The gastrointestinal tract of animals contains microbiota, forming a complex microecosystem. Gut microbes and their metabolites can regulate the development of host innate and adaptive immune systems. Animal immune systems maintain intestinal symbiotic microbiota homeostasis. However, relatively few studies have been published on reptiles, particularly snakes, and even fewer studies on different parts of the digestive tracts of these animals. Herein, we used 16S rRNA gene sequencing to investigate the microbial community composition and adaptability in the stomach and small and large intestines of Lycodon rufozonatus. Proteobacteria, Bacteroidetes, and Firmicutes were most abundant in the stomach; Fusobacteria in the small intestine; and Proteobacteria, Bacteroidetes, Fusobacteria, and Firmicutes in the large intestine. No dominant genus could be identified in the stomach; however, dominant genera were evident in the small and large intestines. The microbial diversity index was significantly higher in the stomach than in the small and large intestines. Moreover, the influence of the microbial community structure on function was clarified through function prediction. Collectively, the gut microbes in the different segments of the digestive tract revealed the unique features of the L. rufozonatus gut microbiome. Our results provide insights into the co-evolutionary relationship between reptile gut microbiota and their hosts.

Umami and sweet sensations provide animals with important dietary information for detecting and consuming nutrients, whereas bitter sensation helps animals avoid potentially toxic or harmful substances. Enormous progress has been made toward animal sweet/umami taste receptor (Tas1r) and bitter taste receptor (Tas2r). However, information about amphibians is mainly scarce. This study attempted to delineate the repertoire of Tas1r/Tas2r genes by searching for currently available genome sequences in 14 amphibian species. This study identified 16 Tas1r1, 9 Tas1r2, and 9 Tas1r3 genes to be intact and another 17 Tas1r genes to be pseudogenes or absent in the 14 amphibians. According to the functional prediction of Tas1r genes, two species have lost sweet sensation and seven species have lost both umami and sweet sensations. Anurans possessed a large number of intact Tas2rs, ranging from 39 to 178. In contrast, caecilians possessed a contractive bitter taste repertoire, ranging from 4 to 19. Phylogenetic and reconciling analysis revealed that the repertoire of amphibian Tas1rs and Tas2rs was shaped by massive gene duplications and losses. No correlation was found between feeding preferences and the evolution of Tas1rs in amphibians. However, the expansion of Tas2rs may help amphibians adapt to both aquatic and terrestrial habitats. Bitter detection may have played an important role in the evolutionary adaptation of vertebrates in the transition from water to land.

Microsatellites or simple sequence repeats (SSRs) are prevalent across various organisms' genomes. However, their distribution patterns and evolutionary dynamics in reptile genomes are rarely studied systematically. We herein conducted a comprehensive analysis of SSRs in the genomes of 36 reptile species. Our findings revealed that the total number of SSRs ranged from 1,840,965 to 7,664,452, accounting for 2.16%–8.19% of the genomes analyzed. The relative density ranged from 21,567.82 to 81,889.41 bp per megabase (Mbp). The abundance of different SSR categories followed the pattern of imperfect SSR (I‐SSR) > perfect SSR (P‐SSR) > compound SSR (C‐SSR). A significant positive correlation was observed between the number of SSRs and genome size ( p = 0.0034), whereas SSR frequency ( p = 0.013) or density ( p = 0.0099) showed a negative correlation with genome size. Furthermore, no correlation was found between SSR length and genome size. Mononucleotide repeats were the most common P‐SSRs in crocodilians and turtles, whereas mononucleotides, trinucleotides, or tetranucleotides were the most common P‐SSRs in snakes, lizards, and tuatara. P‐SSRs of varying motif sizes showed nonrandom distribution across different genic regions, with AT‐rich repeats being predominant. The genomic SSR content of the squamate lineage ranked the highest in abundance and variability, whereas crocodilians and turtles showed a slowly evolving and reduced microsatellite landscape. Gene ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analyses indicated that genes harboring P‐SSRs in the coding DNA sequence regions were primarily involved in the regulation of transcription and translation processes. The SSR dataset generated in this study provides potential candidates for functional analysis and calls for broader‐scale analyses across the evolutionary spectrum.

Background: Traditional morphology-based classification of the Oriental Plover (Anarhynchus veredus) is inconsistent with molecular evidence, underscoring the necessity of incorporating molecular data to elucidate its evolutionary relationships within Charadriidae. Methods: Here, we present the first complete mitochondrial genome of A. veredus by Illumina NovaSeq Sequencing and explore its evolutionary implications within Charadriidae. Results: The mitogenome spans 16,886 bp and exhibits conserved structural features typical of Charadriidae, including gene order, overlapping coding regions, and intergenic spacers. Nucleotide composition analysis revealed a GC content of 44.3%, aligning with other Charadriidae species (44.5–45.8%), and hierarchical GC distribution across rRNA, tRNA, and protein-coding genes (PCGs) reflects structural and functional optimization. Evolutionary rate heterogeneity was observed among PCGs, with ATP8 and ND6 showing accelerated substitution rates (Ka/Ks = 0.1748 and 0.1352) and COX2 under strong purifying selection (Ka/Ks = 0.0678). Notably, a conserved translational frameshift in ND3 (position 174) was identified. Phylogenetic analyses (ML/NJ) of 88 Charadriiformes species recovered robust topologies, confirming that the division of Charadriidae into four monophyletic clades (Pluvialis, Vanellus, Charadrius, and Anarhynchus) and supporting the reclassification of A. veredus under Anarhynchus. Conclusions: This study resolves the systematic position of A. veredus and highlights the interplay between conserved mitochondrial architecture and lineage-specific adaptations in shaping shorebird evolution.

Simple sequence repeats (SSRs) are ubiquitous components of eukaryotic genomes that contribute to genome evolution, genetic variation, and gene regulation. Although genome‐wide SSR landscapes have been extensively characterized across vertebrates, the cross‐species distribution and functional associations of exonic SSR‐containing genes remain poorly understood, particularly in non‐model birds. To address this knowledge gap, we performed a comparative analysis of chromosome‐level genome assemblies from three diving duck species ( Aythya ferina , Aythya marila , and Netta rufina ) to investigate genome‐wide SSR patterns and the cross‐species sharing and functional characteristics of exonic SSR‐containing genes. Comparative analyses of genome‐wide SSRs revealed pronounced interspecific variation in SSR abundance and repeat composition, whereas exonic SSR abundance showed more similar values after normalization by total annotated exon sequence length. Cross‐species comparison identified 4336 exonic SSR‐containing genes shared among all three species, greatly outnumbering the species‐specific gene sets. Functional enrichment analyses identified four broad functional themes associated with these shared genes: (i) gene transcription and epigenetic regulation, (ii) protein homeostasis and the ubiquitin–proteasome system, (iii) development, differentiation and morphogenesis, and (iv) stress response and cellular maintenance. The most significantly enriched categories were associated with transcriptional regulation, chromatin remodeling, RNA processing, and epigenetic regulation, whereas autophagy‐ and other cellular‐maintenance pathways indicated additional associations with stress‐response processes. These functional associations should be interpreted cautiously because they may be influenced by cross‐species annotation limitations and gene‐architecture differences. Collectively, our results reveal distinct patterns for genome‐wide and exonic SSRs distribution among the three diving duck species and identify shared functional associations of genes containing exonic SSRs. These findings provide a comparative genomic framework for future investigations of exonic SSRs in waterfowl and other non‐model vertebrates.

The Sand Martin (Riparia riparia) belongs to Hirundinidae. In this study, the complete mitochondrial genome of R. riparia was sequenced and characterized. The genome was 17,963 bases in length (GenBank accession no. OK537984) including 13 protein-coding genes, two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and two control regions. The overall base composition of R. riparia mitogenome was 30.5% for A, 31.8% for C, 14.5% for G, and 23.2% for T. Phylogenetic analysis revealed that R. riparia was genetically closest to the species of genus Tachycineta. R. riparia mitogenome could contribute to our understanding of the phylogeny and evolution of this species.