Levonorgestrel-induced sex reversal in mandarin fish (Siniperca chuatsi): An effective protocol for all-female production and its aquaculture applications.

This study aimed to develop and evaluate an effective protocol for producing all-female populations of mandarin fish (Siniperca chuatsi) through levonorgestrel (LNG)-induced sex reversal of genetic females. During the critical sex differentiation window (15-60 days post hatching), administration of 100 mg/kg LNG through prey-mediated delivery induced 100 % sex reversal of genetic females into functional neo-males, as confirmed by histological and molecular analyses. The neo-males exhibited normal testicular development, complete spermatogenesis, and reproductive competence comparable to XY males. In vivo gene expression analysis revealed that the masculinized state induced by LNG was characterized by the significant upregulation of male-biased genes (dmrt1, gsdf, amh, sox9, and arβ) and the suppression of female-biased genes (foxl2 and cyp19a1a). Furthermore, our in vitro results suggested that LNG could act directly on ovarian cells to induce a similar molecular shift, also modulating reproductive regulation-related genes (fshr and lhr). Crossbreeding experiments demonstrated that the all-female progeny derived from LNG-induced neo-males showed 21 % greater growth performance by 240 dph compared to mixed-sex populations. These findings establish a highly efficient and practical protocol for the production of all-female mandarin fish, demonstrating a valuable application of reproductive technology to enhance aquaculture productivity.