Yawning is a stereotyped behavior widely observed in vertebrates, serving as an adaptation to the environment. Previous research has highlighted the correlations between yawning and physiological arousal or temperature regulation. However, the majority of those studies have primarily focused on endothermic animals. Thus far, the function of yawning in ectothermic animals remains unclear. In this study, we observed the behavior of leopard geckos, Eublepharis macularius, ectothermic reptiles, over a period of 3 days under constant ambient temperatures of 25°C, 30°C, or 35°C. By investigating the relationship between temperature, spontaneous yawning, and activity levels, we found that yawning frequency is affected by ambient temperature, and also observed a significant increase in post-yawning activity particularly under the 30°C and 35°C conditions. Furthermore, a near 24-hour periodicity in yawning was detected under all temperature conditions. These results align with previous studies conducted on endothermic animals, suggesting the conservation of primitive functions of yawning across vertebrate species.

To ensure survival and reproduction, organisms must continually adapt to environmental fluctuations, such as temperature, humidity, oxygen level, and salinity. Particularly, temperature profoundly influences biochemical reactions crucial for survival. Here, we present the mechanisms employed by the nematode Caenorhabditis elegans to anticipate and respond to cold temperatures. Our findings reveal that temperature is detected by specific neurons linked to various physiological processes in the gut, spermatheca, and muscles. Notably, the gut, a primary fat storage organ in C. elegans, regulates fat mobilization and accumulation in a temperature-dependent manner, thereby contributing to temperature adaptation. Furthermore, normal spermatogenetic mechanisms influence cold tolerance by modulating the responsiveness of thermosensory neurons to temperature changes. Considering our results together with recent reports, we suggest that a polyU-specific endoribonuclease expressed in muscle cells plays a role in cold tolerance through a non-cell-autonomous mechanism, possibly involving transportation intertissues. Thus, understanding cold tolerance and temperature acclimation in C. elegans can provide valuable insights on systemic physiological regulation in response to temperature fluctuations. Moreover, they could help elucidate the actions of thermosensory neurons and their downstream neuronal circuits or neuropeptides on the peripheral organs.

The lung of marine snakes varies in structure and function related to diversity of phylogeny, behavior, and environment. All species are secondarily marine and retain dependence on aerial breathing, although some also exchange gases across the skin. Generally, there is an elongated functional right lung, and the left lung is vestigial or absent. Respiratory gases are exchanged in the ‘vascular lung’ segment, which may include the trachea, whereas the more distal ‘saccular lung’ has a poorly vascularized muscular wall, terminates blindly, and facilitates storage of oxygen. In terrestrial scansorial species of snakes, the vascularized segment of the lung is relatively short to prevent gravity-induced edema when the body is vertical or upright. In contrast, the vascular lung in marine snakes is relatively long. In the file snake Acrochordus granulatus, an exceptionally elongated vascular lung is shown to maximize oxygen storage when the snake is submerged at neutral buoyancy in shallow-water habitats. In deeper diving sea snakes, the entire lung is shorter, and the saccular segment functions to store oxygen. Movement of air within the lung is possible by means of body movements, but such behavior in naturally diving snakes is not well understood. Marine snakes avoid decompression sickness (the bends) by ‘metering’ the transfer of nitrogen from lung to seawater by varying pulmonary bypass of blood flow via intraventricular shunts and simultaneously varying blood flow to the skin. These complex cardiovascular actions are also influenced by the need of metabolizing tissues for oxygen uptake from lung stores or ambient water.

Tardigrades are small metazoans renowned for their exceptional tolerance against various harsh environments in a dehydrated state. Some species exhibited an extraordinary tolerance against high-dose irradiation even in a hydrated state. Given that natural sources of high radiation are rare, the selective pressure to obtain such a high radiotolerance during evolution remains elusive. It has been postulated that high radiation tolerances could be derived from adaptation to dehydration, because both dehydration and radiation cause similar damage on biomolecules at least partly, e.g., DNA cleavage and oxidation of various biomolecules, and dehydration is a common environmental stress that terrestrial organisms should adapt to. Although tardigrades are known for high radiotolerance, the radiotolerance records have been reported only for desiccation-tolerant tardigrade species and nothing was known about the radiotolerance in desiccation-sensitive tardigrade species. Hence, the relationship between desiccation-tolerance and radiotolerance remained unexplored. To this end, we examined the radiotolerance of the desiccation-sensitive tardigrade Grevenius myrops (formerly known as Isohypsibius myrops) in comparison to the well-characterized desiccation-tolerant tardigrade, Ramazzottius varieornatus. The median lethal dose (LD50) of G. myrops was approximately 2240 Gy. This was much lower than those reported for desiccation tolerant eutardigrades. The effects of irradiation on the lifespan and the ovipositions were more severe in G. myrops compared to those in R. varieornatus. The present study provides precise records on the radiotolerance of a desiccation-sensitive tardigrade and the current data supported the correlation between desiccation tolerance and radiotolerance at least in eutardigrades.

The present study investigates the physiological aspects of overwintering in an exposed microhabitat in the lime seed bug, Oxycarenus lavaterae. We found that the overwintering lime seed bugs do not survive freezing of their body fluids, but instead rely on supercooling (freeze avoidance). The seasonal modulation of the supercooling capacity was very limited, with the midwinter mean supercooling point reaching –15.5°C, but the individual variability was very high (– 6°C to – 22°C). Most of the other physiological parameters of overwintering lime seed bugs (utilization of energy substrates, changes in hydration, and metabolite composition [although metabolite levels were low]) were consistent with the general knowledge gathered for other freeze-avoiding insects. A significant exception was found in the amount of osmotically active water (“freezable” water), which constituted up to 95% of the lime seed bug body water. Such a proportion is unusually high, as it typically ranges from 59% to 86% in other insects and invertebrates. At present, we have no plausible explanation for this anomaly or its possible relationship to the lime seed bug's overwintering microhabitat.