Predatory behavior under monocular and binocular conditions in the semiterrestrial crab Neohelice granulata

Thomas Harper; Sergio Iván Nemirovsky; Daniel Tomsic; Julieta Sztarker

doi:10.3389/fnbeh.2023.1186518

Predatory behavior under monocular and binocular conditions in the semiterrestrial crab Neohelice granulata

Front Behav Neurosci. 2023 May 25:17:1186518. doi: 10.3389/fnbeh.2023.1186518. eCollection 2023.

Authors

Thomas Harper¹, Sergio Iván Nemirovsky², Daniel Tomsic^{1

3}, Julieta Sztarker^{1

3}

Affiliations

¹ Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina.
² Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN), CONICET, Universidad de Buenos Aires, Buenos Aires, Argentina.
³ Departamento de Fisiología, Biología Molecular y Celular "Dr. Héctor Maldonado", Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.

Abstract

Introduction: Neohelice granulata crabs live in mudflats where they prey upon smaller crabs. Predatory behavior can be elicited in the laboratory by a dummy moving at ground level in an artificial arena. Previous research found that crabs do not use apparent dummy size nor its retinal speed as a criterion to initiate attacks, relying instead on actual size and distance to the target. To estimate the distance to an object on the ground, Neohelice could rely on angular declination below the horizon or, since they are broad-fronted with eye stalks far apart, on stereopsis. Unlike other animals, binocular vision does not widen the visual field of crabs since they already cover 360° monocularly. There exist nonetheless areas of the eye with increased resolution.

Methods: We tested how predatory responses towards the dummy changed when animals' vision was monocular (one eye occluded by opaque black paint) compared to binocular.

Results: Even though monocular crabs could still perform predatory behaviors, we found a steep reduction in the number of attacks. Predatory performance defined by the probability of completing the attacks and the success rate (the probability of making contact with the dummy once the attack was initiated) was impaired too. Monocular crabs tended to use frontal, ballistic jumps (lunge behavior) less, and the accuracy of those attacks was reduced. Monocular crabs used prey interception (moving toward the dummy while it approached the crab) more frequently, favoring attacks when the dummy was ipsilateral to the viewing eye. Instead, binocular crabs' responses were balanced in the right and left hemifields. Both groups mainly approached the dummy using the lateral field of view, securing speed of response.

Conclusion: Although two eyes are not strictly necessary for eliciting predatory responses, binocularity is associated with more frequent and precise attacks.

Keywords: binocular integration; crustacean; eye occlusion; predatory strategy; stereopsis.

Grants and funding

This work was supported by the following grants to JS: PICT 2020-00867 and DT: PICT 2019–00724 from the Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT) and Grant PIP 2021-2023. GI: 11220200101248CO from CONICET. This research has received funding from the European Union’s Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie Grant Agreement Nos. 691154, STEP2DYNA and Grant Agreement No. 778062, ULTRACEPT.