Search

Some members of the genus Spiroplasma are vertically transmitted endosymbionts of insects. Among them, Spiroplasma sp. Dhd, a member of the Spiroplasma poulsonii clade, is highly prevalent among worldwide populations of Drosophila hydei. Here we found that 53 out of 3,763 wild-caught D. hydei (1.4 %) were ectoparasitized by the mite that belong to the genus Macrocheles. Many of the ectoparasitized flies (79 %) had a single mite, but some flies had up to five mites. Among 59 mites subjected to Spiroplasma-specific PCR, 15 individuals were found to be positive. Infection status of Spiroplasma in flies and the associated mites were incongruent. Partial nucleotide sequences of the Spiroplasma P58 gene suggest that some of the mites are infected with a Spiroplasma, which is identical or closely related to Spiroplasma sp. Dhd. This finding provides a potential route of horizontal Spiroplasma transmission between D. hydei individuals in natural populations. In addition, a Spiroplasma strain that does not form a monophyletic group with S. poulsonii was also found from a mite individual. [ABSTRACT FROM AUTHOR]

A bacterium belonging to the genus Spiroplasma, an endosymbiont of the fly Drosophila hydei, is vertically transmitted through host egg cytoplasm. To infer vertical transmission rates of Spiroplasma in natural populations of D. hydei, the infection status of Spiroplasma was examined for offspring produced by Spiroplasma-positive females that were collected in two geographical populations. In both populations, nearly half of the broods consisted of only infected offspring. Infection frequencies of the rest of the broods ranged from 0.364 to 0.975. Quantitative PCR demonstrated that the Spiroplasma titers in the whole body of wild-caught females were highly variable (1.81 × 10-5.60 × 10 cells per insect). Contrary to our expectations, however, the Spiroplasma titers did not account for the variation in infection frequencies among offspring (i.e., vertical transmission rates). These results suggest that the spatial distribution of Spiroplasma, particularly in somatic tissues and germ tissues, is highly variable among host individuals, which may be caused by environmental stochasticity or some unknown effects. [ABSTRACT FROM AUTHOR]

In a previous study, we showed that Spiroplasma, a maternally transmitted endosymbiotic bacterium of Drosophila hydei, enhances larval to adult survival of its host when exposed to oviposition attack by the parasitoid wasp Leptopilina heterotoma. The mechanism by which Spiroplasma enhances host survival has not been elucidated. To better understand this mechanism, we compared the growth of wasp larvae in Spiroplasma-infected and uninfected hosts. Our results indicate that wasp embryos in Spiroplasma-infected hosts hatch and grow normally for ~2 days, after which their growth is severely impaired, compared to wasps developing in uninfected hosts. Thus, despite their reduced ability to complete development in Spiroplasma-infected hosts, developing wasps may exert fitness costs on their hosts that are manifested after host emergence. The severity of these costs will influence the degree to which this protective mechanism contributes to the long-term persistence of Spiroplasma in D. hydei. We therefore examined survival to 10-day-old adult stage and fecundity of Spiroplasma-infected flies surviving a wasp treatment. Our results suggest detrimental effects of wasp attack on longevity of Spiroplasma-infected adult flies. However, compared to Spiroplasma-free flies exposed to wasps, Spiroplasma-infected flies exposed to wasps have ~5 times greater survival from larva to 10 day-adult. The relative fecundity of wasp-attacked Spiroplasma-infected females was ~71% that of un-attacked Spiroplasma-free females. Our combined survival and female fecundity results suggest that under high wasp parasitism, the reproductive fitness of Spiroplasma-infected flies may be ~3.5 times greater than that of uninfected females, so it is potentially relevant to the persistence of Spiroplasma in natural populations of D. hydei. Interestingly, Spiroplasma-infected males surviving a wasp attack were effectively sterile during the 3-day period examined. This observation is consistent with the expectation that, as a maternally transmitted symbiont, there is little selective pressure on Spiroplasma to enhance the reproductive fitness of its male hosts. [ABSTRACT FROM AUTHOR]

maternally-inherited spiroplasma endosymbiont of Drosophila hydei does not exert apparent phenotypes on both sexes of its host and is prevalent in natural populations of D. hydei. Our previous experiments using a laboratory stock of D. hydei revealed that low temperatures (such as 15°C and 18°C) dramatically lower the vertical transmission rates of this spiroplasma. Therefore, we hypothesized that, in temperate regions, the infection frequencies may decrease in cool seasons but increase in the summer season. To clarify the temporal population dynamics of the spiroplasma infection, D. hydei were collected from two Japanese populations in 2006-2008 from May to early August, representing the only period when a number of D. hydei are collectable in Japan, and examined for spiroplasma infection. Within each year, the frequency of spiroplasma infection fluctuated considerably in both populations. Consistent with our hypothesis, the infection frequency showed an increasing trend in both populations in 2007. However, the data in 2006 and 2008 did not show consistent patterns of increase. The population dynamics of spiroplasma infection may be affected but not critically determined by temperature. Moreover, despite the fluctuation within each year, the infection frequencies seemed to be stable across the years. The frequencies of spiroplasma infection in D. hydei populations may be stabilized by multiple factors. One of these factors may involve a context-dependent positive effect of spiroplasma on the fitness of D. hydei, as was recently observed in laboratory experiments. [ABSTRACT FROM AUTHOR]

Introduction of two doses of the X-chromosomal wCo duplication next to a normal X-chromosome in males of D. hydei leads to duplication of testis tissue and structures derived from the male genital disc. The effect of this partial hyperploidy of the X-chromosome seems restricted to the male. We tentatively conclude that this part of the X-chromosome contains some factor(s) which may specifically affect the reproductive system and analia of males. [ABSTRACT FROM AUTHOR]

The bristle pattern along the anterior margin of Notch (N1-22.3) wings of Drosophila hydei and the occurrence of yellow ( y 1-38.8) marked clones induced by X-ray irradiation during various larval stages are described. Unirradiated N/N wings show gaps ('notches') in the longitudinal bristle rows along the 1st longitudinal vein, with tufts of bristles particularly near gaps. X-ray irradiation increases the number and total length of the gaps. The patterning of bristles along the margin depends on the N genotype of the induced clones. Recombinant N/ N clones from irradiated wings show excessive growth with an autonomous wildtype bristle pattern. Characteristically, these clones do not respect the dorso-ventral compartment boundary along the wing margin, do not follow an exponential (2) growth pattern, tend to fill the gaps with bristles and their yellow medial row bristles are less often interspersed with y bristles than described for N/ N wings. Homozygous N appears to be a cell lethal condition in D. hydei as it is in D. melanogaster. When y clones were kept phenotypically Notch (viz., N/N/N) as the background cells, we found a lower number of y bristles, a lower percentage of mosaic wings but also a reltive deficiency of y interspersions. The latter is discussed in relation to a possible clonal originof the notches. [ABSTRACT FROM AUTHOR]

The bristle pattern along the first longitudinal vein of the wing of D. hydei differs from that of D. melanogaster. Instead of a triple row, D. hydei and some allied species show a pattern of five parallel bristle rows of which the medial row (MR) is comparable to the medial triple row (MTR) of D. melanogaster. Cells of the MR can be made homozygous yellow (y) by induction of mitotic recombination in heterozygous y/y females. Until 70 h after egg laying (AEL), the MR clones in D. hydei overlap with one or more of the accompanying dorsal and ventral bristle rows. Between 70 and 120 h AEL the MR clones only overlap with dorsal bristle rows. Some time later they also become separated from both dorsal rows. The resulting MR clone pattern fits with the overall longitudinal clone pattern in the wing blade of D. melanogaster described by Bryant (1970) and others. The MR clones in D. hydei, however, often show a fragmented appearance with many indentations of the surrounding y tissue even when induced after fixation of the DV compartment boundary. This result contrasts with the commonly held notion, derived from work with D. melanogaster, that compartment boundaries are smooth lines. [ABSTRACT FROM AUTHOR]

In a white-eyed attached-X chromosome of Drosophila hydei, C(1)RM, w ·w (homozygous for whiteivory), a spontaneous mutation occurred of w to w83. Dominance order is w> w83> w, where w83· w83 homozygotes are indistinguishable from w83· w heterozygotes. The frequency at which in heterozygotes these alleles become homozygous by recombination (homozygosis frequency) was investigated by a progeny test. For any locus situated at least 50 map units away from the centromere, the theoretical homozygosis frequency should be 16.6%. This value was approximated by our results. However, by selecting heterozygous females over eight generations, we observed an unexpected decline in homozygosis frequency as selection progressed. In parallel, the proportion of males substantially increased throughout the experiment. [ABSTRACT FROM AUTHOR]

Four cell lines have been isolated from Drosophila hydei embryos. Three lines have a normal XY karyotype, the fourth has an XO karyotype with an additional small heterochromatic fragment. The cells contain presumable cytoplasmic virus like particles. [ABSTRACT FROM AUTHOR]