Knowledge on the reproductive biology of fishes is critical for understanding a species' life history and devising appropriate management strategies. Anthropogenic forces, such as damming and overfishing, threaten fishes endemic to the upper Yangtze River. We conducted a study on the reproductive biology of an endemic species, Ancherythroculter nigrocauda in order to provide information on the life history of this species and to assist in its conservation. From July 2011 to June 2012, a total of 417 fishes were captured via monthly sampling by fishermen in the Longxi River, a tributary in the upper Yangtze River. Although the female-male ratio was 1:1.03, females were predominantly larger in body size. Gonad somatic indices and oocyte diameter distribution showed that the spawning period of A. nigrocauda in the Longxi River ranged from April to August, with the peak in April. Body length at 50 % sexual maturity of A. nigrocauda was estimated to be 125 and 106 mm for females and males, respectively. Absolute fecundity of A. nigrocauda varied between 11,300 and 504,630 eggs, with the mean of 162,377 eggs. In conclusion, A. nigrocauda mature early, spawn once, and are highly fecund, all of which are consistent with an r-selected life history. It is recommended that a moratorium on fishing this species be enacted and the culture of this species be continued.

Microplastics are environmental contaminants and an emergent concern. Microplastics are abundant in freshwater and can cause biochemical stress in freshwater organisms. In the current study, rare minnows (Gobiocypris rarus) were exposed to 1μm polystyrene microplastics at 200 μg/L concentration. We observed various sublethal effects after four weeks of exposure but no mortality. Numerous cellular and tissue alterations were observed in the liver. Differential metabolites and differentially expressed genes between control and exposure groups were identified and mapped to pathways in the Kyoto Encyclopedia of Genes and Genomes. The combination of transcriptomic and metabolomic analyses revealed significantly varied metabolic pathways between the two groups. These pathways were involved in glucolipid, amino acid, and nucleotide metabolism. Results demonstrated that MP exposure induced immune reaction, oxidative stress, and disturbed glycolipid and energy metabolism. The current study provided novel insights into the molecular and metabolic mechanisms of microplastic ecotoxicology in rare minnow.

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