マメコバチを加害する労働寄生性コナダニ類2種の繁殖戦略 : II.生活史,便乗部位,発育および繁殖

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Two astigmatid mites, Chaetodactylus nipponicus and Tortonia sp. are sympatrically distributed in Japan. Both species usually occur in the same host nests, but coinhabiting in the same cells was rarely found. As the second report, mechanisms 1) to determine the ratio of different hibernating stages, and 2) to inhibit coinhabiting of 2 mite species in the same host cells are studied. Field data were obtained from nests of Osmia cornifrons withdrawn from apple orchards in central and northern Japan in the winter between 2000 and 2001. Development and fecundity and other related data were obtained by rearing of mites at various temperatures in the laboratory. Life cycle of the 2 mite species consists of 3 phases, i.e., initial reproductive phase (1), multiple reproductive phase (II) and overwintering phase (III). In C. nipponicus, 2 different morphs of deutonymphs, phoretic and cyst-like, were recognized as hibernatihg stages, the former most abundant. On the other hand, in Tortonia sp. 5 hibernating stages (larva, protonymph, phoretic deutonymph, tritonymph and adult) were found. Duration from egg to adult at 28℃ in phase II was about 10 days in C. nipponicus, but it was about 15 days in Tortonia sp. Five to six generations were repeated in one pollen loaf. In C. nipponicus, 40-53 individuals of the 2 morphs of deutonymphs were produced by one mg of pollen mass. Sex ratio in adults was approximately 0.5 in both species of mites, irrespective of their ancestral stages. The total number of eggs laid per female in phase II was 234.3±48.2 (N= 12) in C. nipponicus, and 292.9±44.2 (N=15) in Tortonia sp. Fecundity was differed according to the ancestry in C. nipponicus, thus, the total number of eggs laid per female molted from the phoretic deutonymphs was 5 times that from the cyst-like duetonymphs. Intrinsic rate of natural increase (r) of C. nipponicus was much higher than that of Tortonia sp., reflecting the remarkable difference of the number of eggs laid/female/day between the mite species. Tortonia sp. was always expelled by C. nipponicus through a remarkable difference of the values of e' (e=Napier's number) for 4 months, when they invaded the same host cells. However, in those cells whose hosts were living, the ratio of individual numbers of Tortonia sp. was higher than that of C. nipponicus, because the former can survive by feeding on host feces. In C. nipponicus, 2 morphs of deutonymphs seem to be produced, when the amount of residual pollen loaf consumed by mites reached critical volume. Those protonymphs, which ate much pollen, became phoretic deutonymphs and the less-fed became cyst-like deuto-nymphs. In Tortonia sp., those individuals which are able to feed on pollen developed into adults, but others seem to be obliged to cease their development. Protonymphs of Tortonia sp. that encountered shortage of food seem to molt as phoretic deutonymphs. The cyst-like deutonymphs in C. nipponicus and the phoretic deutonymphs in Tortonia sp. are thus regarded as hunger typed (starved) stages, respectively.
日本昆虫学会の論文
2003-06-25

マメコバチを加害する労働寄生性コナダニ類2種の繁殖戦略 : II.生活史,便乗部位,発育および繁殖

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