Spider likes smelly socks, plus more in this week's news

EARLY SEA An ancient sea species about 4 centimeters high, fossilized in China’s Lantian black shale, appears to have a holdfast for sticking to sediment, a stalk, and a crown of tentacle-like structures. Zhe Chen
CTYPE html PUBLIC “-//W3C//DTD HTML 4.0 Transitional//EN” “”> When life got complicated What look like fossilized seaweeds plus other whatzits from the Lantian rock formation in southern China suggest that life may have started getting fancy earlier than researchers had thought. Before a new analysis, paleontologists often cited fossil sea species from what’s called the Avalon biota, dating back 579 million to 565 million years, as the earliest known array of complex, multicellular life forms. Lantian fossils, however, take five general forms and date from between about 580 million and 635 million years ago, Xunlai Yuan of the Nanjing Institute of Geology and Paleontology in China and his colleagues report in the Feb. 17 Nature . — Susan Milius Spider likes smell of dirty socks A spider that doesn’t prey on people responds, apparently favorably, to human scent in the form of the perfume of a recently worn sock, report researchers in Kenya and New Zealand. The East African jumping spider Evarcha culicivora has the unusual, vampire-by-proxy feeding habit of hunting blood-carrying mosquitoes. Spiders particularly favor Anopheles gambiae , notorious spreaders of malaria, which themselves respond to human odors. Thus a whiff of humanity might guide the spiders to a mosquito dinner. In a test, the spiders lingered longer in air flows wafting from a smelly sock than in air from a clean one, the researchers report online February 16 in Biology Letters . — Susan Milius Ants decide rationally together
Collective decisions made by ant colonies can be rational even when individual colony members would not be. When offered a tricky choice between possible nest sites, Temnothorax rugatulus colonies showed roughly the same preference regardless of whether researchers added a decoy. That decoy, a third option clearly inferior to one of the other choices, typically skews human preferences for the original two options, even though the originals don’t change. Ants alone, but not collectively, fell into the same trap, Takao Sasaki and Stephen Pratt of Arizona State University in Tempe report in an upcoming Behavioral Ecology. —Susan Milius
Flocking is driving me crazy Ravens roosting and feeding in big, loose flocks surprised an international team of researchers by showing higher concentrations of a stress hormone than did raven pairs in the same forest doing the presumably demanding task of defending their own territories. In the off-season for breeding, even males maintaining a territory didn’t have corticosterone concentrations as high as their free-styling, flock-living neighbors in Poland’s Białowieża forest. Such findings could inspire more research on links between hormones and the evolutionary pressures on gregarious or territorial life among long-lived species, an international team of researchers reports in an upcoming Biology Letters . — Susan Milius Bats make friends They probably don’t poke each other to say hello, but bats form social networks and will roost with old friends, finds a new analysis of colonies of Bechstein’s bats. In loose groups where members come and go, the capacity to maintain long-term social relationships has been found in just a few high-functioning animals such as primates, dolphins and elephants. The discovery that bats form bonds that aren’t tightly driven by blood relationships suggests that social complexity isn’t as exclusive as presumed, German and Swiss researchers report February 8 in the Proceedings of the Royal Society B . — Rachel Ehrenberg

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