Effects of Astaxanthin on Ovarian Development of Largemouth Bass (Micropterus salmoides)

The purpose of the study was to investigate the effects of astaxanthin on ovarian development of largemouth bass (Micropterus salmoides) female. Five isonitrogenous and isolipidic feeds with varying levels of astaxanthin (0.8, 19, 41, 97, and 200 mg/kg) were grouped as AS0, AS20, AS40, AS100, and AS200, respectively. The results indicated that the gonadosomatic index (GSI) was significantly greater in the AS40 and AS100 than in AS0 and AS200 (p < 0.05). The AS40 and AS100 exhibited a dramatically lower hepatosomatic index (HSI) compared to the other groups (p < 0.05). The content of vitellogenin (VTG) was significantly increased in AS100 compared to the AS0, AS20, and AS200 (p < 0.05). Testosterone (T) levels were significantly lower in the AS200 compared to the other groups (p < 0.05). The AS40, AS100, and AS200 groups exhibited significantly greater follicle-stimulating hormone (FSH) levels than the AS0 and AS20 group (p < 0.05). The luteinizing hormone (LH) level was significantly higher in AS100 compared to the other groups (p < 0.05). The estradiol (E₂) levels were significantly higher in AS40 compared to the AS0 and AS200 groups (p < 0.05). The total antioxidant capacity (T-AOC) was significantly higher in AS100 than the AS0 and AS20 groups (p < 0.05). The superoxide dismutase (SOD) activity was significantly higher in AS40 compared to the AS0 and AS200 groups (p < 0.05). The malondialdehyde (MDA) level was significantly decreased in AS40 than the other groups (p < 0.05). Transcriptomic analysis of ovarian tissue revealed that differentially expressed genes primarily involved in pathways such as "ovarian steroidogenesis," "steroid hormone biosynthesis," and "arachidonic acid metabolism." The expression of genes involved in ovarian steroidogenesis and arachidonic acid metabolism, such as cytochrome P450 family 2 subfamily J member (cyp2j), insulin-like growth factor 1 (igf1), phospholipase A2 group (pla2g), FSH receptor (fshr), and acute regulatory protein (star), was significantly upregulated in the AS40 group (p < 0.05). In summary, appropriate amount of astaxanthin supplementation in the diet enhance gonadal development, antioxidant capacity, and sex hormone levels, promote the expression of genes related to gonadal development, and consequently, enhance reproductive performance of largemouth bass.