Classification and patterns of ovarian development in Serangium japonicum

Author of the article:LEI Gao-Ke1,2,3** FU Qiu-Mei1,2,3 DING Xue-Ling1,2,3 ZHENG Yu1,2,3 HE Yu-Xian1,2,3 YAO Feng-Luan1,2,3***

Author's Workplace：1. Institute of Plant Protection, Fujian Academy of Agricultural Sciences, Fuzhou 350013, China; 2. Fujian Key Laboratory for Monitoring and Integrated Management of Crop Pests, Fuzhou 350013, China; 3. Fujian Engineering Research Center for Green Pest Management, Fuzhou 350013, China

Key Words：Serangium japonicum; ovarian development; morphological classification; developmental stages; biological control; ovariole length

Abstract：[Aim] To establish morphological criteria for classifying ovarian development in adult female Serangium japonicum and reveal dynamic patterns in the ovarian development of this species, thereby providing a theoretical foundation for optimizing artificial breeding techniques. [Methods] Microscopic dissection and morphological observation were used to examine ovarian development during the first 30 days post-eclosion. Ovariole length was measured, and oocyte numbers were quantified to establish classification criteria. Correlations among developmental parameters were analyzed. [Results] The reproductive system exhibited typical bilateral symmetry, comprising ovaries, lateral oviducts, a median oviduct, and a spermatheca. Based on ovarian morphology, ovariole length, yolk deposition, and oocyte number, ovarian development was classified into five distinct grades: Stage Ⅰ[transparent period, day 1, ovariole length (477.50 ± 8.17) μm], Stage Ⅱ[growth period, day 2, (569.55 ± 26.20) μm], Stage Ⅲ [yolk deposition period, days 3-5, (939.95 ± 17.34) μm, 12-34 immature oocytes], Stage Ⅳ[peak oviposition period, days 6-28, (1265.82 ± 19.43) μm, 10-48 immature oocytes, 0-7 mature oocytes], and Stage Ⅴ [late oviposition period, days 29-30, (1706.91 ± 42.32) μm, 4-12 immature oocytes]. Significant differences (P < 0.001) were observed among stages in ovariole length, and in immature and mature oocyte number. Ovariole length underwent a three-phase developmental pattern and showed strong positive correlation with days post-eclosion. [Conclusion] The five-grade classification system is scientifically robust, with ovariole length serving as a reliable indicator of developmental stage. These findings provide theoretical support for the mass rearing of S. japonicum Chapin for use as a biological control agent.