Artemia is a genus of halophilic zooplanktons comprising bisexual and parthenogenetic forms, which is an important model for investigating adaption to hypersaline ecosystems. The genus Artemia in China comprises four species: A. sinica, A. tibetiana, A. franciscana and A. parthenogenetica. To investigate the evolutionary relationship of bisexual and parthenogenetic Artemia in China, we analyzed the morphometrics and phylogenetics among twenty-two geographical populations in China. We found significant morphological differentiation across different species and strains of Artemia in China, which exhibited a high level of intra-population variation. We also found overlaps in morphological characteristics between populations, which may raise challenges for the classification of Artemia species using traditional morphological methods. A. franciscana, which originated from various regions in America, was generally distributed along the Chinese coastlines through multiple human introductions. Additionally, native Asian clades split into Western and Eastern Lineages during the late Miocene due to the Himalayan orogeny. Within the Western Lineage, A. tibetiana can be grouped into three taxon units: A. tibeitiana, A. sorgeloosi and A. urmiana. We also found that the distribution and genetic structure of A. sinica were influenced by climate oscillations during the Pleistocene, which might play a pivotal role in driving the formation of parthenogenetic strains in the Eastern Lineage. Overall, our study provides new insight into invertebrate evolution under geographical and climatic impacts in hypersaline environments.

Cefotaxime (CTX) is an easily detectable antibiotic pollutant in the water environment, but little is known about its toxic effects on aquatic invertebrates, especially on the intestine. Here, we determined the oxidative stress conditions of A. sinica under CTX exposure with five concentrations (0, 0.001, 0.01, 0.1 and 1 mg/L) for 14 days. After that, we focused on changes in intestinal tissue morphology and gut microbiota in A. sinica caused by CTX exposure at 0.01 mg/L. We found malondialdehyde (MDA) was elevated in CTX treatment groups, suggesting the obvious antibiotic-induced oxidative stress. We also found CTX exposure at 0.01 mg/L decreased the villus height and muscularis thickness in gut tissue. The 16S rRNA gene analysis indicated that CTX exposure reshaped the gut microbiota diversity and community composition. Proteobacteria, Actinobacteriota and Bacteroidota were the most widely represented phyla in A. sinica gut. The exposure to CTX led to the absence of Verrucomicrobia in dominant phyla and an increase in Bacteroidota abundance. At the genus level, eleven genera with an abundance greater than 0.1% exhibited statistically significant differences among groups. Furthermore, changes in gut microbiota composition were accompanied by modifications in gut microbiota functions, with an up-regulation in amino acid and drug metabolism functions and a down-regulation in xenobiotic biodegradation and lipid metabolism-related functions under CTX exposure. Overall, our study enhances our understanding of the intestinal damage and microbiota disorder caused by the cefotaxime pollutant in aquatic invertebrates, which would provide guidance for healthy aquaculture.

The giant panda (Ailuropoda melanoleuca) is one of the animals with the largest body weight differences between its birth and adult stages, where the newborn cub is 0.1% the size of its mother. The rapid growth of panda cubs has been reported previously, but little is known about the growth pattern of their entire lifetime. In this study, we analyzed body weight records from 206 captive giant pandas collected between 2000 and 2022. The dataset comprised 26,340 measurements, including 12,314 records from 98 males and 14,026 from 108 females, with the oldest male and female being 32 and 37 years old, respectively. Utilizing machine learning, we predicted daily body weights throughout the pandas’ lifespan, allowing us to establish detailed daily normative body weight ranges from birth to advanced age. This study presents the first comprehensive analysis of lifetime body weight distribution in giant pandas, enhancing our understanding of their developmental biology and informing improved body weight management strategies for captive populations.