Satellite DNAs are the major repetitive DNA components in eukaryotic genomes. Although satellite DNA has long been called "parasite DNA" there is substantial evidence that it could be associated with some functions of chromosome biology. Ladybird beetles (Coccinellidae) are one of the largest and most important groups of beetles. Many ladybirds are of economic interest as biological control agents because they eat some agricultural pests such as aphids and scale insects. However, other species are phytophagous and can damage crops. Despite the ecological importance of the latter group there are no studies on their satellite DNA. A satellite DNA family was isolated and characterized in the ladybird Henosepilachna argus. This satellite DNA is organized in tandem repeats of 658 bp and is A + T rich (67.3%). The recorded high sequence conservation of the monomers together with the detection of putative gene conversion processes indicate concerted evolution. Reverse transcription polymerase chain reaction (RT-PCR) revealed that this satellite DNA is transcribed and in situ hybridization its location in the subtelomeric regions of all chromosomes except the long arm of the X chromosome. The presence of this satellite DNA in other species of the genus Henosepilachna and Epilachna was also tested using PCR. The results indicate that this satellite DNA sequence is so far specific to H. argus., Pablo Mora, Jesús Vela, Areli Ruiz-Mena, Teresa Palomeque, Pedro Lorite., and Obsahuje bibliografii
The incidence of sibling cannibalism in clutches of Harmonia axyridis infected by the male-killing Spiroplasma was compared with that in uninfected clutches, and the way in which fitness compensation was realized by sibling cannibalism was investigated. Primarily the rate of sibling cannibalism was determined by the hatching rate as all unviable eggs were consumed both in infected and uninfected clutches. Per capita consumption of roughly 0.1 individuals was estimated for uninfected clutches in the present study, as compared to 0.3 individuals in previous studies. The per capita consumption in infected clutches was 1.4, showing that the male-killing behavior of the Spiroplasma provides an approximately 4-14 fold increase in the chance of sibling cannibalism. Both in infected and uninfected clutches, the median of the starting time of sibling cannibalism was soon after that of the completion of hatching. Larvae started to disperse from their egg clutches only about 7.5-8.5 h after the initiation of hatching. These time sequences indicate that sibling cannibalism occurs at the earlier stage of the hatching process and the density of aphids in the area has little or no influence on incidence of the sibling cannibalism. During the maintenance of the infected line for five generations, exclusively females were produced and the median of the hatching rate was 0.395, suggesting a very high rate of vertical transmission of the Spiroplasma infection. Although the measurement of other parameters, such as the effect of Spiroplasma infection on fecundity or longevity, are necessary, the high compensation rate shown in the present study, together with the very high vertical transmission, may explain the prevalence of the present male-killing agent in the local populations of the ladybird beetle.
The ladybird beetle, Cheilomenes sexmaculata (Fabricius), has been extending its distribution in and around urban areas at higher latitudes in Japan over the past 100 years. Between 2003 and 2011, we investigated the seasonal occurrence, aphid prey and population dynamics of this species in an urban park in Osaka City, central Japan. We found that C. sexmaculata completes three generations a year in Osaka. Overwintered adults emerge in March or April and produce two (or rarely one) generations by summer. Second-generation adults aestivate and subsequently produce another generation in autumn. This species feeds on five species of aphids that infest planted shrubs and alien weeds throughout the vegetative season. We analyzed the association between accumulated temperature and when overwintered adults first emerged. In addition, we determined the association between their time of emergence, peak abundance and last occurrence, and meteorological conditions. There was no association between the sum of effective temperatures and termination of adult overwintering. There was, however, an association between first occurrence and peak abundance, and climatic conditions, such as warm temperatures or low humidity. This species maintained a stable population in an urban park by becoming quiescent when climatic conditions were unfavourable or prey was scarce. We discussed these findings in relation to urban environmental factors, such as climate, food conditions and vegetation., Yasuko Kawakami, Kazuo Yamazaki, Kazunori Ohashi., and Obsahuje bibliografii