A significant challenge in aquaculture is the delayed sexual maturation of commercially valuable marine fish, challenging the production of a reliable seed supply. Previous research in various fish species has demonstrated that prolonged treatment with either Follicle-Stimulating Hormone (FSH), Insulin-like Growth Factor 1 (IGF-1), and Estradiol (E2) can induce gonadal development in immature fish. However, current available hormonal treatments, using recombinant proteins, require frequent administration, leading to high costs and labor, and cause stress and mortality to the fish.
This study aimed to test a multi-hormonal treatment with plasmids expressing Seriola FSH and IGF-1 and implants releasing low levels of Estradiol (E2) to induce gametogenesis in the late-maturing female Seriola rivoliana. Successful outcome will ultimately promote sustainable marine aquaculture, especially in species that exhibit late maturation or failure to breed.
One year old female Seriola rivoliana were used for this study. The fish received 0.5 mg/kg BW intramuscular injections of serFSH and/or serIGF-1 expressing plasmids at time 0, 1.5 and 4.5 months. 5 mg E2 implants were administered every 3 months. Gonadal development and circulating FSH and E2 levels were analyzed.
Four months into the experiment, plasma FSH levels were significantly elevated only in the plasmid treatment groups compared to controls (Fig. 1), with no significant difference observed between the double FSH and FSH-IGF-1 plasmid treatments, both administered with an E2 implant. In addition, mid-vitellogenic oocytes were observed across all treatment groups, including the E2 implant group, but were more prevalent in the FSH/IGF-1 treatment group (Fig. 2). These findings suggest that prolonged administration of plasmids expressing FSH and IGF-1, along with E2 implants, can effectively induce gonadal development and trigger precocious puberty.