Biology subjects

Yagi, M.

Publications and source records attributed to Yagi, M..

5 recordsLinked to original sources

bioRxiv2023

Metabolic responses to food and temperature in deep-sea isopods, Bathynomus doederleini

Metabolic rate, the energy required per unit of time for an organism to sustain life, is influenced by both intrinsic and extrinsic factors. Despite the similarities among living organisms across the various domains of life, it has been observed that those adapted to deep-sea environments exhibit notable distinctions from those in shallower waters, even when accounting for size and temperature. However, as deep-sea organisms are infrequently kept in captivity for prolonged periods, investigations into their potential metabolic responses to food and temperature have yet to be conducted. In this study, we demonstrate the impact of food (specific dynamic action: SDA) and temperature (Q10) on the metabolic rate of the deep-sea isopod Bathynomus doederleini. Positive correlations were found between SDA parameters (peak, time to peak, duration, and factorial scope) and meal size in deep-sea organisms. The postprandial metabolic rate, at a meal size of 45.4%, increased by approximately 6.5-fold, and the duration was 20 days. Within the temperature range of their natural habitat, the overall Q10 was 2.36, indicating that a 10 {degrees}C increase would lead to a 2.4-fold increase in resting metabolic rate. The mean metabolic rate of this species, corrected for the equivalent temperature, was significantly 63% lower than the metabolic scaling rule for aquatic invertebrates. This low metabolic rate suggests that deep-sea isopods can survive for a year on a mere few grams of whale blubber at a water temperature of 10.5 {degrees}C. This information is crucial for understanding the metabolic strategies and consequences of adaptation to a deep-sea environment.

ecology↗

bioRxiv2022

The Dynorphin/Kappa Opioid Receptor mediates adverse immunological and behavioral outcomes induced by repetitive blast trauma in male mice

BackgroundAdverse pathophysiological and behavioral outcomes related to mild traumatic brain injury (mTBI), posttraumatic stress disorder (PTSD), and chronic pain are common following blast exposure and contribute to decreased quality of life, but underlying mechanisms and prophylactic/treatment options remain limited. The dynorphin/kappa opioid receptor (KOR) system helps regulate behavioral and inflammatory responses to stress and injury; however, it has yet to be investigated as a potential mechanism in either humans or animals exposed to blast. We hypothesized that blast-induced KOR activation mediates adverse outcomes related to inflammation and affective behavioral response. MethodsC57Bl/6 adult male mice were singly or repeatedly exposed to either sham (anesthesia only) or blast delivered by a pneumatic shock tube. The selective KOR antagonist norBNI or vehicle (saline) was administered 72 hours prior to repetitive blast or sham exposure. Serum and brain were collected 10 minutes or 4 hours post-exposure for dynorphin A-like immunoreactivity and cytokine measurements, respectively. At one-month post-exposure, mice were tested in a series of behavioral assays related to adverse outcomes reported by humans with blast trauma. ResultsRepetitive but not single blast exposure resulted in increased brain dynorphin A-like immunoreactivity. norBNI pretreatment blocked or significantly reduced blast-induced increase in serum and brain cytokines, including IL-6, at 4 hours post exposure and aversive/anxiety-like behavioral dysfunction at one month post exposure. ConclusionsOur findings demonstrate a previously unreported role for the dynorphin/KOR system as a mediator of biochemical and behavioral dysfunction following repetitive blast exposure and highlight this system as a potential prophylactic/therapeutic treatment target.

neuroscience↗

bioRxiv2022

Microplastic pollution in aquatic environments may facilitate misfeeding by fish

Numerous recent studies have documented ingestion of microplastics (MPs) by many aquatic animals, yet an explanation for misfeeding by fish remains unexplained. Here we tested the hypothesis that biofilm (biofouling) on MP surfaces due to exposure in the aquatic environment facilitates misfeeding in fish. Spherical polystyrene (PS) was cultured for 0 to 22 weeks in a freshwater environment to grow biofilm on the MP. Goldfish were employed in a simple feeding experiment with and without provision of genuine food at ecologically relevant MP concentrations. The absorbance (ABS), which is a proxy for biofilm formation increased exponentially within three weeks of initiation and reached a plateau after approximately five weeks. Although fish did not swallow the MPs, "capture" occurred when food pellets were in the vicinity and significantly increased in probability with exposure time. Duration of capture also increased significantly with increasing exposure. These results suggest that the drift of MPs in aquatic environments may facilitate fish misidentification of MPs as edible prey.

ecology↗

bioRxiv2021

Microplastic pollution of commercial fishes from coastal and offshore waters, Japan

Microplastics (MPs) pollution is a worldwide issue in the marine environment. There is growing concern of consuming MPs through fish, yet the current contamination status of fish collected from the deep sea surrounding Japan remains limited. We present baseline data on MPs in commercially important fishes from the coastal and offshore waters near Kyushu, Japan (East China Sea). We examined the MPs in the digestive tracts of two pelagic (n = 150 in total) and five demersal species (n = 235 in total). The fish were caught by pole and line, and bottom trawl at different geographical positions. The MPs in pelagic fish (39.1 %) were higher than demersal fish (10.3 %) and of larger sizes. The MPs correlated with habitat depth and type. There was species variation in the shape and polymer composition of MPs. These results increase our understanding of the heterogeneous uptake of MPs by fishes.

ecology↗

bioRxiv2021

Spatiotemporal variations of surface water microplastics near Kyushu, Japan: A quali-quantitative analysis

Microplastics in the ocean are threatening marine ecosystems. Although plastic contaminants are ubiquitous from rivers to polar oceans, their distribution is thought to be heterogeneous, implying that both spatial and temporal variability exist. Here, we elucidate the significant spatial and temporal (seasonal) variations in the quanti-qualitative characteristics of microplastics off the west coast of Kyushu, Japan in the East China Sea. Six surveys across nine stations (n = 54) were conducted over a 14-month period, and a total of 6131 plastic items were identified. The average microplastic abundance (items {middle dot}m-3) and size (mm) {+/-} S.D. were 0.49 {+/-} 0.92 (n = 54), and 1.71 {+/-} 0.93 (n = 6131), respectively. Differences between the highest and lowest abundances were 50-fold among monthly means (1.97 {+/-} 1.49, n = 9; 0.04 {+/-} 0.03, n = 9), and 550-fold across all net tows (5.50; 0.01). With respect to colour, polymer type, and shape, white and transparent (68.5%), polyethylene (80%) fragments (76.0%) were the dominant composition. There were statistically significant differences for each of the analytical microplastic parameters among survey months (p < 0.02). Our results provide baseline data, and lead to a more comprehensive understanding of the spatiotemporal characteristics of microplastic pollution. HighlightsO_LISignificant spatiotemporal variability in microplastic litter was detected based on the quali-quantitative analyses. C_LIO_LIAverage ({+/-} S.D.) microplastic abundance was 0.49 {+/-} 0.92 (items {middle dot}m-3) and size was 1.71 {+/-} 0.93 (mm). C_LIO_LIDifferences between highest and lowest abundances were 50-fold among monthly means, and 550-fold across all net tows. C_LIO_LIWhite and transparent polyethylene fragments were the dominant composition. C_LI

ecology↗