Inner Workings: Inside the mind of a jumping spider.

At first, there were explosions. Neurobiologists investigating the peculiar behavior of the jumping spider sought to record its neurons. But the scientists’method always spelled doom for the creatures: peeling back the spiders’ exoskeleton to expose the brain caused vital fluids to burst forth. For decades, neurobiologists and ecologists have struggled to understand just how the poppy seed-sized brains of jumping spiders gave rise to one of the richest behavioral repertoires among arachnids. But a research team recently discovered a minimally invasive way, using superstrong electrodes, to reach the spider brain without major surgery (1). The technical breakthrough has opened a new frontier of neurophysiology, allowing scientists to record brain activity while spiders detect, track, and decide how to respond to their prey and potential mates. Members of the jumping spider family (called Salticidae) stand out among spiders for their sharp vision. Four pairs of eyes form a turret around the animal’s head that provides a near-360° world view. The two largest eyes, placed front and center, detect color and fine details, and the remaining eyes serve as low-resolution motion detectors that help orient the animal to objects of interest. Unlike web-spinning spiders that wait for food to land in their webs, jumping spiders use their specialized visual system to actively stalk and pounce on their prey. The hairy arachnids often scuttle along circuitous routes to avoid detection, tackling their target from above. Female jumping spiders also size up the gyrations and gesticulations of males performing courtship dances. “There are a lot of hypotheses about how jumping spiders are able to do these complex things,” says Damian Elias, who studies jumping spiders at the University of California, Berkeley. Finally being able to record from the spiders’ neurons will be a game-changer, he says. “It’s actually going to let us test those hypotheses about their cognitive abilities.”