Biology subjects

Shaykevich, D. A.

Publications and source records attributed to Shaykevich, D. A..

5 recordsLinked to original sources

bioRxiv2026

Neural correlates of place learning in the cane toad, Rhinella marina

Learning locations by integrating external reference points, or place learning, is a form of navigation strongly associated with the mammalian hippocampus and its homologs in other vertebrates. In contrast, cue learning relies on individual environmental features and can occur independently of the hippocampus. Despite growing interest in amphibian spatial cognition and association of spatial functions with the medial pallium brain region, how amphibian brains support different spatial learning strategies remains unknown. We designed a four-arm maze to test place, cue, and turn-direction learning in the cane toad (Rhinella marina), and paired maze trials with visualization of brain activity through pS6 immunohistochemistry. Toads improved performance over time only in the place task but exhibited consistently faster exit times in the cue task. Place task toads displayed elevated brain activity only in the dorsal and lateral palliums. These observations demonstrate that amphibians can acquire spatial navigation strategies through distinct behavioral paradigms and reveal the diverse pallial contributions underlying vertebrate spatial cognition.

animal behavior and cognition↗

bioRxiv2024

Chronic recording of brain activity in awake toads

BackgroundAmphibians represent an important evolutionary transition from aquatic to terrestrial environments and they display a large variety of complex behaviors despite a relatively simple brain. However, their brain activity is not as well characterized as that of many other vertebrates, partially due to physiological traits that have made electrophysiology recordings difficult to perform in awake and moving animals. New methodWe implanted flexible mesh electronics in the cane toad (Rhinella marina) and performed extracellular recordings in the telencephalon of anesthetized toads and partially restrained, awake toads over multiple days. ResultsWe recorded brain activity over five consecutive days in awake toads and over a 15 week period in a toad that was anesthetized during recordings. We were able to perform spike sorting and identified single- and multi-unit activity in all toads. Comparison with existing methodsTo our knowledge, this is the first report of a modern method to perform electrophysiology in non-paralyzed toads over multiple days, though there are historical references to short term recordings in the past. ConclusionsImplementing flexible mesh electronics in amphibian species will allow for advanced studies of the neural basis of amphibian behaviors.

neuroscience↗

bioRxiv2024

Neural and sensory basis of homing behavior in the invasive cane toad, Rhinella marina

The behavioral, sensory, and neural bases of vertebrate navigation are primarily described in mammals and birds. While many studies have explored amphibian navigation, none have characterized brain activity associated with navigation in the wild. To address this knowledge gap, we conducted a study on navigation in the cane toad, Rhinella marina. First, we performed a translocation experiment to describe how invasive cane toads in Hawaii navigate home and observed homing following displacements of up to one kilometer. Next, we tested the effect of olfactory and magnetosensory manipulations on homing, as these senses are most commonly associated with amphibian navigation. We found that neither ablation alone prevents homing, further supporting that toad navigation is multimodal. Finally, we tested the hypothesis that the medial pallium, the amphibian homolog to the hippocampus, is involved in homing. Our comparisons of neural activity revealed evidence supporting a conservation of neural structures associated with navigation across vertebrates consistent with neural models of amphibian spatial cognition from recent laboratory studies. Our work furthers our evolutionary understanding of spatial behavior and cognition in vertebrates and lays a foundation for studying the behavioral, sensory, and neural bases of navigation in an invasive amphibian.

animal behavior and cognition↗

bioRxiv2022

Contrasting parental roles shape sex differences in poison frog space use but not navigational performance

Sex differences in vertebrate spatial abilities are typically interpreted under the adaptive specialization hypothesis, which posits that male reproductive success is linked to larger home ranges and better navigational skills. The androgen spillover hypothesis counters that enhanced male spatial performance may be a byproduct of higher androgen levels. Animal groups that include species where females are expected to outperform males based on life-history traits are key for disentangling these hypotheses. We investigated the association between sex differences in reproductive strategies, spatial behavior, and androgen levels in three species of poison frogs. We tracked individuals in natural environments to show that contrasting parental sex roles shape sex differences in space use, where the sex performing parental duties shows wider-ranging movements. We then translocated frogs from their home areas to test their navigational performance and found that the caring sex outperformed the non-caring sex only in one out of three species. In addition, males across species displayed more explorative behavior than females. Furthermore, androgen levels correlated with explorative behavior and homing accuracy. Our findings suggest that poison frog reproductive strategies shape space use patterns but not navigational performance, providing counterevidence to the prevailing view of adaptive sex differences in spatial abilities.

animal behavior and cognition↗

bioRxiv2021

Long distance homing in the cane toad (Rhinella marina) in its native range

Many animals exhibit complex navigation over different scales and environments. Navigation studies in amphibians have largely focused on species with life histories that require advanced spatial capacities, such as territorial poison frogs and migratory pond-breeding amphibians that show fidelity to mating sites. However, other species have remained relatively understudied, leaving the possibility that well-developed navigational abilities are widespread. Here, we measured short-term space use in non-territorial, non-migratory cane toads (Rhinella marina) in their native range in French Guiana. After establishing home range, we tested their ability to return to home following translocations of 500 and 1000 meters. Toads were able to travel in straight trajectories back to home areas, suggesting map-like navigational abilities similar to those observed in amphibians with more complex spatial behavior. These observations break with the current paradigm of amphibian navigation and suggest that navigational abilities may be widely shared among amphibians.

animal behavior and cognition↗