Responses of infrared-sensitive tectal units of the pit viper Crotalus atrox to moving objects

A perspective on neuroethology: what the past teaches us about the future of neuroethology

For 100 years, the Journal of Comparative Physiology-A has significantly supported research in the field of neuroethology. The celebration of the journal's centennial is a great time point to appreciate the recent progress in neuroethology and to discuss possible avenues of the field. Animal behavior is the main source of inspiration for neuroethologists. This is illustrated by the huge diversity of investigated behaviors and species. To explain behavior at a mechanistic level, neuroethologists combine neuroscientific approaches with sophisticated behavioral analysis. The rapid technological progress in neuroscience makes neuroethology a highly dynamic and exciting field of research. To summarize the recent scientific progress in neuroethology, I went through all abstracts of the last six International Congresses for Neuroethology (ICNs 2010-2022) and categorized them based on the sensory modalities, experimental model species, and research topics. This highlights the diversity of neuroethology and gives us a perspective on the field's scientific future. At the end, I highlight three research topics that may, among others, influence the future of neuroethology. I hope that sharing my roots may inspire other scientists to follow neuroethological approaches.

Pit viper thermography: the pit organ used by crotaline snakes to detect thermal contrast has poor spatial resolution

Pit vipers detect infrared radiation by means of temperature contrasts created on their pit organ membranes. Signals from pit organs integrate with visual signals in the optic tectum, leading to the conjecture that the facial pits operate as an extension of the visual system. Because similar mechanisms underlie thermal imaging technology, imagery from thermal cameras is often used to infer how pit vipers perceive their environment. However, pit organs lack a focusing mechanism, and biophysical models predict that pit organs should have poor spatial resolution compared with thermal imaging cameras. Nevertheless, behavioral studies occasionally suggest pits may have better resolution than predicted by biophysical models, indicating that processing in the central nervous system may improve imaging. To estimate the spatial resolution of the neural image informing behavior, we recorded snake responses evoked by targets moving across backgrounds composed of two contrasting temperatures with an average temperature equal to the target temperature. An unresolved background would appear uniform; thus, the target would be detectable only if the background pattern were resolved. Western rattlesnakes (Crotalus oreganus) displayed no statistically significant responses to targets presented in front of patterned backgrounds, regardless of the temperature contrasts or spatial frequencies within the background, but responded strongly to targets presented in front of homogeneous backgrounds. We found no evidence that the pit organ system can resolve spatial details subtending an angle of 9 deg or less. We discuss the implications of these results for understanding pit organ function in ecologically relevant habitats with thermal heterogeneity.

Multiple Routes of Light Signaling during Root Photomorphogenesis

Plants dynamically adjust their architecture to optimize growth and performance under fluctuating light environments, a process termed photomorphogenesis. A variety of photomorphogenic responses have been studied extensively in the shoots, where diverse photoreceptors and signaling molecules have been functionally characterized. Notably, accumulating evidence demonstrates that the underground roots also undergo photomorphogenesis, raising the question of how roots perceive and respond to aboveground light. Recent findings indicate that root photomorphogenesis is mediated by multiple signaling routes, including shoot-to-root transmission of mobile signaling molecules, direct sensing of light by the roots, and light channeling through the plant body. In this review we discuss recent advances in how light signals are transmitted to the roots to trigger photomorphogenic responses.