Jumping spiders, or Salticidae, aside from being seriously creepy, make use of a unique vision system which lets them stalk and hunt their prey before springing into action.
A Salticid uses visual information garnered from four pairs of eyes, each of which has a specialized function. Their specialized eyes provide them with a nearly 360 degree view of their surroundings and give them a spatial resolution more acute than all insects and most mammals.
Considering the average jumping spider has a brain about the size of a poppy seed, it's an amazing ability that's given them an evolutionary advantage and made them the focus of a large number of neurophysiological studies.
But studying their visual system in a thorough way has been next to impossible. The tiny bodies of Salticidae have an enormous internal pressure, and if the cuticle which protects their internal structure is ruptured, it kills them instantly.
To solve the problem of handling the spiders to study their visual quirks without killing them, neurobiologists at the Cornell University Hoy Lab have built a 3D printed harness to hold them securely while they're being studied without damaging their delicately balanced internal pressure.
Until now, only a precious few recordings of the jumping spider's eyes at work have had to suffice in efforts to understand how the arachnids see with such acuity. But using the harness, the researchers at Cornell say they've been able to create detailed neurophysiological recordings from the brains of the Phidippus audax (a common North American jumping spider) which demonstrates the nonlinear interactions between the spider's principal and secondary sets of eyes.
A postdoctoral student in at the Hoy Lab, Gil Menda, designed and built the device. Menda, Paul Shamble, Eyal Nitzany, James Golden, and Ronald Hoy are now using the 3D printed harness and a drop of wax to immobilize the study objects, and by inserting a tiny electrode into the brain of the spiders, they can record the necessary information. Menda's solution also involves a method of sealing the resulting hole in the spider's head without disrupting the subject's internal pressure. The glass-insulated tungsten electrode reaches into the spider's brain and doesn't result in the catastrophic fluid loss that has limited recording efforts in the past.
The researchers say the recordings they've made are "remarkably stable, often lasting several hours, and were made from 53 sites across 33 animals."
By employing a range of different stimuli to test the neural reactions of the spiders, the team is hoping to understand the Salticid's predatory reactions to moving targets, responses to ecologically relevant objects and the relationships between the different sets of eyes.