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Hybridization is a common technique in the breeding of new varieties. In this study, we obtained F1 and F2 hybrids through interspecific hybridization between Siniperca chuatsi and Siniperca scherzeri and backcross offspring by backcrossing between F1 and Siniperca chuatsi. We analyzed the morphological traits and genetic diversity of the parents and their progeny. The results showed that although most morphological traits of the progeny were not significantly different from those of their parents, the F1 hybrids exhibited the most pronounced morphological variations. The F2 and backcross hybrids appeared morphological differentiation within their populations. The CPL/CPW ratio emerged as a reliable marker for identifying hybrids morphologically. The expected heterozygosity for F1 (0.6264), F2 (0.6677), and backcross offspring (0.5260) were intermediate between Siniperca chuatsi (0.7388) and Siniperca scherzeri (0.3910), indicating a relatively high level of genetic diversity in the offspring. Additionally, the private allele frequency of F1 and F2 was higher than backcross offspring. One SSR marker (G5220) was identified as a specific molecular marker to distinguish the hybrid F1 population from the parents, hybrid F2, and backcross F1 populations by analyzing specific alleles. The result of Ne, He, I, and PIC confirmed that F2 maintained the genetic diversity of F1. We speculated that both F1 and F2 have higher breeding potential. This study provides essential baseline data for genetic breeding of mandarin fish that will be instrumental in the future. [ABSTRACT FROM AUTHOR]

In recent decades, hypoxic areas have rapidly expanded worldwide in estuaries and coastal zones. The Pearl River Estuary (PRE), one of China's largest estuaries, experiences frequent seasonal hypoxia due to intense human activities and eutrophication. However, the ecological effects of hypoxia in the PRE, particularly on fish communities, remain unclear. To explore these effects, we collected fish community and environmental data in July 2021 during the summer hypoxia development period. The results revealed that bottom‐layer dissolved oxygen (DO) in the PRE ranged from 0.08 to 5.71 mg/L, with extensive hypoxic zones (DO ≤ 2 mg/L) observed. Hypoxia has varied effects on fish community composition, distribution, species, and functional diversity in the PRE. A total of 104 fish species were collected in this study, with approximately 30 species (28.6%) exclusively found in hypoxic areas. Species responses to hypoxia varied: species such as Sardinella zunasi, Coilia mystus, and Nuchequula nuchalis were sensitive, while Decapterus maruadsi, Siganus fuscescens, and Lagocephalus spadiceus showed higher tolerance. Within the hypoxia area, dissolved oxygen was the main limiting factor for fish community diversity. Functional diversity (FDiv) decreased with higher dissolved oxygen levels, indicating a potential shift in the functional traits and ecological roles of fish species in response to changing oxygen conditions. Further analysis demonstrated that dissolved oxygen had a significantly stronger effect on fish community structure at hypoxic sites than in the whole PRE. Moreover, other environmental variables also had significant effects on the fish community structure and interacted with dissolved oxygen in the hypoxia area. These findings suggest that maintaining sufficient dissolved oxygen levels is essential for sustaining fish communities and ecosystem health in the PRE. This study provides novel insights into the effects of hypoxia on fish communities in estuarine ecosystems and has significant implications for the ecological health and management of the PRE. [ABSTRACT FROM AUTHOR]

The entire compression system of DGEN380 was selected to study the degradation of aerodynamic characteristics caused by erosion of the leading edge. Numerical simulations under different degrees of leading edge erosion were performed. It was found that the leading edge erosion causes a significant decrease in operability from 70 % of the blade height to the tip, and mainly affects the subsequent flow field in the bypass. At 90 % of blade height, the isentropic efficiency and total pressure ratio of the blade with leading edge erosion are reduced compared to the origin blade. Afterwards, the thrust equation was introduced to analyze the effect of leading edge erosion on the thrust loss under different operating conditions of the aircraft. Among the three operating conditions, the thrust loss rate of the cruise condition was the largest, which provided a reference for the subsequent evaluation of the blade repair condition. [ABSTRACT FROM AUTHOR]

Nitrogen source is one of the important factors that affect the microalgae growth and lipid accumulation. We studied the effects of various nitrogen sources (i.e. NaNO3, CO(NH2)2, NH4Cl and CH3COONH4) and amount on the growth density, lipid yield, and eicosapentaenoic acid (EPA) content of Nannochloropsis oculata by single factor experimental method. The results show that N. oculata preferred NH4+ as nitrogen source rather than NO3- and CO(NH2)2. NH4+ could promote the growth and lipid accumulation of N. oculata. With the increase of nitrogen concentration, the biomass and the content of polyunsaturated fatty acid (PUFA) increased, but the content of lipid decreased. CH3COONH4 was the most suitable for growth, accumulation of lipid and EPA of N. oculata among the four investigated nitrogen sources. The optimal concentration was 5.29 mmol/L.