Pleistocene climatic oscillations have greatly influenced the evolutionary history and distribution pattern of most extant species. However, their effects on species on the Qinghai-Tibet Plateau (QTP) are not well understood. To investigate the effects of past climatic shifts, particularly the Last Glacial Maximum (LGM), on plateau fish, we analysed the phylogeographic structure and demographic history of five closely related taxa of the subfamily Schizothoracinae, a representative endemic taxon of the QTP, from nine endorheic lakes on the central QTP and three peripheral exorheic rivers using the mitochondrial control region (D-loop) sequence and 12 microsatellite (SSR) markers. Phylogram from D-loop haplotypes revealed two well-supported lineages (North and South) separated by the Tanggula Mountains. The results from the D-loop and SSR revealed that endorheic populations possess high genetic diversity and a unique genetic structure. The most recent demographic expansion occurred post-LGM for most endorheic populations and in the last interglacial period for Siling Co and all exorheic populations. Phylogeographic structure, together with species distribution modelling, supports the scenario of multiple glacial refugia on the QTP during the LGM and suggests that Siling Co (4540 m asl) is a cryptic glacial microrefugia for plateau fish, which would be the highest glacial microrefugia known.

The gut microbiota of fish is crucial for their growth, development, nutrient uptake, physiological balance, and disease resistance. Yet our knowledge of these microbial communities in wild fish populations in their natural ecosystems is insufficient. This study systematically examined the gut microbial communities of seven wild fish species in Chaohu Lake, a fishing-restricted area with minimal water turnover, across four seasons. We found significant variations in gut microbial community structures among species. Additionally, we observed significant seasonal and regional variations in the gut microbial communities. The Chaohu Lake fish gut microbial communities were predominantly composed of the phyla Firmicutes, Proteobacteria(Gamma), Proteobacteria(Alpha), Actinobacteriota, and Cyanobacteria. At the genus level, Aeromonas, Cetobacterium, Clostridium sensu stricto 1, Romboutsia, and Pseudomonas emerged as the most prevalent. A co-occurrence network analysis revealed that C. auratus, C. carpio, and C. brachygnathus possessed more complex and robust gut microbial networks than H. molitrix, C. alburnus, C. ectenes taihuensis, and A. nobilis. Certain microbial groups, such as Clostridium sensu stricto 1, Romboutsia, and Pseudomonas, were both dominant and keystone in the fish gut microbial network. Our study offers a new approach for studying the wild fish gut microbiota in natural, controlled environments. It offers an in-depth understanding of gut microbial communities in wild fish living in stable, limited water exchange natural environments.

Background: Study of the life history traits of any species plays an essential role for understanding their relationship with the surrounding environment and scientific management. The Chinese minnowRhynchocypris oxycephalus, an ecologically and economically important species which was widely distributed in East Asia, is currently diminishing. In the present study, we depicted the main life history traits ofR. oxycephalusfor the first time.Results: A total of 442 individuals were collected from April 2012 to March 2013, with total length (TL) ranging from 32.2 to 158.0 mm. The otolith (lapillus) was proved suitable for age determination. Moreover, the results from marginal increment ratio (MIR) analyses demonstrated its unusual growth pattern: two pairs of opaque and transparent bands were formed each year, which might provide some implications for the age determination of other species. The maximum age for females (4 years) was higher than for males (3 years), while 1- and 2-year-old individuals dominated the population. Both females and males reached maturity at 1 year, and the TL at first maturity was 78.8 mm for females and 60.3 mm for males. Obvious sexual dimorphism was observed as females growing faster and larger than males after maturity. As a multiple spawner,R. oxycephalusreleases batches of eggs from April to August. The fecundity ofR. oxycephaluswas higher, and the size of eggs was larger than that of its closely related species.Conclusions: R. oxycephalusis a short-lived, fast-growing, highly fecund, and early-maturing species; therefore, even a short recovery time after overexploitation or disturbance would be of great use for their restoration. Some life history traits ofR. oxycephalusdemonstrate obvious differences with its closely related species, indicating that latitude and local environment conditions are important selective forces for this species.