DNA from lake sediments reveals long-term ecosystem changes after a biological invasion

What are the long-term consequences of invasive species? After invasion, how long do ecosystems require to reach a new equilibrium? Answering these questions requires long-term, high-resolution data that are vanishingly rare. We combined the analysis of environmental DNA extracted from a lake sediment core, coprophilous fungi, and sedimentological analyses to reconstruct 600 years of ecosystem dynamics on a sub-Antarctic island and to identify the impact of invasive rabbits. Plant communities remained stable from AD 1400 until the 1940s, when the DNA of invasive rabbits was detected in sediments. Rabbit detection corresponded to abrupt changes of plant communities, with a continuous decline of a dominant plant species. Furthermore, erosion rate abruptly increased with rabbit abundance. Rabbit impacts were very fast and were stronger than the effects of climate change during the 20th century. Lake sediments can allow an integrated temporal analysis of ecosystems, revealing the impact of invasive species over time and improving our understanding of underlying mechanisms.

Mass budget in two high altitude lakes reveals their role as atmospheric PCB sinks

A mass budget of polychlorinated biphenyls (PCBs) was constructed for two altitude lakes located in the French Alps to (i) quantify inward and outward PCB flux over the entire year of 2012, (ii) hierarchize the dominant pathways of PCB transfers, and (iii) evaluate to what extent these pathways vary between both lakes. The annual PCB inputs were similar, and the glacial runoff and sediment-to-water exchange were negligible sources of PCBs to the water column relative to atmospheric deposition. The annual inputs were primarily introduced by snow deposition and transferred into the lakes during the few weeks of spring thaw. While the dominant deposition pathways were similar, the main processes by which the water column lost pollutants differed between the two lakes. Despite these differences, the mass budget revealed that PCB inputs exceeded outputs for both studied lakes and that the lakes acted as atmospheric PCB sinks for the surrounding mountain environment. The differences in the PCB distribution between the key compartments (sediment and water column) are most likely due to differences in the lacustrine internal processes.

Escape behaviour and ultimate causes of specific induced defences in an anuran tadpole

Induced defences, such as the predator avoidance morphologies in amphibians, result from spatial or temporal variability in predation risk. One important component of this variability should be the difference in hunting strategies between predators. However, little is known about how specific and effective induced defences are to different types of predators. We analysed the impact of both pursuing (fish, Gasterosteus aculeatus) and sit-and-wait (dragonfly, Aeshna cyanea) predators on tadpole (Rana dalmatina) morphology and performance (viz locomotive performance and growth rate). We also investigated the potential benefits of the predator-induced phenotype in the presence of fish predators. Both predators induced deeper tail fins in tadpoles exposed to threat of predation, and stickleback presence also induced longer tails and deeper tail muscles. Morphological and behavioural differences resulted in better escape ability of stickleback-induced tadpoles, leading to improved survival in the face of stickleback predation. These results clearly indicate that specific morphological responses to different types of predators have evolved in R. dalmatina. The specific morphologies suggest low correlations between the traits involved in the defence. Independence of traits allows prey species to fine-tune their response according to current predation risk, so that the benefit of the defence can be maximal.

[Immunoglobulin levels at different ages in the healthy child population]

In this study, we report the IgE, IgA, IgM and IgG levels in the serum and the secretory IgA obtained from a group of children of different ages with normal morphgram, with no personal or family history of allergies and without recurrent infectious diseases. The IgG, IgA and IgM and salivary secretory IgA were determined by the immunonephelometry technique, using specific anti-serum for heavy chains obtained form rabbits and purified by affinitive chromatography. The IgE was determined by radioimmunoassay, using the PRIST technique. If we look at all published works about normal levels of immunoglobulins in serum, we can see many differences among the results obtained by different authors. Our results are different as well; however, there is no difference in IgE levels. In our work, the secretory IgA level cannot be compared as we do not have any other study available for comparison. We think that our results differ from those obtained by other authors because of differences in laboratory and statistical techniques and other factors such as environment, constitution, nutrition, etc.