Development of immune functionality in larval and juvenile crimson snapper Lutjanus erythropterus (Bloch 1790)

Ontogenetic development of the immune system in crimson snapper (Lutjanus erythropterus Bloch 1790) larvae was histologically and enzymatically studied from hatch to 36 days post-hatch (DPH). Primitive hepatopancreas appeared on 2 DPH and renal tubules started hematopoiesis on 4 DPH. The spleen anlage appeared on 6 DPH and the thymus formed on 14 DPH. Total activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and sodium-potassium adenosine triphosphatase (Na⁺ K⁺-ATPase) gradually increased after hatch, and showed a sharp increase after 29 DPH during the transitional feeding period from Artemia to inert feed. The specific activities of SOD, CAT, and GPX showed a trend of sharp increase and reached the maximum level on 4 DPH when exogenous feeding started, except for Na⁺ K⁺-ATPase where the peak occurred on10 DPH. The specific activities of these five enzymes reached the peak during the food transition from rotifers to Artemia, but the total activity of enzymes showed an increasing trend as fish grew. The present study provides new knowledge of the development of functional enzymes relevant to fish larvae immunity, sheds light on the understanding of the change of larval health, and improves hatchery management of crimson snapper.