Zoological Research最新文献

While the functions of body coloration have been well characterized in many animal taxa, the molecular mechanisms governing its production remain poorly understood. This study investigated the genetic and biochemical basis of yellow body coloration in a mutant form of the Yongzhang golden soft-shelled turtle (YGT, Pelodiscus sinensis), which exhibit a striking yellow phenotype. Comparative pigment analysis revealed that YGTs have significantly lower melanin and higher carotenoid pigmentation compared to atrovirens wild-type turtles (AWTs), while pterin concentrations did not differ between the two groups. Functional validation experiments demonstrated that a single amino acid substitution (I481R) in tyrosinase-related protein 1 ( tyrp1) plays a pivotal role in the reduction of melanin production in YGTs. Expression of tyrp1 from YGTs and AWTs in A375 cells, in which human tyrp1 (h tyrp1) function was depleted by CRISPR-Cas9, led to a specific reduction in melanin production in cells expressing the YGT- tyrp1 variant. Moreover, bco1 and bco2, genes negatively associated with carotenoid content, showed reduced expression in YGTs, suggesting that yellow coloration is achieved through a reduction in melanin pigmentation combined with an accumulation of carotenoids. These findings elucidate the molecular basis of yellow body coloration in turtles and enhance our understanding of pigment regulation in vertebrates.

Cichlid fishes are a textbook example for adaptive radiations, since they diversified into several hundred highly specialized species in each of three great East African lakes. Even scale-eating, an extremely specialized feeding mode, evolved independently multiple times in these radiations and in Lake Tanganyika alone, six endemic scale-eating species occupy this extremely specialized ecological niche. Perissodus microlepis went a step further, by evolving bilaterally asymmetrical heads with an intra-specific polymorphism where left- and right-headed morphs predominantly scrape scales from the opposite sides of their prey. While the bilateral asymmetry of scale-eating cichlids has been known, exactly which craniofacial features explain the laterality of the heads remained unclear. Here we aimed, by utilizing micro-computed tomography (μCT), to resolve this issue of how bilateral symmetry in the skeletal structure is broken in scale-eating Perissodus. Our 3D geometric morphometrics analysis clearly separated and identified the two groups of either left- or right-headed fish. In addition, we observed consistent asymmetric volume changes in the premaxilla, maxilla, and mandible of the craniofacial structures, where left-headed fish have larger jaw elements on the right side, and vice versa. The bimodality implies that the effect sizes of environmental factors might be minor while genetics might be responsible to a larger extent for the asymmetry observed in their head morphology. High-speed video analyses of attacks by asymmetrical morphotypes revealed that they utilize their asymmetrical mouth protrusion, as well as lateralized behavior, to re-orientate the gape towards the preferred side of their prey fish to more efficiently scrape scales.

Probiotic supplementation enhances the abundance of gut-associated Rhodobacteraceae species, critical symbionts contributing to the health and physiological fitness of Litopenaeus vannamei. Understanding the role of Rhodobacteraceae in shaping the shrimp gut microbiota is essential for optimizing probiotic application. This study investigated whether probiotics benefit shrimp health and fitness via the recruitment of Rhodobacteraceae commensals in the gut. Probiotic supplementation significantly enhanced feed conversion efficiency, digestive enzyme activity, and immune responses, thereby promoting shrimp growth. Additionally, probiotics induced pronounced shifts in gut microbial composition, enriched gut Rhodobacteraceae abundance, and reduced community variability, leading to a more stable gut microbiome. Network analysis revealed that the removal of Rhodobacteraceae nodes disrupted gut microbial connectivity more rapidly than the removal of non-Rhodobacteraceae nodes, indicating a disproportionate role of Rhodobacteraceae in maintaining network stability. Probiotic supplementation facilitated the migration of Rhodobacteraceae taxa from the aquatic environment to the shrimp gut while reinforcing deterministic selection in gut microbiota assembly. Transcriptomic analysis revealed that up-regulation of amino acid metabolism and NF-κB signaling pathways was positively correlated with Rhodobacteraceae abundance. These findings demonstrate that probiotic supplementation enriches key Rhodobacteraceae taxa, stabilizes gut microbial networks, and enhances host digestive and immune functions, ultimately improving shrimp growth performance. This study provides novel perspectives on the ecological and molecular mechanisms underlying the beneficial effects of probiotics on shrimp fitness.

Selective regulation of gene expression across distinct brain regions is crucial for establishing and maintaining subdivision identities. DNA methylation, a key regulator of gene transcription, modulates transcriptional activity through the conversion of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC). While DNA methylation is hypothesized to play an essential role in shaping brain identity by influencing gene expression patterns, its direct contribution, especially in primates, remains largely unexplored. This study examined DNA methylation landscapes and transcriptional profiles across four brain regions, including the cortex, cerebellum, striatum, and hippocampus, using samples from 12 rhesus monkeys. The cerebellum exhibited distinct epigenetic and transcriptional signatures, with differentially methylated regions (DMRs) significantly enriched in metabolic pathways. Notably, genes harboring clustered differentially hydroxymethylated regions (DhMRs) overlapped with those implicated in schizophrenia. Moreover, 5mC located 1 kb upstream of the ATG start codon was correlated with gene expression and exhibited region-specific associations with 5hmC. These findings provide insights into the coordinated regulation of cerebellum-specific 5mC and 5hmC , highlighting their potential roles in defining cerebellar identity and contributing to neuropsychiatric diseases.

The progressive impact of Enterocytozoon hepatopenaei (EHP) infection on gut microbial function in Litopenaeus vannamei remains poorly understood beyond static comparisons between healthy and infected individuals. To close this knowledge gap, metagenomic sequencing was used to characterize the gut microbiomes of normal, long, medium, and short-sized adult shrimp categorized by increasing severity of infection. EHP infection suppressed digestive activity while inducing immune responses compared with healthy shrimp. Increasing infection severity was associated with a gradual decline in gut α-diversity and an expansion of potential pathogens and virulence factors (VFs). In addition, dysbiosis in gut microbiota composition and function, as well as reduced network stability among differential species, intensified with infection severity. Accordingly, we identified 24 EHP-discriminatory species that contributed an overall 83.3% accuracy in diagnosing infection severity without false negatives. Functional pathway analysis revealed significant suppression of metabolic, degradative, and biosynthetic processes in EHP-infected shrimp compared with healthy controls. Among them, map00630 glyoxylate and dicarboxylate metabolism and map00280 valine, leucine and isoleucine degradation were consistently depleted in infected individuals, thereby impairing their digestive function and anti-inflammatory responses. Additionally, EHP infection diversified VFs directly affecting shrimp gut microbiome. These findings support a conceptual model linking EHP pathogenesis to the parasite-gut microbiome-shrimp physiology axis.

Avian genomes exhibit compact organization and remarkable chromosomal stability. However, the extent and mechanisms by which structural variation in avian genomes differ from those in other vertebrate lineages are poorly explored. This study generated a diploid genome assembly for the golden pheasant ( Chrysolophus pictus), a species distinguished by the vibrant plumage of males. Each haploid genome assembly included complete chromosomal models, incorporating all microchromosomes. Analysis revealed extensive tandem amplification of immune-related genes across the smallest microchromosomes (dot chromosomes), with an average copy number of 54. Structural variation between the haploid genomes was primarily shaped by large insertions and deletions (indels), with minimal contributions from inversions or duplications. Approximately 28% of these large indels were associated with recent insertions of transposable elements, despite their typically low activity in bird genomes. Evidence for significant effects of transposable elements on gene expression was minimal. Evolutionary strata on the sex chromosomes were identified, along with a drastic rearrangement of the W chromosome. These analyses of the high-quality diploid genome of the golden pheasant provide valuable insights into the evolutionary patterns of structural variation in avian genomes.

Somatic cell nuclear transfer (SCNT) has been successfully employed across various mammalian species, yet cloned animals consistently exhibit low pregnancy rates, primarily due to placental abnormalities such as hyperplasia and hypertrophy. This study investigated the involvement of the Hippo signaling pathway in aberrant placental development in SCNT-induced bovine pregnancies. SCNT-derived cattle exhibited placental hypertrophy, including enlarged abdominal circumference and altered placental cotyledon morphology. RNA sequencing analysis indicated significant dysregulation of Hippo signaling pathway genes in SCNT placentas. Co-expression of YAP1 and CCND1 was observed in cloned blastocysts, placental tissues, and bovine placental mesenchymal stem cells (bPMSCs). Manipulation of YAP1 expression demonstrated the capacity to regulate bPMSC proliferation. Experimental assays confirmed the direct binding of YAP1 to CCND1, which subsequently promoted CCND1 expression in bPMSCs. Furthermore, inhibition of CDK6, a downstream target of CCND1, attenuated SCNT bPMSC proliferation. This study identified YAP1 as a key regulatory component within the Hippo signaling pathway that drives placental hyperplasia in cloned cattle through up-regulation of CCND1-CDK6 expression, facilitating cell cycle progression. These findings offer potential avenues for enhancing cloning efficiency, with implications for evolutionary biology and the conservation of valuable germplasm resources.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive impairment and distinct neuropathological features, including amyloid-β plaques, neurofibrillary tangles, and reactive astrogliosis. Developing effective diagnostic, preventative, and therapeutic strategies for AD necessitates the establishment of animal models that accurately recapitulate the pathophysiological processes of the disease. Existing transgenic mouse models have significantly contributed to understanding AD pathology but often fail to replicate the complexity of human AD. Additionally, these models are limited in their ability to elucidate the interplay among amyloid-β plaques, neurofibrillary tangles, and reactive astrogliosis due to the absence of spatially and temporally specific genetic manipulation. In this study, we introduce a novel AD mouse model (APP/PS1-TauP301L-Adeno mice) designed to rapidly induce pathological symptoms and enhance understanding of AD mechanisms. Neurofibrillary tangles and severe reactive astrogliosis were induced by injecting AAV _DJ-EF1a-hTauP301L-EGFP and Adeno-GFAP-GFP viruses into the hippocampi of 5-month-old APP/PS1 mice. Three months post-injection, these mice exhibited pronounced astrogliosis, substantial amyloid-β plaque accumulation, extensive neurofibrillary tangles, accelerated neuronal loss, elevated astrocytic GABA levels, and significant spatial memory deficits. Notably, these pathological features were less severe in AAV-TauP301L-expressing APP/PS1 mice without augmented reactive astrogliosis. These findings indicate an exacerbating role of severe reactive astrogliosis in amyloid-β plaque and neurofibrillary tangle-associated pathology. The APP/PS1-TauP301L-Adeno mouse model provides a valuable tool for advancing therapeutic research aimed at mitigating the progression of AD.

Animal adaptation to environmental challenges is a complex process involving intricate interactions between the host genotype and gut microbiome composition. The gut microbiome, highly responsive to external environmental factors, plays a crucial role in host adaptability and may facilitate local adaptation within species. Concurrently, the genetic background of host populations influences gut microbiome composition, highlighting the bidirectional relationship between host and microbiome. Despite this, our understanding of gut microbiome plasticity and its role in host adaptability remains limited, particularly in reptiles. To clarify this issue, we conducted a reciprocal translocation experiment with gravid females of the Qinghai toad-headed lizards ( Phrynocephalus vlangalii) between high-altitude (2 600 m a.s.l.) and superhigh-altitude (3 600 m a.s.l.) environments on Dangjin Mountain of the Qinghai-Xizang Plateau, China. One year later, we assessed the phenotypes and gut microbiomes of their offspring. Results revealed significant plasticity in gut microbiome diversity and structure in response to contrasting elevations. High-altitude conditions increased diversity, and maternal effects appeared to enable high-altitude lizards to maintain elevated diversity when exposed to superhigh-altitude environments. Additionally, superhigh-altitude lizards displayed distinct gut microbiome structures with notable host specificity, potentially linked to their lower growth rates. Overall, these findings underscore the importance of the gut microbiome in facilitating reptilian adaptation to rapid environmental changes across altitudinal gradients. Furthermore, this study provides critical insights into microbial mechanisms underpinning local adaptation and adaptative plasticity, offering a foundation for future research on host-microbiome interactions in evolutionary and ecological contexts.

Small RNAs (sRNAs) are a class of molecules capable of perceiving environmental changes and exerting post-transcriptional regulation over target gene expression, thereby influencing bacterial virulence and host immune responses. Pseudomonas plecoglossicida is a pathogenic bacterium that poses a significant threat to aquatic animal health. However, the regulatory mechanisms of sRNAs in P. plecoglossicida remain unclear. This study focused on sRNA113, previously identified as a potential regulator of the fliP gene, a key component of the lateral flagellar type III secretion system. To investigate the effects of sRNA113 on P. plecoglossicida virulence, as well as its role in regulating pathogenic processes and host immune responses, mutant strains lacking this sRNA were generated and analyzed. Deletion of sRNA113 resulted in the up-regulation of lateral flagellar type III secretion system-related genes in P. plecoglossicida, which enhanced bacterial swarming motility, biofilm formation, and chemotaxis ability in vitro. In vivo infection experiments with pearl gentian grouper revealed that sRNA113 deletion enhanced the pathogenicity of P. plecoglossicida. This heightened virulence was attributed to the up-regulation of genes associated with the lateral flagellar type III secretion system, resulting in higher bacterial loads within host tissues. This amplification of pathogenic activity intensified tissue damage, disrupted immune responses, and impaired the ability of the host to clear infection, ultimately leading to mortality. These findings underscore the critical role of sRNA113 in regulating the virulence of P. plecoglossicida and its interaction with host immune defenses. This study provides a foundation for further exploration of sRNA-mediated mechanisms in bacterial pathogenesis and host-pathogen interactions, contributing to a deeper understanding of virulence regulation and immune evasion in aquatic pathogens.