frequencies of 270–300 Hz at 22.5 °C. This effect was significantly enhanced using a sound trap equipped with a black light lamp. The mean number of midges captured by sound + light trap was about 4.5 times the number of midges caught by either light or sound trap alone. In conclusion, the application of audio‐frequency sounds combined with attraction to light for chironomid midge control seems to be quite feasible, assuming the availability of a suitable collecting device.

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. 31P-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.

Progress of eutrophication and change of chironomid fauna in Lake Yamanakako, Japan

Benthic macroinvertebrate distribution was studied on April 9, 1994, and March 2, 2003, in Lake Yamanakako. The average density of the benthic community for the entire lake was 3168 ind. m−2, comprising principally oligochaetes (41.0%) and chironomids (59.0%) in 1994. In 2003, the benthic community for the entire lake was 1847 ind. m−2, principally consisting of oligochaetes (69.9%) and chironomids (30.1%). In 1994, the larval density of Propsilocerus akamusi was 3.5 times that of Chironomus nipponensis and in 2003 the figure was 5.7 times. However, the larval biomass of P. akamusi was 2.1 times greater than that of C. nipponensis in 1994 and 2.8 times greater in 2003. The larval density of Tanypodinae decreased drastically, by about 12-fold, from 1994 to 2003. P. akamusi larvae were particularly abundant at the lake center in 1994, but they inhabited the entire lake bottom in 2003. P. akamusi density was closely related to water depth and ignition loss. C. nipponensis larvae also showed the widest distribution pattern in 2003, whereas their larvae had inhabited the northeastern parts and the lake center in 1994. Recently, the number of C. nipponensis larvae in Lake Yamanakako is tending to decrease, whereas that of P. akamusi larvae is increasing, suggesting ongoing eutrophication.

Temporal changes and vertical distribution of macrophytes in Lake Kawaguchi

Abstract The distribution of macrophytes in Lake Kawaguchi, Japan, was surveyed in August 1999 using a sampling anchor from a boat. The survey revealed that the present aquatic vegetation was composed of 17 submerged species, and no floating-leaved plants were present. The diversity of submerged plants and their vertical growth limits decreased progressively from the west to the east end of the lake. At the time of the survey, the dominant species was Elodea nuttallii (Planch.) St. John, which had once grown explosively in the mid-1980s in the lake, and except for Vallisneria asiatica Miki, all of the species commonly observed in the lake seem to have diminished their growth greatly. Among them, Potamogeton compressus L., which was the most dominant species in the lake before the invasion of Elodea nuttallii, had decreased most severely. It is suggested that the present state of aquatic vegetation in this lake was much influenced by the persistent growth of Elodea nuttallii as well as by environmental factors.

Field Study on Acoustic Response of Chironomid Midges (Diptera: Chironomidae) Around a Hyper-Eutrophic Lake in Japan

Abstract A new method was developed to control adult chironomid midges, Chironomus plumosus (L.) and Einfeldia dissidens (Walker), using their acoustic responses to sound traps in the field. Trials were conducted in 1999 from 2 to 7 June (during emergence period of E. dissidens ) and from 2 to 7 September (emergence period of C. plumosus ) near hyper-eutrophic Lake Suwa in central Japan. Swarms of E. dissidens were formed at 1–3 m above the terrain and were observed from 1900 to 1930 hours. More than 97% of E. dissidens trapped from the swarms were males. In cylindrical sound traps, optimal trapping of swarming males occurred at a frequency of 240 Hz at 21.9 ± 2.3°C. Swarms of C. plumosus were formed at 1 m to >5 m above ground, and were observed from 1830 to 1900 hours. More than 88% of C. plumosus caught from the swarm were males, and optimal trapping of swarming males occurred at frequencies of 300–360 Hz at 20.7 ± 0.5°C. We compared our results with those of other chironomid species and attempted to clarify the relationship between female wing length and ambient air temperature. There was no correlation between the most attractive frequency and female wing length. However, a positive correlation existed between the most attractive frequency and air temperature. It is concluded that the most attractive frequency differed among species (interspecific) according to air temperature. These mechanisms may play an important role in isolation during chironomid swarming.