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.
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 also can produce different kinds of silk depending on their needs, essentially “ tuning” their webs to the environment and hunting conditions.
The study was published in the journal Advanced Materials.
Catfish whiskers sense pH changes, track prey
John T. Caprio, a physiologist at Louisiana State University, was studying how chemical stimuli were encoded by a Japanese catfish’s taste system when he noticed a strong reaction from the whiskers.
Further study revealed that previously undetected sensors on the whiskers were responding not to the chemical itself but rather to the effect it was having on the water.
“It was changing the pH of the water,” he said.
The researchers then placed the catfish in aquariums with hidden polychaete worms, their preferred prey. The worms release tiny amounts of carbon dioxide and hydrogen when they breathe, raising the water’s acidity and thereby lowering its pH.
Even in the dark, the catfish were drawn to the area with the worms. The work was published in the journal Science.
— The New York Times