The genetic paradox of biological invasions is complex and multifaceted. In particular, the relative role of disparate propagule sources and genetic adaptation through postintroduction hybridization has remained largely unexplored. To add resolution to this paradox, we investigate the genetic architecture responsible for the invasion of two invasive Asian carp species, bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix) (bigheaded carps) that experience extensive hybridization in the Mississippi River Basin (MRB). We sequenced the genomes of bighead and silver carps (~1.08G bp and ~1.15G bp, respectively) and their hybrids collected from the MRB. We found moderate-to-high heterozygosity in bighead (0.0021) and silver (0.0036) carps, detected significantly higher dN/dS ratios of single-copy orthologous genes in bigheaded carps versus 10 other species of fish, and identified genes in both species potentially associated with environmental adaptation and other invasion-related traits. Additionally, we observed a high genomic similarity (96.3% in all syntenic blocks) between bighead and silver carps and over 90% embryonic viability in their experimentally induced hybrids. Our results suggest intrinsic genomic features of bigheaded carps, likely associated with life history traits that presumably evolved within their native ranges, might have facilitated their initial establishment of invasion,

In this study, loach (Paramisgurnus dabryanus) were fed artificial diets containing 0.31 (control), 0.39, 0.48, 0.50 and 0.62 mg kg(-1) of selenium (Se) for 60 days, respectively. Liver histopathology, hepatocyte ultrastructure, blood indices, biochemical parameters of liver functions and oxidative stress in the Se-treated loach were then assayed. The results showed the following: histopathological and ultrastructural lesions in liver were only observed in loach fed the 0.62 mg Se kg(-1) diet; Haemoglobin and total protein were significantly increased in the 0.50 mg Se kg(-1) group; albumin and high-density lipoprotein were increased significantly in the 0.48-0.50 mg Se kg(-1) groups. However, white blood cell count was significantly decreased in the 0.48 mg Se kg(-1) group; alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase were decreased in the 0.39-0.50 mg Se kg(-1) groups. In liver tissue, the content of hydrogen peroxide was lower than that of controls in the 0.48-0.50 mg Se kg(-1) groups, and the malondialdehyde level was lowest in the 0.48 mg Se kg(-1) group. The activities of superoxide dismutase and glutathione peroxidase were significantly increased in the 0.50 mg Se kg(-1) group; catalase and total antioxidant capacity were markedly increased in the 0.48-0.50 mg Se kg(-1) group. These present results indicated that the dietary Se requirement for loach is 0.48-0.50 mg Se kg(-1) diet.

Lead (Pb(2+)) is a well-known highly toxic element, and Spirodela polyrrhiza is one of the hydrophytes most sensitive to Pb(2+), which might be highly toxic to photosynthesis. However, the mechanism by which Pb(2+) inhibits energy transfer and conversion efficiency remains unclear. Here, we report the effects of Pb(2+) on the secondary structure and function of photosystem II (PS II) of S. polyrrhiza using spectral methods. We found that Pb(2+) accumulated in PS II and damaged its secondary structure, decreased the absorbance of visible light, inhibited energy transfer among amino acids within the PS II protein-pigment complex, and reduced energy transport from tyrosine residue to chlorophyll a. Taken together, Pb(2+) exposure damaged the structure and function of S. polyrrhiza PS II.

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