Histological sections for ovary or testis of two mature Toxabramis swinhonis collected in spawning season. Two top figures [(a) and (b)] were ovary containing oogonia (O), perinuclear (P) oocytes, cortical alveolar (CA) oocytes, vitellogenic (V) oocytes, post-ovulatory follicles (POF), luminal cavity (Lc) and lipid vacuoles (Lv). Two bottom figures [(c) and (d)] were testis including spermatogonia (S), spermatocytes (Sc), spermatid (St), spermatozoa (Sz) and luminal cavity (Lc). Stages I to VI were gonadal development stages.