Jumping Spiders Can Distinguish Living from Non-Living Things Through Vision Cues Used by Humans, Vertebrates

A new study recently showed jumping spiders could distinguish living from non-living things in their marginal vision through the use of the same cues humans and other vertebrates are using.

A Phys.org report specified that the ability to detect other living objects in the surroundings "is a key skill for any animal." It is crucial for searching for mates, avoiding predators, not to mention catching prey.

Essentially, both the vertebrate's and invertebrates' movements are distinct from inanimate objects as their rigid bones and exoskeletons limit the relative positioning of specific parts of the body.

Most vertebrates can recognize this movement's biological pattern from very limited visual information, like a point-light display, which displays dots representing the main joints' positions.

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Peripheral Vision

To examine such a phenomenon in invertebrates, for the first time, study authors partly restrained 60 wild-caught jumping spiders or Menemerus semilimbatus in scientific terms, on a spherical treadmill, and utilized a computer screen to present point-light displays on every side of their peripheral vision, only noticeable to their eyes.

In their study, Perception of biological motion by jumping spiders, published in PLOS Biology, the researchers discovered that jumping spiders, in particular, were more possible to try to turn and face displays that exhibited random movements, compared to those that moved in a more biological manner, with the distances between joints guarded.

Such a result appears opposite the expectation that spiders need to focus their attention on things in their surroundings that appear to have life, like potential prey, predator, or mate.

Nevertheless, the authors suggested that such behavior may enable, specifically, the jumping spiders to focus their forward-facing primary eyes on unidentifiable objects to get a better look.

Essentially, the complex vision evolved independently through the use of the relative positioning of the joints, which has most possibly arisen convergently in the two groups of animals.

Secondary Eyes, a 'Marvelous Tool'

Describing their study finding, a similar Science Daily report said, the study investigators said, the secondary eyes a "marvelous tool." In this experiment, they observed how they alone could differentiate or tell apart living things from non-living objects by using the semi-rigid pattern of motion that characterizes the formers and minus the support of any shape cue.

Searching for the presence of such a skill, formerly identified only in vertebrates, now opens up new and exciting viewpoints on the evolution of visual perception.

The authors said they could not wait to see what other visual hints can be perceived and understood by these tiny animals.

Jumping Spiders

Among the jumping spider species, according to the Washington State University's Department of Entomology, Phidippus audax is one of the most common, not to mention, among the most conspicuous type. It is frequently called Orchard spiders.

This type of jumping spider is black with a unique irregular orange to white spot on the back of its abdomen. It can be found around homes and in gardens.

Essentially, jumping spiders are part of the Salticidae family. Salticid spiders come in different sizes and color patterns. Hunters only during the day have good eyesight, depending primarily on movement to find prey.

They follow their prey before attacking in a speedy leap. Jumping spiders are putting out a line of webbing when they are jumping and can at times be seen dangling from this silken dragline following a failed leap.

Related information is shown on BBC News's YouTube video below: