Cells can sense a tough road ahead, plus promiscuous amoebas and sensitive birds of prey in this week’s news

Hard road
Cells may not be able see where they are going, but they can feel the squishiness of the path beneath them, say scientists at the University of California, Berkeley. Human fibroblast cells crawling on a lever changed the speed at which they contracted as the surface became stiffer. This behavior has been demonstrated before, but the new paper published online March 8 in PLoS ONE documents the first experiment to test stiffness independently from other variables that could affect a cell — such as deformations or changes in force as a surface stiffness. Studying this “durotaxis” works could help scientists to understand — and possibly to influence — how cells move to heal wounds in the body.  —Devin Powell

Not-so-chaste amoebas Supposedly asexual amoebas may be making a lot more whoopee than biologists had realized. One microscopic blob may look much like another, but recent work has identified at least 30 distinct amoeba-bearing twigs scattered around the tree of life. The classic examplar of cell splitting, Amoeba proteus , has not been caught in flagrante. But evaluating evidence for amoeboid sex within each of the branches suggests that the majority of amoeba lineages probably do have sex, says an international research team online March 23 in the Proceedings of the Royal Society B . Considering how difficult it is for macroscopic humans to observe microscopic sex, biologists may just have missed a lot. — Susan Milius

Sensitive birds

Birds of prey may be more sensitive to a rodent-killing compound than tests on other kinds of animals would suggest. The rodenticide diphacinone proved more than 20 times more toxic for American kestrels in oral doses than has been reported for mallards and bobwhites. Protecting birds of prey may require lower limits on such compounds those based on traditional toxicology tests of ducks and other game birds, U.S. federal researchers report online March 11 in Environmental Toxicology and Chemistry. They warn that diphacinone usage could rise as regulations tighten for other rodenticides. —Susan Milius

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