ABSTRACT. Several species of birds in Minami Daito Island, an oceanic island located in the far south from the main islands of Japan, were found to be infected with avian Plasmodium. However, no vector species of the avian malaria in this island have been revealed yet. To speculate potential vectors, we collected mosquitoes there and investigated using a PCR procedure whether the mosquitoes harbor avian malaria or not. Totally 1,264 mosquitoes including 9 species were collected during March 2006 to February 2007. The mosquitoes collected were stored every species, sampled date and location for DNA extraction. Fifteen out of 399 DNA samples showed positive for the partial mtDNA cytb gene of avian Plasmodium. Estimated minimum infection rate among collected mosquitoes was 1.2% in this study. Four species of mosquitoes; Aedes albopictus, Culex quinquefasciatus, Lutzia fuscanus and Mansonia sp. had avian Plasmodium gene sequences. Detected DNA sequences from A. albopictus and L. fuscanus were identical to an avian Plasmodium lineage detected in bull-headed shrike (Lanius bucephalus) captured in the island. Different sequences were detected from C. quinquefasciatus, which were corresponding to an avian Plasmodium from a sparrow (Passer montanus) and Plasmodium gallinaceum. Our results suggest that A. albopictus, Lutzia fuscanus, C. quinquefasciatus, and Mansonia sp. could be potential vectors of avian malaria in Minami Daito Island. This study was the first report of molecular detection of avian Plasmodium from mosquitoes in Japan.

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The effects of pC% were investigated by changing the aeration rate, the purging gas and the total pressure in a chemostat cultivation. Under glucose supply limitation, an increase in pCO2 from 44 kPa to 195 kPa resulted in 25 % decrease in cell concentration, 8 % increase in ethanol concentration, and 50 % decrease in glycerol concentration. Under oxygen supply limitation, similar dependency of ethanol and glycerol on pC@ was observed, however, no influence of pCO2 on the cell yield was observed. The change in ethanol yield by pC@ appeared to be caused by the equilibrium shift of pyruvate dehydrogenase system. IntroductionThe effects of C@ on yeast growth and metabolism have been studied from various aspects as reviewed by Jones and Greenfield (1982). Increases in pCo;! resulted in decreases in the cell yield and growth rate of yeast Saccharomyces in baker's yeast production (Chen and Gutmanis, 1976) and beer fermentation (Nakatani, et al. 1984;Knatchbull and Slaughter, 1987), although little changes in fermentation activity due to pC@ change were observed. However, no papers have reported about the effects of pC@ on the ethanol yield. Norton and Krauss (1972) showed that the cell growth stopped at 280 kPa of C@ pressure metabolically produced during ethanol fermentation, but a culture pressurized at 280 kPa using N2 gas did not reduce the cell growth rate. On the contrary, Macy and Miller (1983) showed that under stringently controlled anaerobic cultivation, C@ purged culture showed a shorter initial lag than N2 purged culture. These results suggest that the effect of Co;! on cell growth is related to the biological state affected by oxygen, such as the fatty acid composition of the membrane lipid. The effects of C@ on cell physiology reported so far were investigated under batch fermentation, where the concentrations of oxygen and other nutrients changed significantly during the cultivation period.

ABSTRACT. Haemosporidian parasites infection among wild birds inhabiting Minami-daito Island was studied. Blood films from 183 birds representing 4 species of 4 families were examined microscopically. Avian haemosporidian parasites were detected in 3 species with an overall prevalence of 59.6%. None of the 30 Daito scops owls (Otus scops interpositus) examined were infected. Either Haemoproteus sp. or Plasmodium sp. infection was found in 14 of 31 (45.2%) Borodino islands white-eyes (Zosterops japonicus daitoensis). Plasmodium spp. were found in 94 of 102 (92.2%) bull-headed shrikes (Lanius bucephalus) and 1 of 20 (5%) tree sparrows (Passer montanus). KEY WORDS: Haemoproteus, Minami-daito island, Plasmodium.

Sex allocation theory predicts that parents bias the offspring sex ratio strategically. In avian species, the offspring sex ratio can be biased at multiple growth stages, although the mechanisms are not well known. It is crucial to reveal a cause and timing of biased offspring sex ratio. We investigated (i) offspring sex ratio at multiple growth stages, from laying to fledging; and (ii) the stage at which offspring sex ratio became biased; and (iii) the cause of biased offspring sex ratio in Eurasian tree sparrows Passer montanus. Sex determination of 218 offspring, including hatchlings and unhatched eggs from 41 clutches, suggested that the offspring sex ratio was not biased at the egg‐laying stage but was significantly female‐biased after the laying stage due to higher mortality of male embryos. Half of the unhatched eggs showed no sign of embryo development (37/74, 50.00%), and most undeveloped eggs were male (36/37, 97.30%). Additional experiments using an incubator suggested that the cause of embryo developmental failure was a lack of developmental ability within the egg, rather than a failure of incubation. This study highlights the importance of clarifying offspring sex ratio at multiple stages and suggests that offspring sex ratio is adjusted after fertilization.

SummaryThe introduction of exotic rats Rattus spp. is one of the most important factors contributing to the reduction in avian diversity and extinctions on oceanic islands. However, little is known about factors other than predation, which are associated with the loss of island biodiversity. We report that introduced Ship Rats Rattus rattus constructed arboreal dome-shaped nests and secondarily used open-cup nests of the Bull-headed Shrike Lanius bucephalus for roosting or rearing young in trees within hedgerows along sugarcane fields of Minami-daito Island (northwest Pacific). We found that temporal nest utilization by Ship Rats forced Bull-headed Shrikes to abandon their nests before egg-laying. We suggest that kleptoparasitism applies to the interaction between Bull-headed Shrikes and Ship Rats, which usurp shrike nests during their breeding period. It is necessary to consider the potential effects of introduced Ship Rats on insular avian communities not only through predation but also through interspecific interaction over nest-sites.

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