Background: The influence of environmental factors, especially temperature, on sex ratio is of great significance to elucidate the mechanism of sex determination. However, the molecular mechanisms by which temperature affects sex determination remains unclear, although a few candidate genes have been found to play a role in the process. In this study, we conducted transcriptome analysis of the effects induced by high temperature on zebrafish during gonad differentiation period. Results: Totals of 1171, 1022 and 2921 differentially expressed genes (DEGs) between high temperature and normal temperature were identified at 35, 45 and 60 days post-fertilization (dpf) respectively, revealing that heat shock proteins (HSPs) and DNA methyltransferases (DNMTs) were involved in the heat-exposed sex reversal. The Gene Ontology (GO) terms and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway that were enriched in individuals after heat treatment included Fanconi anemia (FA) pathway, cell cycle, oocyte meiosis and homologous recombination. Conclusions: Our study provides the results of comparative transcriptome analyses between high temperature and normal temperature, and reveals that the molecular mechanism of heat-induced masculinization in zebrafish is strongly related to the expression of HSPs and DNMTs and FA pathway during gonad differentiation.

Forest musk deer (Moschus berezovskii Flerov), a critically endangered ruminant species, faces extinction risks, with captive populations further threatened by prevalent digestive and immune disorders. This study utilized comparative metagenomic sequencing to assess intestinal microbiota structure and functional profiles between wild populations in Chongqing and Hunan and captive individuals. Wild populations exhibited a Pseudomonadota-dominated gut microbiota (significantly more abundant than in captive counterparts), enriched with lignin-degrading genera Novosphingobium and Acinetobacter. In contrast, the captive group demonstrated increased abundances of Bacillota/Bacteroidota, alongside abnormal proliferation of Escherichia and Clostridium. Both alpha and beta diversity analyses confirmed significant compositional divergences among the three groups, with wild populations maintaining higher diversity than captive populations. Notably, while substantial disparities in microbial abundance existed between wild populations (attributed to habitat vegetation differences), core microbial diversity and carbohydrate metabolic functions exhibited convergence. Functional analyses marked divergences in metabolic pathways: Captive microbiota showed enrichment in translation and glycan metabolism pathways, whereas wild populations displayed pronounced enrichment in immune regulation and environmental sensing pathways. These findings establish a theoretical foundation for optimizing wild population conservation strategies and developing science-based captive management protocols.

Global climate change exerts profound impacts on biodiversity and species distributions, potentially leading to habitat contraction and species extinction. As an endemic near‐threatened species designated under China's National Class II Protected Wildlife, the tufted deer ( Elaphodus cephalophus ) lacks comprehensive predictions regarding its future distribution under climate change. This study employs an optimized MaxEnt model integrated with 19 climatic variables and environmental factors (topography, vegetation, and anthropogenic disturbances) to systematically predict the species' potential habitat distribution across China. Through parameter screening of 248 combinations using the Kuenm package, the optimal model configuration achieved exceptional predictive accuracy (AUC = 0.977 ± 0.002). Key findings include: (1) Current suitable habitats span 145.98 × 10 ⁴ km ² , predominantly clustered in the Sichuan‐Guizhou‐Yunnan mountainous regions and the Qinling‐Daba‐Wuling ranges; (2) Annual precipitation, elevation, slope, temperature annual range, NDVI, and temperature seasonality emerged as the variables that performed best in predicting habitat suitability for tufted deer; (3) Projected habitat areas under future climate scenarios will contract by 21.8%–28.4%, with shrinkage concentrated in eastern low‐elevation zones and expansion toward the eastern Qinghai‐Tibet Plateau; (4) Habitat centroids exhibit significant westward shifts, reaching 141.8 km under SSP585 (2090s). This study provided theoretical foundations for conserving E. cephalophus genetic resources and climate‐adaptive management, emphasizing the urgency to prioritize ecological corridor construction in western Sichuan‐southeastern Tibet.

The forest musk deer (Moschus berezovskii) is a national Class I protected wild animal in China, and the IUCN Red list classifies it as globally endangered. It has significant value in traditional Chinese medicine and spices. However, wild M. berezovskii has faced a severe population decline due to human hunting, habitat loss, and fragmentation. Thus, studying its population size and distribution pattern is of great importance to develop effective conservation measures. Here, we determined the optimal MaxEnt model and used stratified sampling and the fecal pile counting method to predict the population size and potential habitat distribution of wild M. berezovskii in Chongqing using 133 species distribution points and 28 environmental variables. The results were as follows: (1) When the optimal model parameters were RM = 3.5 and FC = LQHPT, it had high model prediction accuracy (AUC = 0.909 ± 0.010, TSS = 0.663). (2) Under various climatic, topographic, vegetation, and anthropogenic disturbance scenarios, M. berezovskii was primarily distributed in northern, eastern, southwestern regions of Chongqing, covering an area of approximately 5562.80 km². (3) The key environmental factors affecting the potential habitat distribution of M. berezovskii were elevation (36.5%), normalized difference vegetation index (NDVI, 16.6%), slope (11.8%), and land-use type (7.6%), whereas climate and anthropogenic disturbance factors had relatively little influence. (4) A population estimation for M. berezovskii identified approximately 928 ± 109 individuals in Chongqing. We recommend prioritizing the preservation of high-altitude habitats and native vegetation to mitigate human interference and minimize road damage. In summary, our results can enhance the understanding of M. berezovskii distribution and provide a basis for effective conservation and management initiatives.

Background: Distant hybridization is an important breeding technique for creating new strains with superior traits by integrating two different genomes. Successful hybridization of Megalobrama amblycephala (Blunt snout bream, BSB, 2n = 48) and Culter alburnus (Topmouth culter, TC, 2n = 48) was achieved to establish hybrid lineages (BT and TB), which provide valuable materials for exploring the mechanisms of distant hybridization fertility. In this study, the gonadal tissue transcriptomes of BSB, TC, BT-F₁, and TB-F₁ were sequenced using Illumina high-throughput sequencing technology to analyze the reproductive characteristics of BT and TB. Results: Differential gene expression analysis showed that the differentially expressed genes in BT vs BSB and BT vs TC were mainly enriched in signaling pathways not directly associated with meiosis. While, the differentially expressed genes of TB vs BSB and TB vs TC were mainly enriched in pathways related to meiosis, and most of them were down-regulated, indicating that meiosis is suppressed in TB. Under-dominance (UD) genes were enriched in pathways related to meiosis and DNA repair in TB. Over-dominance (OD) genes were enriched in MAPK signaling pathway, expression level dominance-BSB (ELD-B) genes were enriched in pathways related to steroid hormone synthesis and expression level dominance-TC (ELD-T) genes were not significantly enriched in any pathway in both BT and TB. Conclusions: These results suggest that meiotic progression may not be affected in BT, whereas it is clearly inhibited in TB. Offspring of M. amblycephala maternal parent may have better genomic compatibility and fertility. Our study provides important information on the molecular mechanisms of breaking reproductive isolation in distantly hybridized fertile lineages.

Heat stress is a major environmental stressor that affects fish metabolism, growth, and death rates. This research examined the impact of dietary rutin addition (0, 100, 300, or 500 mg/kg) for 60 days on juvenile hybrid fish (Carassius auratus cuvieri, WCC, ♀ × Carassius auratus red var, RCC, ♂, WR) (27.97 ± 0.56 g) under heat stress conditions (32 ± 1 °C for 48 h). The analysis focused on blood parameters, oxidative stress biomarkers, and hepatic hsp70 and hsp90 gene expression in WR. The results demonstrated that rutin supplementation elevated blood glucose levels and the liver activities of glutathione reductase, glutathione peroxidase, catalase, and total superoxide dismutase in comparison to the control group. Additionally, rutin supplementation also significantly reduced serum cortisol and hepatic malondialdehyde levels while upregulating hepatic hsp70 and hsp90 gene expression. These findings suggest that rutin supplementation enhances antioxidant responses and alleviates the impact of heat stress on fish physiological and biochemical markers and heat shock protein gene expression.