International Journal of Aquaculture, 2024, Vol.14, No.3, 154-164 http://www.aquapublisher.com/index.php/ija 158 Figure 2 Identified spermatogonia types (Adopted from Rozenfeld et al., 2019) Image caption: Forty times magnification fields of selected histological sections representing the spermatogonia stages: the most undifferentiated spermatogonia type A (SPGAund*; panel a), the second most undifferentiated spermatogonia type A (SPGAund; panel b), differentiated spermatogonia type A cells (SPGAdiff; panel c), and early spermatogonia type B cells (SPGB; panel d). These identifiable characteristics are further labeled with arrows: blood vessels (Bv), nucleus (Nu), nucleoli (No), Sertoli cells (Sc), Sertoli cell cytoplasmic extensions (Scce), heterochromatin (Hech), and nuage (Nuage). The results show that the proportion of SPGAdiff cells in the cold seawater treatment group (T10) is significantly higher than in other groups, while the proportion of undifferentiated SPGAund cells is lower, indicating that cold seawater treatment promotes the proliferation and differentiation of spermatogonia (Adapted from Rozenfeld et al., 2019) 5 Promoting Growth 5.1 Nutritional interventions Nutritional interventions play a crucial role in enhancing the growth performance of eels. Various studies have demonstrated the positive effects of dietary supplements on growth metrics. For instance, the inclusion of Chinese herbal medicines mixture (CHMM) in the diet of European eels (Anguilla anguilla) significantly improved weight gain and specific growth rate (SGR) when administered at concentrations of 5-12.5 g/kg (Huang et al., 2020). Similarly, the supplementation of Macleaya cordata extract (MCE) in the diet of juvenile American eels (Anguilla rostrata) at levels of 50 mg/kg or 100 mg/kg resulted in enhanced growth performance and improved intestinal health (Chen et al., 2022). Additionally, the enrichment of eel diets with essential fatty acids from fish oil and corn oil has been shown to significantly increase the growth rate and feed efficiency in Anguilla bicolor (Sari et al., 2019; Ismayanti et al., 2019). 5.2 Growth hormones and supplements Growth hormones and other supplements have been investigated for their potential to enhance growth in eels. The
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