Effects of photoperiod on gonad development in female Pacific abalone (Haliotis discus hannai)

Abstract

Photoperiod has an impact on the growth and reproduction of marine species. This study assessed whether photoperiod affected the gonad development of Pacific abalone (Haliotis discus hannai), a commercially valuable marine mollusk. Abalone was cultured under three different photoperiodic conditions, 12L:12D (NL group), 18L:6D (LL group), and 24L:0D (WL group) while keeping other conditions constant. There were no significant differences in the survival rates of the three groups. However, compared to the other two groups, the 18L:6D photoperiod indicated a significantly higher gonad index (p ​< ​0.05). The concentrations of 17β-estradiol (E2) and testosterone (T) were also significantly higher in the LL group (p ​< ​0.05). Metabolomics analysis revealed that prostaglandins (PGs), trenbolone acetate (TBA), adenylosuccinic acid, and adenosine 5′-monophosphate were key metabolic indicators essential for fostering gonad development. Quantitative analysis of fatty acid revealed 39 fatty acids in the LL group and lower in the NL group, with arachidonic acid (ARA) being the highest in the LL group. Furthermore, it was found that the metabolite (PG) and genes (PTGR1, COI) involved in the ARA metabolic pathway were significantly highly expressed (p ​< ​0.05) in the LL group, indicating that gonad development in female abalone depended on the ARA metabolic pathway. This study provides a novel understanding of the metabolic pathways involved in the photoperiodic regulation of gonad development in abalone. Furthermore, it enhances the knowledge of abalone reproductive biology and offers scientific data for developing a key technology to regulate rapid and synchronized gonad development in abalone.