Histological Observation and Functional Gene Expression Analysis of Gonadal Development in Ruditapes philippinarum...

This study employed an artificial greenhouse-based system to enhance gonadal development in the Manila clam, Ruditapes philippinarum. The dynamics of gonadal development and expression patterns of five regulatory genes were analyzed through histological sections and quantitative PCR. Under the controlled conditions (Chlorophyll a: 18.61 ± 1.36 μg/L; temperature: 27.3 ± 2.0 °C), the clams' gonads reached full maturity within approximately one month, underscoring the critical importance of appropriate food availability and temperature. Gene expression analysis revealed sex- and stage-specific patterns. The gonadotropin-releasing hormone (GnRH) gene was more expressed in males at day 7, reaching a significant peak at day 7. In contrast, females exhibited synchronized expression peaks for both estrogen-related receptor (ERR) and 17β-hydroxysteroid dehydrogenase (17β-HSD) at day 14 (p < 0.05). Cytochrome P450 17 (CYP17) exhibited a dynamic, sex-specific profile, with significantly higher levels in males at day 7 but elevated expression in females at day 14 and day 21. Furthermore, doublesex and mab-3-related transcription factor 4-like (Dmrt4-like) showed clear sex-dependent temporal patterns: it peaked early during maturation in males, while in females, the peak occurred significantly later, at day 21 (p < 0.05). These dynamic changes in gene expression were closely synchronized with histological alterations, providing mechanistic insights into the regulation of gonadal maturation in R. philippinarum.