Spiders’ webs hum with information
Like strings on a guitar, spider silks can vibrate along a wide range of frequencies, transmitting information about prey, other spiders and even the condition of the web itself, researchers say.
Spiders have bad eyesight and are known to rely on the vibrations of their webs to alert them to the presence of captives. To discover more about the vibrations, British scientists fired lasers and bullets at individual spider strings and used ultra-high-speed cameras to record the results. They found that the strings vibrated across a wider range of harmonics compared with other materials, and that the type of vibration varied with the type of impact and the quality of the individual silk.
The vibrations help a spider determine what sort of prey has landed in its web, the researchers concluded. Spiders can also produce different kinds of silk depending on their needs, essentially “tuning” their webs to the environment and hunting conditions. Their study was published in the journal Advanced Materials.
“Spider silks are unique in that the spider can choose what the properties are,” said Beth Mortimer, an arachnologist at Oxford University and the lead researcher on the study. “It allows the spider to have a toolbox that can respond to different humidity conditions or to availability of different types of prey.”
New fossil offers clues on early Ichthyosaurs
Loosely resembling modern dolphins, Ichthyosaurs were distant relatives of snakes and lizards. But although numerous Ichthyosaur fossils have been found since the 19th century, paleontologists remain unsure which animal they may have evolved from.
Now, researchers say they have recovered an early Ichthyosaur fossil in southern China that fills in some evolutionary blanks. The specimen, which lived about 248 million years ago, had unusually large flippers that could have been used to walk on land. It retained other features of land-dwelling reptiles as well, including a short snout and body trunk.
The findings support the theory that Ichthyosaurs evolved from land-dwelling reptiles that returned to the ocean, said Ryosuke Motani, a paleontologist at the University of California, Davis, and the lead author of the study, which was published online by the journal Nature.
“When reptiles and mammals go marine, they typically go through a stage where they become amphibious and heavy, presumably to counter the waves near the coast,” he said. “This stage was mysteriously lacking from the fossil record of Ichthyosaurs before. Now we have this new animal to fill the gap.”
– New York Times