Tempo-spatial variation in feeding activity and density of Aedes albopictus (Diptera: Culicidae) at peridomestic habitat in Nagasaki, Japan.

金沢大学理工研究域　自然システム学系1998年9月, 長崎大学熱帯医学研究所敷地内で家屋周辺の茂み及び裸地においてヒトスジシマカの24時間採集を行い, 周辺環境の異なる採集場所における吸血活動性と密度のちがいを調べた。ヒトスジシマカの密度は茂みで高く, 屋内や裸地で低かった。吸血活動は薄明薄暮に高まり, 夜も高かった。最も活動性が高い薄暮には, 統計的な有意差はみられないが, 昼間や夜間に比べて屋内や裸地で採集される雌個体の割合が高かった。以上の結果からヒトスジシマカの生態における夜間の吸血活動の重要性と薄明薄暮には茂み以外に裸地や屋内などでも吸血される機会が増加することが示唆された。 To clarify the tempo-spatial variation in feeding of Aedes albopictus, a field investigation was conducted in a field where the species heavily infested, in Nagasaki. Feeding activity was observed in the nighttime as well as at dawn and dusk. The density was high at sites with vegetation and low at sites without vegetation and indoors. At sites with vegetation, the proportion of females decreased at dawn and dusk, while it increased at sites without vegetation and indoors. Feeding activity in nighttime is possibly common in Ae. albopictus, and the place of feeding expands from sites with vegetation to sites without vegetation and indoors at dawn and dusk

Preliminary field experiments on exophagy of Aedes albopictus (Diptera: Culicidae) in peridomestic habitat.

金沢大学理工研究域　自然システム学系Preliminary field experiments were conducted to examine the exophagy of Aedes albopictus in peridomestic habitat by using three different types of experimental buildings in Nagasaki, Japan and Chiangmai, Thailand. The density of females collected by suction traps enhanced by CO2 was high inside net-walled buildings and at outdoor sites with vegetation. On the other hand, the densities inside a normal walled building and at outdoor sites without vegetation, the microclimate conditions of both of which were different from the outdoor sites with vegetation, were low. To evaluate the effect of blocking by walls for Ae. albopictus invading to feed, an additional experiment by using a bamboo hut with openings of different sizes in the walls was conducted in Thailand. As the opening in the walls was smaller, the difference in the number of females between inside and outside of the hut became significantly larger. Therefore, the effect of physical blocking by walls was suggested. We proposed the presence of vegetation, the difference in environmental conditions inside buildings from those in vegetation due to blocking, and physical blocking by walls for invasion as ecological factors influencing the exophagy of Ae. albopictus. (author abst.

How Zoophilic Japanese Encephalitis Vector Mosquitoes Feed on Humans

金沢大学理工研究域自然システム学系Japanese encephalitis virus (JEV) is the most frequent cause of mosquito-borne encephalitis in Asian countries. Several culicine species are potential vectors. The primary JEV vectors feed mainly on cows (a dead-end host for JEV), pigs (an amplifying host), and, occasionally, humans (a dead-end host). It is essential to determine blood-feeding patterns to understand the transmission cycle of the disease. Here we review blood-feeding characteristics of the primary JEV vectors Culex tritaeniorhynchus, Culex vishnui, and Culex gelidus based on experimental works and field surveys conducted in Asian countries. Several studies showed that these JEV vectors have an innate preference for cows; however, the former two species often showed higher rates of blood-feeding on pigs than on cows, probably because pigs are more abundant than cows. On the other hand, the latter species Cx. gelidus fed mostly on cows. Thus, the first two species showed higher plasticity to compromise host availability than the last. By reviewing the available articles and based on our relevant studies, it may be deduced that JEV transmission cannot be reduced by zooprophylaxis. We emphasize the need of keeping cows away from the human residences to dampen the human risk of JEV. These primary JEV vector species exhibit pre-biting resting. The adaptive significance of this behavior remains to be unexplored, but it may have a function to avoid defensive attack of host animals. Application of recent quantitative analysis of gene expression in this phase may enable us to come up with novel vector control strategies. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: [email protected] Period 12 month

Life history effects of prey choice by copepods: implications for biocontrol of vector mosquitoes

Macrocyclops distinctus, Megacyclops viridis, and Mesocyclops pehpeiensis, which are common in rice fields during the summer season in Nagasaki, Japan, showed variable potentialities as biological control agents of larval Aedes albopictus, Culex tritaeniorhynchus, and Anopheles minimus in the laboratory. Macrocyclops distinctus and M. viridis, the largest copepod species, had fewer eggs within an egg clutch in nature than the smallest species, M. pehpeiensis, which also had a lower developmental time for sexual maturation (based on the appearance of the 1st clutch). Longevity as well as fecundity were influenced by nutritional conditions and varied significantly between the species. All species had shorter life spans when starved, but resistance to starvation was more pronounced in the larger species. All the species had lower clutch production when starved. Also, although the frequency of clutch production was high in M. pehpeiensis (M. pehpeiensis produced a clutch every 2 days, whereas M. distinctus and M. viridis took on average almost 3 days), total clutch production was far higher in the larger species. The copepods fed readily on mosquito larvae, with M. distinctus and M. viridis killing fewer Ae. albopictus than M. pehpeiensis, which, however, killed fewer An. minimus. These copepods exhibited a similar and limited predation against Cx. tritaeniorhynchus. Results of our study support the contention that these copepods have the potential to be used as biological control agents of immature mosquitoes. Also, our results give useful information on colony maintenance and field introduction. In particular, releasing copepods with Paramecium as food could increase their survival in the habitat of the targeted pest

Influence of the Distribution of Host Species on Adult Abundance of Japanese Encephalitis Vectors Culex vishnui Subgroup and Culex gelidus in a Rice-Cultivating Village in Northern Vietnam

A field study was conducted in a village in northern Vietnam to investigate how host distribution influences Japanese encephalitis (JE) vector abundance. Indoor and outdoor collections were conducted from 50 compounds. We collected three JE vector species--Culex tritaeniorhynchus and Culex vishnui that comprised the Culex vishnui group and Culex gelidus. Spatial autocorrelation was not observed in the mosquito assemblies at any scale larger than the house compounds. Multivariate analyses revealed that the Cx. gelidus density correlated positively with both the host proximity to the breeding sites and cattle density; however, the Cx. vishnui subgroup density correlated positively only with cattle density. These results showed that the number of cattle in a compound influenced the JE vector abundance in that compound, and the abundance of Cx. gelidus, not of the Cx. vishnui subgroup, was affected by the host proximity to the breeding sites in the village

Host-feeding patterns of Culex tritaeniorhynchus and Anopheles sinensis (Diptera: Culicidae) in a ricefield agroecosystem.

金沢大学理工研究域　自然システム学系水田発生性蚊類成虫の吸血選択を調べるために, 佐賀県西有田町で1996及び1997年の5月から9月に成虫採集を行った。ドライアイス付加ライトトラップと吸虫管により合計31,804頭のコガタアカイエカとシナハマダラカ雌成虫を採集した。調査したすべての牛舎と豚舎ではライトトラップ採集により多数の成虫が捕獲されたが(牛舎7,933,豚6,441,鶏舎5,267), 鶏舎では吸血蚊がほとんど採集されなかった。コガタアカイエカとシナハマダラカの吸血率は, 牛舎と豚舎ではそれぞれ62%(N=7,113), 74%(N=7,261)であったが, 鶏舎では5%以下(N=5,267)であった。ELISAによる吸血源同定の結果, 両種とも鶏よりも牛と豚を選択していることが示された。また, 牛舎と隣接した鶏舎から採集された吸血蚊も90%以上(N=143)が牛を吸血していた。鶏よりも豚と牛から吸血する傾向は採集場所(棚田周辺か平野部), 採集方法(ライトトラップか吸虫管)を問わず観察された。 Adults of rice-field mosquitoes were collected between May and September of 1996 and 1997 in Nishi Arita, Saga Prefecture, Japan, to determine their feeding pattern in an area where animals were available in large numbers. In total, 31,804 female Culex tritaeniorhynchus and Anopheles sinensis were collected from animal sheds using dry ice-baited light traps and mouth aspiration. Light traps in all the animal sheds captured large numbers of mosquitoes (cowsheds 7,933,pigsties 6,441 and chicken sheds 5,267 mosquitoes), although few fed upon the chickens. Overall, 62% (N=7,113) of fed Cx. triaeniorhynchus and 74% (N=7,261) of An. sinensis were caught by light traps at the cowsheds and pigsties compared to less than 5% (N=5,267) at the chickens sheds. The type of animal in the shed was the most important factor determining the feeding rates. Blood-meal identification by direct ELISA indicated that both Cx. tritaeniorhynchus and An. sinensis preferred cows and pigs to chickens. Over 90% (N=143) of the fed mosquitoes collected from one chicken shed had fed upon cows in an adjoining cowshed. The tendency to feed upon cows and pigs more than on chickens was observed both in the hillside (terraced) and lowland ricefields. This trend is shown in the results obtained by both the aspirator and light trap collection methods

Association between Optic Nerve Head Microcirculation and Macular Ganglion Cell Complex Thickness in Eyes with Untreated Normal Tension Glaucoma and a Hemifield Defect

Purpose. We evaluated the association between optic nerve head (ONH) microcirculation and macular ganglion cell complex (mGCC) thickness in patients with untreated normal tension glaucoma (NTG) and a hemifield defect. Methods. The medical records of 47 patients with untreated NTG were retrospectively reviewed. Laser speckle flowgraphy was used to obtain mean blur rate (MBR), a relative measure of blood flow. Average total deviation (TD), mGCC, and the circumpapillary retinal nerve fiber layer (cpRNFL) thickness were also analyzed. Results. All parameters corresponding to the defective hemifield were significantly lower than those corresponding to the normal hemifield. In the defective hemifield, MBR was correlated with TD, mGCC, and cpRNFL thickness. In the normal hemifield, MBR was only correlated with mGCC thickness, and multiple regression analysis showed that mGCC thickness was a significant contributing factor of the MBR. Conclusion. MBR was well correlated with mGCC thickness in eyes with untreated NTG and a hemifield defect. In the normal hemifield, mGCC thickness was a contributing factor of the MBR indicating that ONH circulatory dysfunction may be associated with retinal structural changes in the early stages of glaucoma. A reduction in ONH microcirculation may be an early indicator of the presence and progression of glaucoma

Long-term monitoring on the dynamics of ecosystem CO2 balance recovering from a clear-cut harvesting in a cool-temperate forest

Clear-cut harvesting is one of the important types of forest management but is considered to be a large CO2 source to the atmosphere. Understanding how this form of logging affects a site’s CO2 balance is critical for determining appropriate management scenarios, yet we have little understanding of how wood harvesting affects the ecosystem CO2 balance. An experimental clear-cutting and plantation establishment study has been conducted in a cool-temperate mixed forest in northern Japan to obtain a complete series of pre- and post-harvest data on the net ecosystem CO2 exchange (NEE) between the ecosystem and the atmosphere until a disturbed ecosystem once more become a net CO2 sink in the annual budget and recapture all the emitted CO2 after the harvest. A mixed forest, which had been a weak CO2 sink, was disturbed by clear-cutting and was replaced with a hybrid larch (Larix gmelinii × L. kaempferi) plantation. The ecosystem turned to be a large CO2 source just after the harvesting in 2003, and the cumulative net CO2 emission reached up to 15.4 MgC ha–1 at 7 years after the harvesting, then the ecosystem turned to be a CO2 retrieve mode (CO2 sink in the annual budget). This ecosystem recaptured all CO2 emission 18 years after the harvesting in 2020, if off-site carbon storage in forest products is not considered. This implies one harvesting operation cause large invisible and long-lasting effect on the forest ecosystem CO2 balance