Propulsion mechanism of artificial flagellated micro-swimmers actuated by acoustic waves-theory and experimental verification.

This work examines the acoustically actuated motions of artificial flagellated micro-swimmers (AFMSs) and compares the motility of these micro-swimmers with the predictions based on the corrected resistive force theory (RFT) and the bar-joint model proposed in our previous work. The key ingredient in the theory is the introduction of a correction factorKin drag coefficients to correct the conventional RFT so that the dynamics of an acoustically actuated AFMS with rectangular cross-sections can be accurately modeled. Experimentally, such AFMSs can be easily manufactured based on digital light processing of ultra-violet (UV)-curable resins. We first determined the viscoelastic properties of a UV-cured resin through dynamic mechanical analysis. In particular, the high-frequency storage moduli and loss factors were obtained based on the assumption of time-temperature superposition (TTS), which were then applied in theoretical calculations. Though the extrapolation based on the TTS implied the uncertainty of high-frequency material response and there is limited accuracy in determining head oscillation amplitude, the differences between the measured terminal velocities of the AFMSs and the predicted ones are less than 50%, which, to us, is well acceptable. These results indicate that the motions of acoustic AFMS can be predicted, and thus, designed, which pave the way for their long-awaited applications in targeted therapy.

Metabarcoding of fecal DNA reveals the broad and flexible diet of a globally endangered bird.

Knowing the diet of endangered wild animals is a prerequisite for species-specific conservation and habitat management. The Sichuan partridge Arborophila rufipectus is a globally endangered Galliformes species endemic to the mountains of southwest China. Existing information on the diet of this species is biased and fragmented owing to traditional observation methods. Little is known about their dietary composition or how they respond to temporal variations in food resources throughout the year. In this study, a dietary analysis was performed on 60 fecal samples using DNA Metabarcoding of invertebrates and plants to determine the primary animal and plant components of the diet across 3 critical periods of adult life history (breeding, postbreeding wandering, and overwintering). Preys from the dipteran order, followed by the lepidopteran and araneaen spp., were the predominant, animal-derived foods. Symplocos, Rubus, Celastrus, Holboellia, and Actinidia spp. supply a large abundance of fruits and seeds for this omnivorous bird. Substantial temporal dietary changes among the 3 periods and a general shift toward lower dietary diversity during the breeding season were observed, suggesting that the Sichuan partridge can adjust their diet according to the availability of food resources and their own needs. Characterizing the composition and seasonal changes in Sichuan partridge diets informs the habitat management of native flora (the plant taxa that can generate berries and seeds, such as Symplocos, Rubus, Celastrus, and Holboellia, which are likely of conservation interest) to achieve full life-cycle conservation.

Temporal Variations in the Gut Microbiota of the Globally Endangered Sichuan Partridge (Arborophila rufipectus): Implications for Adaptation to Seasonal Dietary Change and Conservation.

Host-associated microbiotas are known to influence host health by aiding digestion, metabolism, nutrition, physiology, immune function, and pathogen resistance. Although an increasing number of studies have investigated the avian microbiome, there is a lack of research on the gut microbiotas of wild birds, especially endangered pheasants. Owing to the difficulty of characterizing the dynamics of dietary composition, especially in omnivores, how the gut microbiotas of birds respond to seasonal dietary changes remains poorly understood. The Sichuan partridge (Arborophila rufipectus) is an endangered pheasant species with a small population endemic to the mountains of southwest China. Here, 16S rRNA sequencing and Tax4Fun were used to characterize and compare community structure and functions of the gut microbiota in the Sichuan partridges across three critical periods of their annual life cycle (breeding, postbreeding wandering, and overwintering). We found that the microbial communities were dominated by Firmicutes, Proteobacteria, Actinobacteria, and Cyanobacteria throughout the year. Diversity of the gut microbiotas was highest during postbreeding wandering and lowest during the overwintering periods. Seasonal dietary changes and reassembly of the gut microbial community occurred consistently. Composition, diversity, and functions of the gut microbiota exhibited diet-associated variations, which might facilitate host adaptation to diverse diets in response to environmental shifts. Moreover, 28 potential pathogenic genera were detected, and their composition differed significantly between the three periods. Investigation of the wild bird gut microbiota dynamics has enhanced our understanding of diet-microbiota associations over the annual life cycle of birds, aiding in the integrative conservation of this endangered bird. IMPORTANCE Characterizing the gut microbiotas of wild birds across seasons will shed light on their annual life cycle. Due to sampling difficulties and the lack of detailed dietary information, studies on how the gut microbiota adapts to seasonal dietary changes of wild birds are scarce. Based on more detailed dietary composition, we found a seasonal reshaping pattern of the gut microbiota of Sichuan partridges corresponding to their seasonal dietary changes. The variation in diet and gut microbiota potentially facilitated the diversity of dietary niches of this endangered pheasant, revealing a seasonal diet-microbiota association across the three periods of the annual cycle. In addition, identifying a variety of potentially pathogenic bacterial genera aids in managing the health and improving survival of Sichuan partridges. Incorporation of microbiome research in the conservation of endangered species contributes to our comprehensive understanding the diet-host-microbiota relationship in wild birds and refinement of conservation practices.

A bar-joint model based on the corrected resistive force theory for artificial flagellated micro-swimmers propelled by acoustic waves.

In this work, we proposed a bar-joint model based on the corrected resistive force theory (CRFT) for studying artificial flagellated micro-swimmers (AFMSs) propelled by acoustic waves in a two-dimensional (2D) flow field or with a rectangular cross-section. Note that the classical resistive-force theory for 3D cylindrical flagellum leads to over 90% deviation in terminal velocity from those of 2D fluid-structure interaction (FSI) simulations, while the proposed CRFT bar-joint model can reduce the deviation to below 5%; hence, it enables a reliable prediction of the 2D locomotion of an acoustically actuated AFMS with a rectangular cross-section, which is the case in some experiments. Introduced in the CRFT is a single correction factorKdetermined by comparing the linear terminal velocities under acoustic actuation obtained from the CRFT with those from simulations. After the determination ofK, detailed comparisons of trajectories between the CRFT-based bar-joint AFMS model and the FSI simulation were presented, exhibiting an excellent consistency. Finally, a numerical demonstration of the purely acoustic or magneto-acoustic steering of an AFMS based on the CRFT was presented, which can be one of the choices for future AFMS-based precision therapy.

The complete mitochondrial genome of the white-browed laughingthrush Garrulax sannio (Passeriformes: Leiothrichidae).

The complete mitochondrial genome of the white-browed laughingthrush Garrulax sannio was assembled using next-generation sequencing (NGS) technology. The double-stranded circular genome is 17 848 bp in length, including 22 transfer RNAs (tRNAs), 13 protein-coding genes (PCGs), two ribosomal RNAs (rRNAs), and 2 putative control region. All PCGs are initiated with the ATG codon except for COX1 with GTG as its start codon. Five distinct types of stop codons are present, i.e., AGA (ND5), AGG (COX1 and ND1), TAA (ATP6, ATP8, COX2, CYTB, and ND4L), TAG (ND6), and the incomplete codon T/TA (COX3, ND2, ND3, and ND4). The nucleotide composition is moderately asymmetric (28.94% A, 32.82% C, 15.00% G, and 23.24% T) with an overall GC content of 47.82% ("light strand"). Phylogenetic analysis indicated a close genetic relationship between this species and its congeners G. perspicillatus, G. cineraceus, and G. canorus.

The complete mitochondrial genome of the green-backed tit Parus monticolus (Passeriformes: Paridae).

The complete mitochondrial genome of the green-backed tit Parus monticolus was assembled from Illumina sequencing reads. The genome is 16 771 bp long, and harbors 22 transfer RNAs (tRNAs), 13 protein-coding genes (PCGs), two ribosomal RNAs (rRNAs), and one control region. All PCGs are initiated with the ATG codon except for COX1 with GTG as its start codon. Five distinct types of stop codons are inferred, i.e. AGA (ND1 and ND5), AGG (COX1), TAA (ATP6, ATP8, COX2, ND3 and ND4L), TAG (ND6), and the incomplete codon T/TA (COX3, CYTB, ND2 and ND4). The 22 tRNAs range in size from 66 to 75 bp. The 12S and 16S rRNAs are 982 and 1601 bp long, respectively, and are separated by tRNA-Val gene. The putative control region is located between tRNA-Glu and tRNA-Phe with a length of 1187 bp. Phylogenetic analysis indicated that this species is closely related to its congener P. major.

The complete mitochondrial genome of the fulvous parrotbill Paradoxornis fulvifrons (Passeriformes: Muscicapidae).

The complete mitochondrial genome of the fulvous parrotbill (Paradoxornis fulvifrons) has been determined from Illumina sequencing data. The circular genome is 17 059 bp long, comprising 37 genes (13 protein-coding genes/PCGs, 22 tRNA genes and two rRNA genes) and a putative control region. Except for COX1 with GTG as its start codon, all PCGs are initiated with the ATR (ATA/ATG) codons. One PCG (COX1) is terminated with AGG, three PCGs (COX3, ND2 and ND4) with the incomplete stop codon T--/TA-, while all the others with TAA. The 22 tRNAs range in size from 64 bp (tRNA-Ser) to 75 bp (tRNA-Leu). The two rRNAs are 982 bp (12S rRNA) and 1600 bp (16S rRNA) long, respectively. The putative control region is located between tRNA-Thr and tRNA-Pro genes with a length of 1235 bp. The base composition is biased (29.06% A, 31.10% C, 14.97% G and 24.87% T) with an overall A + T content of 53.93% ("light strand"). Phylogenetic analysis indicated that P. fulvifrons is closely related to the congeneric vinous-throated parrotbill (P. webbianus).

The application of temperature data loggers for remotely monitoring the nests of Emei Shan Liocichla (Liocichla omeiensis).

Temperature data loggers (TDL) are mostly used to monitor avian incubation behavior in bird studies. In this paper we demonstrate how TDL can also be used to determine different breeding stages and nest success of the vulnerable Emei Shan Liocichla (Liocichla omeiensis). All nests that contained at least one egg were divided into two groups. Group I included six nests monitored traditionally by the observers' visits, while Group II included eight nests monitored by TDL. Group I and Group II were visited every 1-4 days and 7 days, respectively, to check nest contents and status (e.g., active vs. inactive, and the breeding process) until fledging or nest failure. The time of each observation was recorded to verify the interpretation of TDL. The data recorded by TDL were converted into line graphs of temperature against time and assessed visually. The results indicated that TDL can reliably identify different breeding stages and estimate daily nest survival rates (DSR) and total nest success. The nest success of Group II (0.3015) was higher than that of Group I (0.2387), suggesting that deployment of TDL did not negatively influence nest survival rate of Emei Shan Liocichla. In contrast to traditional nest visits, TDL minimized disturbance by observers and provided a more precise estimate of nest survival. We suggest that TDL should be used more widely in studies of the breeding ecology of rare and endangered birds.