Reproductive biological characteristics of the polychaete Dendronereis chipolini distributed in the Mekong Delta, Vietnam

The reproductive biology of the polychaete Dendronereis chipolini , collected from extensive shrimp ponds in coastal areas of the Mekong Delta, was investigated to provide baseline data for future efforts in artificial reproduction of the species. Live specimens were examined to determine sex differentiation, fecundity, gonadal development, and patterns of embryonic and larval development. Sex was primarily distinguished based on body coloration: mature males exhibited a bright milky green hue, whereas mature females displayed a dark moss green coloration. Absolute fecundity averaged 185,773 ± 76,352 eggs per female, while relative fecundity was 209,520 ± 31,414 eggs per gram of female body weight. Histological analysis revealed four distinct stages of oocyte development, characterized by increasing egg diameters ranging from 40–80 µm (Stage I) to 100–120 µm (Stage IV). Embryonic development, from fertilization to hatching, was completed within 7 hours and 30 minutes at a temperature range of 28–30°C. Larval development proceeded through three stages, Trochophore, Metatrochophore, and Nectochaete, with the final stage exhibiting morphological features resembling adult worms. These findings contribute to the foundational knowledge required for developing reproductive protocols for D. chipolini in aquaculture systems.