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Sexually dimorphic plumage coloration is widespread in birds in which the male plumage is brighter than the female. This phenomenon is related to the environmental constraints on sexual selection or intraspecific competition between males and females in birds. The physiological factors and genetic regulation mechanism affecting the color of sexual dimorphism plumages in birds have always attracted significant attention in research. Understanding the diversity of sexually dimorphic traits provides insights into the mating strategies of the sexes and their behavior, ecology, and evolution. Interestingly, the ASIP, MC1R, TYRP1, and BCO2 genes have been identified to play a potential role in the coloration of melanin and carotenoids in bird sexual dimorphism plumages, either by controlling the rate and type of melanin or carotene synthesis or degradation by exerting an effect on the pigment biosynthetic pathway. In this review, we systematically summarize the biological significance, the direct causes (chemical and physical color), and the influence of sex hormones in sexually dimorphic plumage coloration. We also investigate the molecular mechanism underlying the roles of some genes on sexual dimorphism coloration, thereby providing a reference for in-depth understanding on the formation mechanism(s) of sexual dimorphic coloration in birds.鸟类羽毛颜色普遍存在性别二态性,即雄性羽色相对于雌性更鲜艳,这种现象的产生可能与环境对性别的选择效应或性别间的种内竞争有关。鸟类羽毛颜色性别二态性的生理因素及遗传调控机制一直备受关注。了解两性二态性特征的形成机制,有助于深入了解两性的交配策略及种群的行为和进化过程。研究表明,ASIP、MC1R、TYRP1和BCO2等基因能调控鸟类羽色性别二态性的形成,主要通过控制黑色素或胡萝卜素产生或降解的速率和类型,或通过调控色素生物合成途径。本文综述了影响鸟类羽色性别二态性的生物学意义、直接原因(化学性颜色、物理性颜色)、性激素对鸟类羽色性别二态性的影响,以及部分关键基因调控鸟类羽色性别二态性形成的分子机制,以期为深入理解鸟类羽色性别二态性的形成机制研究提供参考。.

Background Photoplethysmographic imaging (PPGi) that is based on camera allows acquiring photoplethysmogram and measuring physiological parameters such as pulse rate, respiration rate and perfusion level. It has also shown potential for estimation of arterial oxygen saturation (SaO2). However, there are some technical limitations such as optical shunting, different camera sensitivity to different light spectra, different AC-to-DC ratios (the peak-to-peak amplitude to baseline ratio) of the PPGi signal for different portions of the sensor surface area, the low sampling rate and the inconsistency of contact force between the fingertip and camera lens. Methods In this paper, we take full account of the above-mentioned design challenges and present an accurate SaO2 estimation method based on two cameras. The hardware system we used consisted of an FPGA development board (XC6SLX150T-3FGG676 from Xilinx), with connected to it two commercial cameras and an SD card. The two cameras were placed back to back, one camera acquired PPGi signal from the right index fingertip under 660 nm light illumination while the other camera acquired PPGi signal from the thumb fingertip using an 800 nm light illumination. The both PPGi signals were captured simultaneously, recorded in a text file on the SD card and processed offline using MATLAB®. The calculation of SaO2 was based on the principle of pulse oximetry. The AC-to-DC ratio was acquired by the ratio of powers of AC and DC components of the PPGi signal in the time–frequency domain using the smoothed pseudo Wigner–Ville distribution. The calibration curve required for SaO2 measurement was obtained by linear regression analysis. Results The results of our estimation method from 12 subjects showed a high correlation and accuracy with those of conventional pulse oximetry for the range from 90 to 100%. Conclusions Our method is suitable for mobile applications implemented in smartphones, which could allow SaO2 measurement in a pervasive environment.