富山大学理学部生物学科

生物学科セミナー「Wolbachia Bacteria of Arthropods: Phylogenetic Relationship, Relative Density and Host Effects」(Dr. Itsanun Wiwatanaratanabutr, King Mongkut’s Institute of Technology Ladkrabang, Asst. Prof.)(2017年8月2日開催)のご案内

生物学科セミナー

日時:2017年8月2日(水) 13時から(1時間程度)

場所:理学部棟C203室

演者:Dr. Itsanun Wiwatanaratanabutr(King Mongkut’s Institute of

Technology Ladkrabang,  Asst. Prof.)

要旨:

Wolbachia are a group of maternally-inherited, intracellular, alpha

Proteobacteria that are widespread among arthropod hosts. They are

capable of inducing a range of reproductive abnormalities in their hosts

including cytoplasmic incompatibility (CI) and feminization. An approach

to defining the phylogenetic relationships among these endosymbionts in

arthropods using groE gene sequences was reported. Wolbachia strains

from tropical insects and isopod crustaceans were first classified into

supergroups using groE sequences. The distribution and diversity of

Wolbachia infection in isopods and copepods in Thailand were first

surveyed in this study. Two Thai isopod species were infected by

Wolbachia. The relative densities of Wolbachia among each life cycle

stage both in mosquito, Aedes albopictus and in copepod, Mesocyclops

thermocyclopoides in terms of temperature and crowding effects were

compared using real-time quantitative PCR assay. These two species are

known to be superinfected with both A- and B- supergroup Wolbachia.

Higher numbers of mosquito larvae and copepod nauplii in rearing

condition caused lower densities of both Wolbachia strains. The effect

of temperature on Wolbachia also revealed a significant decrease in

density following exposure to elevated temperature (37℃) in both sexes

of these two species. The effects of insecticide (temephos) exposure

during larval development were examined in Wolbachia-infected and

uninfected strains of Ae. albopictus. The same methods were also used in

the copepod, M. aspericornis, which is the predator of mosquito larvae.

Stress was measured in terms of survival, development time and wing size.

 Temephos did not have any effects on copepods. A high concentration of

temephos was associated with a reduction in survival rate and wing

length but did not affect development time and Wolbachia density in both

sexes of mosquitoes. Mating, oviposition and host-seeking behavior of

Wolbachia-infected and uninfected Ae. albopictus were compared. Mating

success of infected males was significantly higher than mating success

of uninfected males when mated with both infected and uninfected females.

 Therefore, Wolbachia infection may influence the reproductive behavior

of mosquito. There were no clear differences in oviposition responses

between mosquito strains with all strains ovipositing significantly more

on hay infusion and larval rearing water than on water controls and less

on 4-methylphenol. Aedes albopictus differed in host-seeking responses

to an arm, acetone, CO2 and dichloromethane with significant difference

between strains.

 

世話人:土田努(理学部生物学科 准教授)

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