|Budget Amount *help
¥1,600,000 (Direct Cost : ¥1,600,000)
Fiscal Year 1994 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1993 : ¥800,000 (Direct Cost : ¥800,000)
Factors affecting on the induction and survival of infective juveniles(IJ) of entomopathogenic nematode Steinernema carpocapsae were investigated in vivo and in vitro. (1)A successive transfer of gravid females of the lst generation onto fresh dog food agar plates resulted in a continuous occurrence of large lst generation-type adults. This result clearly indicate that the development from the lst to the 2nd generation adults whose progenies develop into IJ nuder crowding and/or food-shortage, is not only genetically controlled but also regulated by environmental conditions. (2)In a liquid medium for the free-living nematode Caenorhabditis elegans, S.carpocapsae developed very slowly, became adults small in size, and produced a few numbers of IJ.An addition of sterilized lepidopterous insect larvae, which had been killed by S.carpocapsae inoculation 1 day before addition, highly improved medium quality : gravid females produced eggs profoundly, nematode population size increased steadily with time, and many IJ appeared. These results indicate that IJ are induced without participation of symbiotic bacteria wtich change their from from phase I to phase II,although the phase transformation has been thoughe to play roles in IJ formation. (3)Oral administration of axnic nematodes into axnic larvae of Galleria mellonella and Spodoptera 1itura resulted in host death, without causing drastic breakdown of host tissues and organs. However, the development of nematodes cultured axnically was far inferior to the nematodes cultured monoxenically.From an evolutional viewpoint, S.carpocapsae is considered to be on the midway from bacteriophagous free-living life to true parasite via bacteria-assisted parasitic life. (4)No positive correlation was found between nematode survivability and coiling, which is an adaptive behavior for decreasing water loss by reducing body surface exposed to environment.