Two new microsporidia, Anostracospora rigaudi n. g., n. sp., and Enterocytospora artemiae n. g., n. sp. infecting the intestinal epithelium of Artemia parthenogenetica Bowen and Sterling, 1978 and Artemia franciscana Kellogg, 1906 in southern France are described. Molecular analyses revealed the two species belong to a clade of microsporidian parasites that preferentially infect the intestinal epithelium of insect and crustacean hosts. These parasites are morphologically distinguishable from other gut microsporidia infecting Artemia. All life cycle stages have isolated nuclei. Fixed spores measure 1·3×0·7 μm with 5-6 polar tube coils for A. rigaudi and 1·2×0·9 μm with 4 polar tube coils for E. artemiae. Transmission of both species is horizontal, most likely through the ingestion of spores released with the faeces of infected hosts. The minute size of these species, together with their intestinal localization, makes their detection and identification difficult. We developed two species-specific molecular markers allowing each type of infection to be detected within 3-6 days post-inoculation. Using these markers, we show that the prevalence of these microsporidia ranges from 20% to 75% in natural populations. Hence, this study illustrates the usefulness of molecular approaches to study prevalent, but cryptic, infections involving microsporidian parasites of gut tissues.

Divergence between populations sharing the same habitat can be initiated by different reproductive times, leading to allochronic differentiation. A spatially localized allochronic summer population (SP) of the pine processionary moth Thaumetopoea pityocampa, recently discovered in Portugal, occurs in sympatry with the local winter population (WP). We examined the level of genetic differentiation between the two populations and estimated the current gene flow within the spatial framework of their co‐occurrence. Mitochondrial data indicated that the two sympatric populations were genetically closer than other WP populations. Conversely, microsatellite genotyping uncovered greater differentiation between the two sympatric populations than between allopatric ones. While male trapping confirmed that reproduction of SP and WP occurred at distinct times, clustering approaches demonstrated the presence of a few LateSP individuals emerging within the WP flight period, although genetically identified as SP. We also identified rare recent hybridization events apparently occurring mainly in the margins of the current SP range. The ongoing gene flow detected between the ancestral and the emerging allochronic populations revealed an incomplete reproductive isolation, which must therefore be taken into account and integrated with studies focussed on ecological drivers, so that a complete understanding of the ongoing speciation process might be achieved.

Ageing results from the accumulation of multifactorial damage over time. However, the temporal distribution of this damage remains unknown. In seasonal species, transitions between seasons are critical periods of massive physiological remodelling. We hypothesised that these recurrent peaks of physiological remodelling are costly in terms of survival. We tested whether captive small primates exposed to an experimentally increased frequency of seasonal transitions die sooner than individuals living under natural seasonality. The results show that experiencing one additional season per year increases the mortality hazard by a factor of 3 to 4, whereas the expected number of seasons lived is only slightly impacted by the seasonal rhythm. These results demonstrate that physiological transitions between periods of high and low metabolic activity represent a major mortality risk for seasonal organisms, which has been ignored until now.