Biology subjects

Otsuka, R.

Publications and source records attributed to Otsuka, R..

4 recordsLinked to original sources

bioRxiv2026

Tourism impacts on fecal glucocorticoid metabolites of free-ranging mountain gorillas in Bwindi Impenetrable National Park, Uganda

Mountain gorilla tourism plays a vital role in their conservation; however, increasing tourism intensity may elevate gorilla stress levels. Despite this concern, knowledge regarding its physiological effects remains limited. This study non-invasively assessed the impact of tourism on gorilla stress by measuring fecal glucocorticoid metabolites (fGCMs). Fecal samples were collected from habituated gorilla groups in Bwindi Impenetrable National Park, Uganda, between 2017-2018. Concentrations of fGCMs were analyzed using a field-friendly extraction method and enzyme immunoassay. To assess the specific impacts of tourism, we focused on the Rushegura group, which is frequently visited by tourists, and used Bayesian linear mixed-effects models to examine associations between log-transformed fGCMs (log-fGCMs) and tourism intensity (daily tourist numbers and visit frequency). Additionally, we performed a inter-group comparison with the Mubare group, which was visited less frequently but underwent more dynamic social changes, to evaluate how log-fGCMs levels differed across different group contexts. In the Rushegura group, the number of tourists and visits frequently exceeded the maximum limits established by the tourism guidelines (i.e., one visit of eight people per day). In this group, log-fGCMs increased with the number of tourists and were higher during days with multiple visits. The model incorporating visit frequency demonstrated better predictive performance. On the other hand, Mubare gorillas showed higher log-fGCMs than Rushegura gorillas, likely reflecting the influence of social instability. These findings underscore the importance of adhering to the tourism guidelines--specifically regarding group size and visit frequency--to minimize physiological stress and associated risks, such as disease transmission. Although this pilot study lacks site-specific biological validation for this subspecies, the results provide preliminary insights into the physiological stress responses of Bwindi mountain gorillas to tourism. Further long-term, large-scale studies involving multiple gorilla groups are necessary to better understand how tourism and other factors (e.g., habituation status and social factors) influence their stress levels.

ecology↗

bioRxiv2024

Tools of Hibernation Measurement and Interpretation (TOHMIN) for quantifying various values from body temperature fluctuation during hibernation

Hibernation is a fascinating physiological phenomenon that dramatically reduces basal metabolism and thermogenesis, resulting in a large deviation in body temperature (Tb) from homeothermic ranges in mammals. Although high-resolution long-term Tb recording in wild or laboratory animals has become possible through data loggers, few standardized methods to analyze details of hibernation patterns are available, making it difficult to reproduce and compare the results across different studies and species. To facilitate the analysis of hibernation patterns and accelerate hibernation research, we developed an open-source program, tools of hibernation measurement and interpretation (TOHMIN). As a proof of concept, we analyzed a dataset from two pilot studies on (1) the effects of distinct diets on hibernation patterns and (2) differences in hibernation patterns between males and females in a mammalian hibernator, Syrian hamster (Mesocricetus auratus), and found previously undetectable fine-scale differences in hibernation patterns. First, different types of diets affected the duration of periodic arousal. Second, females maintained higher body temperatures during periodic arousal than males. Third, the duration of the pre-hibernation period was negatively correlated with the hibernation period for this species. Thus, TOHMIN accelerates studies to assess the effects of various experimental manipulations on hibernation phenotypes in mammals.

physiology↗

bioRxiv2023

What makes the effect of protein mutations difficult to predict?

Protein engineering increasingly relies on machine learning models to computationally pre-screen promising novel candidates. Although machine learning approaches have proven effective, their performance on prospective screening data leaves room for improvement; prediction accuracy can vary greatly from one protein variant to the next. So far, it is unclear what characterizes variants that are associated with large prediction error. In order to establish whether structural characteristics influence predictability, we created a combinatorial variant dataset for an enzyme, that can be partitioned into subsets of variants with mutations at positions exclusively belonging to a particular structural class. By training four different variant effect prediction (VEP) models on structurally partitioned subsets of our data, we found that predictability strongly depended on all four structural characteristics we tested; buriedness, number of contact residues, proximity to the active site and presence of secondary structure elements. These same dependencies were found in various single mutation enzyme variant datasets, with effect directions being specific to the assay. Most importantly, we found that these dependencies are highly alike for all four models we tested, indicating that there are specific structure and function determinants that are insufficiently accounted for by popular existing approaches. Overall, our findings suggest that significant improvements can be made to VEP models by exploring new inductive biases and by leveraging different data modalities of protein variants, and that stratified dataset design can highlight areas of improvement for machine learning guided protein engineering.

bioinformatics↗

bioRxiv2021

What is unique about the human eye? Comparative image analysis on the external eye morphology of human and nonhuman great apes

The gaze-signaling hypothesis and the related cooperative-eye hypothesis posit that humans have evolved special external eye morphology, including exposed white sclera (the white of the eye), to enhance the visibility of eye-gaze direction and thereby facilitate conspecific communication through joint-attentional interaction and ostensive communication. However, recent quantitative studies questioned these hypotheses based on new findings that humans are not necessarily unique in certain eye features compared to other great ape species. Therefore, there is currently a heated debate on whether external eye features of humans are distinguished from those of other apes and how such distinguished features contribute to the visibility of eye-gaze direction. This study leveraged updated image analysis techniques to test the uniqueness of human eye features in facial images of great apes. Although many eye features were similar between humans and other species, a key difference was that humans have uniformly white sclera which creates clear visibility of both eye outline and iris -the two essential features contributing to the visibility of eye-gaze direction. We then tested the robustness of the visibility of these features against visual noises such as darkening and distancing and found that both eye features remain detectable in the human eye, while eye outline becomes barely detectable in other species under these visually challenging conditions. Overall, we identified that humans have distinguished external eye morphology among other great apes, which ensures robustness of eye-gaze signal against various visual conditions. Our results support and also critically update the central premises of the gaze-signaling hypothesis.

animal behavior and cognition↗