Visual determinants of prey chasing behavior in a mudflat crab

Abstract

The crab Neohelice inhabits mudflats where it is preyed by gulls and, conversely, preys on smaller crabs. Therefore, to the sight of moving stimuli, this crab can behave as prey or predator. The crab escape response to visual stimuli has been extensively investigated from the behavioral to the neuronal level. The predatory response (PR), however, has not yet been explored. Here, we show that this response can be reliably elicited and investigated in a laboratory arena. By using dummies of three different sizes moved on the ground at three different velocities over multiple trials, we identified important stimulation conditions that boost the occurrence of the PR and its chances of ending in successful prey capture. The PR probability was rather sustained during the first 10 trials of our experiments but then declined. The PR was elicited with high probability by the medium size dummy, less effectively by the small dummy, and hardly brought about by the large dummy, which mostly elicited avoidance responses. A GLMM analysis indicated that the dummy size and the tracking line distance were two strong determinants for eliciting the PR. The rate of successful captures, however, mainly depended on the dummy velocity. Our results suggest that crabs are capable of assessing the distance to the dummy and its absolute size. The PR characterized here, in connection with the substantial knowledge of the visual processing associated to the escape response, provides excellent opportunities for comparative analyses of the organization of two distinct visually-guided behaviors in a single animal.

Multielectrode Recordings From Identified Neurons Involved in Visually Elicited Escape Behavior

“…This study represents our first approach to using multielectrode recording in the crab. For this reason, we included in our experiments stimuli that proved to be effective both for identifying different lobula neurons (Medan et al, 2015 ; Tomsic et al, 2017 ; Scarano et al, 2018 , 2020 ) and for eliciting a variety of behavioral responses in this animal, such as escape response (Oliva and Tomsic, 2012 ; Scarano and Tomsic, 2014 ), predatory response (Gancedo et al, 2020 ) and optomotor response (Barnatan et al, 2019 ). Computer-generated visual stimuli were projected on a computer screen (Samsung S20C300L) placed at a distance of 20 cm, covering the frontolateral right side of the animal.…”

“…It is a highly visual semiterrestrial crab that inhabits densely populated mudflat environments. In nature, the crab is regularly engaged in social interactions that include burrow defense, courtship, chasing after smaller individuals and being chased by larger ones (Fathala and Maldonado, 2011 ; Sal Moyano et al, 2016 ; Tomsic et al, 2017 ; Gancedo et al, 2020 ), all activities that are guided by sight. The crab also uses vision to detect and avoid aerial predators (Magani et al, 2016 ).…”

Azimuthal invariance to looming stimuli in the Drosophila giant fiber escape circuit

“…Animals utilize or ignore the positional information of a visual stimulus when selecting behaviors ( Allen et al, 2021 ; Benucci, 2022 ; Bianco et al, 2011 ; DiCarlo et al, 2012 ; Gancedo et al, 2020 ; Peek, 2018 ; Pouget and Snyder, 2000 ; Rolls, 2012 ). If an object approaches on a direct collision course, its location can inform the selection of motor programs, including the fleeing direction of crabs and mice, postural adjustments preceding takeoff in Drosophila melanogaster and -start direction in fish ( Dunn et al, 2016 ; Hemmi and Tomsic, 2012 ; Peek, 2018 ).…”

A monocular wide-field speed sensor inspired by the crabs’ visual system for traffic analysis

“…Moving objects on the horizon line correspond to conspecifics of similar size [16]. Finally, movements below the horizon line could indicate prey to be attacked [17]. An interesting fact is that elongated eyestalks have evolved in fiddler crabs with a smaller distance between the two eyes.…”