Jakob, E. | Search bioRxiv

bioRxiv2025

Biological point-light displays scanning by the principal eyes of a jumping spider

The semi-rigid structure of bodies forces mobile animals to move in rhythmic patterns shared by all creatures with skeletons, exoskeletons, or limb connections. This pattern, known as biological motion, is instantly recognizable and conveys "animacy," even when body shape is removed and only a cloud of moving dots is shown. Indeed, motion alone is so informative that some animals can infer the original shape based on the dots concurrent activity. Jumping spiders, highly visual arthropods, divide motion detection and shape recognition between their four pairs of eyes. Previous studies found that they can distinguish biological from non-biological motion using only their motion-detecting anterior lateral eyes yet seemed unable to extract shape from motion. In this study, we examined how the anterior medial eyes of jumping spiders--which are used for shape recognition--respond to dot clouds depicting biological or non-biological motion. Using a custom eye tracker, we monitored retinal movements during presentation of static and moving stimuli. We found spiders change their retinal shifting pattern based on both the targets motion (biological or not) and implied structure (i.e., whether dots suggest a coherent shape). These results reveal that jumping spiders analyze motion with more complexity than previously thought, suggesting a deeper integration of motion and form processing within their minuscule, modular brains.

animal behavior and cognition↗

bioRxiv2022

Deconstructing a visual signal: the role of motion and colour in predator deterrence

Visual animal communication, whether to the same species or to other species, is largely conducted through dynamic and colourful signals. For a signal to be effective, the signaller must capture and retain the attention of the receiver. Signal efficacy is also dependent on the sensory limitations of the receiver. However, most signalling studies consider movement and colour separately, resulting in a partial understanding of the signal in question. We explored the structure and function of predator-prey signalling in the jumping spider-tephritid fly system, where the prey performs a wing waving display that deters an attack from the predator. Using a custom-built spider retinal tracker combined with visual modelling, and behavioural assays, we studied the effect of fly wing movement and colour on the jumping spiders visual system. We show that jumping spiders track their prey less effectively during wing display and this can be attributed to a series of fluctuations in chromatic and achromatic contrasts arising from the wing movements. These results suggest that displaying flies deter spider attacks by manipulating the movement biases of the spiders visual system. Our results emphasise the importance of receiver attention on the evolution of interspecific communication.

animal behavior and cognition↗