Under seasonal conditions, Polydesmus angustus individuals born in the first part of the breeding season have a 1-year life cycle and those born later have a 2-year life cycle (cohort-splitting). In this study, 249 juveniles from four early broods (born in mid-July) and four late broods (born in September) were reared under similar laboratory conditions, to test for possible maternal influences on life-cycle duration. Development times of early- and late-born individuals were compared under four combinations of day length and temperature (16 h - 18°C, 16 h - 16°C, 12 h - 18°C and 12 h - 16°C). The results showed that development time varied significantly in response to day length, temperature and sex, but that of individuals in the early and late broods did not differ significantly (mean development times ± SE: 180 ± 6 and 183 ± 8 days, respectively). There were no significant interactions between birth period and other factors, indicating that the effects of day length, temperature and sex on development time were similar in early- and late-born individuals. This indicates that the extended life cycle of millipedes born late in the season is not maternally determined and that cohort-splitting is controlled entirely by the environmental conditions experienced by the offspring during their development. This conclusion is supported by the absence of significant variation in offspring live weight at birth measured at different times in the breeding season. The results are discussed in relation to the bet-hedging theory, which is often put forward to account for cohort-splitting in arthropods. In P. angustus, the results are consistent with either bet-hedging or adaptive plasticity, but further studies are required to decide which interpretation is correct. and Jean-François David, Jean-Jacques Geoffroy.
1_Maternal and grand-maternal photoperiodic responses of Trichogramma buesi, T. embryophagum, T. evanescens, T. piceum, T. principium, and T. telengai were investigated in laboratory conditions. During the experiment, grand-maternal and maternal generations developed at 20°C and one of the 4 photoperiodic regimes: L : D = 12 : 12, 14 : 10, 16 : 8, and 18 : 6 (in total, 16 combinations) while the progeny developed at L : D = 12 : 12 and one of the 3 thermal regimes: 13, 14, and 15°C. The proportion of diapausing individuals in the progeny of all the studied species was significantly dependent on the direct influence of temperature and on the maternal photoperiodic response. The influence of the photoperiodic conditions during development of the grand-maternal generation was statistically significant in 5 of the 6 studied species, being relatively weak in T. embryophagum and T. telengai, whose geographical ranges extend up to north-western regions of Europe (possibly, these wasps enter diapause so early that the grand-mothers of the diapausing generation develop under long day conditions). Comparative analysis showed that the thresholds of the maternal and grand-maternal photoperiodic responses coincided or almost coincided. The grand-maternal effect was stronger in the progeny of maternal females which developed under short day conditions than in those that developed under long day conditions. This pattern of interaction probably synchronizes the life cycle with seasonal changes because diapause is induced under decreasing day length and thus mothers of diapausing individuals develop at shorter daylength than do grand-mothers., 2_We conclude that the grand-maternal and the maternal effects on Trichogramma progeny diapause are based on one and the same photoperiodic response. In nature, the grand-maternal effect increases the proportion of diapausing individuals in the progeny of females which have developed under short day conditions during two generations, thus achieving a "cumulative" photoperiodic effect., Natalia D. Voinovich, Nina P. Vaghina, Sergey Ya. Reznik., and Obsahuje seznam literatury
Progeny of the flesh fly Sarcophaga bullata exposed to short day length show a maternal effect that prevents the expression of pupal diapause. Although ecological aspects of this effect are well studied, not enough is known about the molecular mechanisms underlying this maternal effect. In this study, two-dimensional electrophoresis was performed to detect differences of the abundance of certain proteins in the ovaries of this fly kept under long day and short day conditions for 2 days after eclosion. Eleven proteins that were abundant and showed significant changes were selected for mass spectrometric identification. Ovary proteins that increased in abundance under short-day conditions were similar to twinstar CG4254-PA, muscle protein 20-like protein, GA13413-PA, gene analogous to small peritrophins (Gasp CG10287-PA) and Ribosomal protein LP1 CG4087-PA. Ovary proteins that decreased in abundance under short-day conditions were similar to the ATP synthase beta subunit, fk506-binding protein and storage protein-binding protein. The 2-D proteome maps included 2 additional unknown proteins that were more abundant and 1 that was less abundant in the ovaries of 2-day old short-day females. Twinstar CG4254-PA, muscle protein 20-like protein and GA13413-PA harbour an actin-binding domain. That the 3 actin-binding proteins increase in abundance suggests that it is likely that an alteration in the actin cytoskeleton is involved in this maternal effect in the flesh fly., Aiqing Li ... [et al.]., and Obsahuje seznam literatury
Maternal effects of heat shock are reported for some species of insects, but little is known about such effects in the western flower thrips (WFT) Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). WFT is a pest of vegetables in greenhouses worldwide. It is susceptible to high temperatures in its natural environment and is controlled using heat treatment in China. WFT population growth is suppressed by a brief exposure to a high temperature of 40°C or 45°C in the laboratory. To explore the mechanism by which high temperatures suppress the growth of WFT populations, as well as the effects of multiple heat treatments on WFT, we recorded the duration of development and survival of immature WFT, and the sex ratio (female/male) and fecundity of F1, F2, F3 and F4 adult females that developed after a single heat shock, and those of F2 offspring after a double heat shock. We also recorded the longevity and ovarian structure of adult females of the treated generation (P) and their F1, F2 and F3 offspring after a single heat shock. In addition, we determined whether the effects of a heat shock on second instar nymphs and adults differed. The results indicate that exposure of the parental generation to 41°C or 45°C for 2 h significantly prolonged the duration of development, reduced survival of immature WFT and altered the sex ratio (female/male), longevity and fertility of their adult female offspring. The effects of a heat shock of 41°C persisted for two generations, whilst the effect of heat shock of 45°C persisted for three generations. In addition, double heat shocks had more pronounced effects than a single heat shock. Heat shock administered to second instar nymphs resulted in a decrease in the number of ovarioles, whilst a heat shock administered to adults resulted in ovariole deformity. The maternal effects of heat shock in terms of the biological parameters of WFT, structure and number of ovarioles, are critical in determining the suppression of the growth at high temperatures of WFT populations.