A membrane is born: origin of the autophagosomal compartment

Autophagy is one of the major catabolic processes present in eukaryotic cells, conserved through evolution, by which damaged or superfluous organelles are degraded in response to different stimuli. A hallmark of the autophagic pathway is the formation of double or multiple layered membranes that engulf the material to be finally degraded in the lysosomes. Despite enormous advances in the last few years to understand the autophagic process at the molecular level, the origin of the sequestering membrane has remained elusive for more than forty years and it is still a matter of debate. In this review we have summarized recent experimental evidence indicating that more than one membrane source may exist. Even though de novo formation or assembly of the isolation membrane has been proposed, recent data points to the participation of specific organelles in the biogenesis of the sequestering membrane.     

Natural born killers: an invasive amphipod is predatory throughout its life-history

Introduced predators can have profound impacts on prey populations, with subsequent ramifications throughout entire ecosystems. However, studies of predator–prey interaction strengths in community and food-web analyses focus on adults or use average body sizes. This ignores ontogenetic changes, or lack thereof, in predatory capabilities over the life-histories of predators. Additionally, large individual predators might not be physically capable of consuming very small prey individuals. Both situations are important to resolve, as native prey may or may not therefore experience ontogenetic or size refuges from invasive predators. Here, we find that the freshwater amphipod invader, Gammarus pulex, is predatory throughout its development from juvenile through to adult. All size classes collected in the field had a common prey, nymphs of the mayfly Baetis rhodani, in their guts. In an experiment with predator, prey and experimental arenas scaled for body size, G. pulex juveniles and adults consumed B. rhodani in all size-matched categories. In a second experiment, the largest G. pulex individuals were able to prey on the smallest B. rhodani. Thus, the prey do not benefit from any ontogenetic or size refuge from the predator. This corroborates with the known negative population abundance relationships between this invasive predator and its native prey species. Understanding and predicting invasive predator impacts will be best served when interactions among all life-history stages of predator and prey are considered.