Biology subjects

Kawabata, Y.

Publications and source records attributed to Kawabata, Y..

3 recordsLinked to original sources

bioRxiv2017

A miniaturized threshold-triggered acceleration data-logger for recording burst movements of aquatic animals

Animal-borne accelerometers are effective tools for quantifying the kinematics of animal behaviors, such as swimming, running, and flying, under natural conditions. However, quantifying burst movements of small and agile aquatic animals (e.g., small teleost fish), such as during predatory behavior, or while fleeing, remains challenging. To capture the details of burst movements, accelerometers need to sample at a very high frequency, which will inevitably shorten the duration of the recording or increase the size of the device. To overcome this problem, we developed a high-frequency acceleration data-logger that can be triggered by a manually-defined acceleration threshold, thus allowing the selective measurement of animal burst movements. We conducted experiments under laboratory and field conditions to examine the performance of the logger. The laboratory experiment using red seabream (Pagrus major) showed that the new logger could measure the kinematics of their escape behaviors (i.e., body beat cycles and maximum acceleration values). The field experiment using free-swimming yellowtail kingfish (Seriola lalandi) showed that the loggers trigger correctly (i.e., of the 18 burst movements, 17 were recorded by the loggers). We suggest that this new logger can be applied to measure the burst movements of various small and agile animals, whose movements may be otherwise difficult to measure.

animal behavior and cognition↗

bioRxiv2017

Stepwise approach to oocyte depletion in Sry mutated XY female mice

Little is known regarding the mechanisms underlying infertility in male-to-female sex-reversed females. To gain a better understanding of germ cell dysfunction in this condition, we produced XYsry--females via the CRISPR/Cas9 system in C57BL/6 inbred strain mice. Mutant mice showed severe attrition of germ cells during foetal development, resulting in depletion of ovarian germ cells before sexual maturation. Comprehensive transcriptome analysis of embryonic day 13.5 primordial germ cells (PGCs) and postnatal day 1 oocytes demonstrated that XYsry--PGCs had already deviated from the developmental process at the mitotic stage. In addition, XYsry--oocytes resulted in meiotic disruption and developmental failure, and the genes related to these processes were significantly changed. This grievous disruption, which caused germ cell deterioration in XYsry--females, was shown to proceed from the germ cells themselves. These results provide novel insight into the germ cell depletion of sex-reversed mice as well as into disorders of sex differentiation in human, such as Swyer syndrome, wherein patients present as typical females albeit with an XY karyotype and infertile.

developmental biology↗

bioRxiv2017

Effect Of Initial Body Orientation On Escape Probability In Prey Fish Escaping From Predators

Since the escape response is crucial to survival and hence to the fitness of species, several studies have attempted to elucidate the kinematic and behavioral components of the response that affect evasion outcome. The preys body orientation relative to a predator at the onset of the escape response (initial orientation) could affect evasion outcome, because the turn angle and its duration before the initiation of escape locomotion would be smaller when the initial orientation is more away from the predator. We tested this hypothesis by recording the escape responses of juvenile red sea bream (Pagrus major) in response to the predatory scorpion fish (Sebastiscus marmoratus) using a high-speed video camera. Our results show that an increased initial orientation (i.e., more away from the predator) increases escape probability. Our results also indicate that an increase in the initial orientation decreases the turn angle and its duration. The flight initiation distance tends to be small when the initial orientation is away from the predator, suggesting that the prey might have a blind zone of sensory perception. These findings highlight the importance of incorporating initial orientation into both empirical and theoretical studies of the kinematics of predator-prey interactions.\n\nSummary statementOur predator-prey experiments reveal that the preys initial body orientation relative to a predator affects the preys turn angle and its duration, and consequently affects escape probability.

animal behavior and cognition↗