Effects of glycyrrhizic acid on hatchability, growth, and physiological responses of farmed dojo loach (Misgurnus anguillicaudatus) during early life stages

Abstract

In aquaculture, herbal extracts have been widely tested in multiple fish species due to their safety, low toxicity, and minimal environmental impacts. However, little information is known about the regulatory roles in fish early life stages. Here in the present study, taking dojo loach as an example, we applied glycyrrhizic acid (GA), the most abundant component in licorice root, both in egg hatching and larviculture. GA pre-treatment once at 12.5 mg/L but not 50 mg/L during egg hatching significantly promoted hatchability, thus same dosage were supplemented during Artemia feeding in larviculture. As a positive control, egg yolk was also supplemented during larviculture, resulting in the increased larval body length after 5 days and 10 days. However, GA supplementation even significantly inhibited the body length of loach larvae after 10 days. Further studies indicated the expression pattern of genes involved in growth (GH & IGF-1), early development (PP1, VEGFAa, VIP, & IFT22), nutrient transport (SGLT1, FABP2, & PEPT1), immune (C3–1, Myd88, & IL-1β) and antioxidative responses (SOD, CAT, & GPx) supported the phenotype regarding egg hatchability and larval body length. Thus, our study suggested that the effects of GA and other herbal extracts on fish might vary depending on the dosage and treating period, thus such application should be careful especially during early fish life stages, which may even inhibit fish larval growth performance at inappropriate dosage or period.