Abstract
Background
The pot-bellied seahorse (Hippocampus abdominalis) is a high-value marine teleost, but its responses to dietary selenium (Se) remain poorly characterized.Methods
This 70-day trial evaluated nominal nano-selenium (Nano-Se) supplementation levels of 0, 10, 20, and 40 mg/kg; the unsupplemented frozen mysis shrimp contained 0.97 mg Se/kg on a wet-weight basis.Results
Compared with the control, body weight gain and specific growth rate were higher, and feed conversion ratio was lower at 20 and 40 mg/kg. Additionally, body length gain was increased at 10 and 40 mg/kg. Tissue Se concentrations increased with supplementation and were highest in the liver. Nano-Se increased intestinal villus height and digestive enzyme activities; no overt histopathological lesions were observed in the examined sections. Intestinal 16S rRNA gene sequencing identified changes in microbial diversity and taxonomic composition. Untargeted lipidomics identified semi-quantitative changes in hepatic triglyceride-, phospholipid-, and ether-lipid-associated ion signals. Hepatic superoxide dismutase, catalase, and glutathione peroxidase activities were lower in supplemented groups than in the control. Catalase and superoxide dismutase activities were higher at 40 than at 20 mg/kg, whereas glutathione peroxidase did not differ between doses. Steady-state messenger RNA abundances of selenoprotein-related genes and whole-body sex steroid concentrations also changed.Conclusions
Overall, Nano-Se elicited dose- and endpoint-dependent responses, with no single dose consistently superior. The 10-20 mg/kg range warrants further evaluation, whereas 40 mg/kg maximized Se accumulation. These findings provide a basis for refining Nano-Se dose selection in seahorse aquaculture, although the optimal inclusion level and upper safe limit remain unresolved.