Morphological and histological study on the gonadal development of Diptychus maculatus.

Diptychus maculatus is a cold-water fish species inhabiting high-altitude regions, whose populations are declining due to anthropogenic disturbances, and systematic data on its reproductive physiology are scarce. In this study, gonadal developmental characteristics of D. maculatus were clarified through anatomical observation and histological analysis, and a comprehensive six-stage (Ⅰ-Ⅵ) maturity grading system for both sexes was established. The results showed that the ovary exhibited group-synchronous development, which suggests that this species may adopt a total spawning strategy; the oocytes were enclosed by a black egg membrane; oocytes accumulated a large amount of yolk and displayed radial vacuoles. During the development of seminal lobules in the testis, germ cells within each lobule developed synchronously. This study established a detailed histological atlas of the gonads of D. maculatus, elucidated the characteristics of gametogenesis, and provided fundamental data for optimizing artificial breeding programs and formulating scientific fishery management policies.