Tank bottom area influences the growth, molting, stress response, and antioxidant capacity of juvenile mud crab Scylla paramamosain

Abstract

An 8-week trial was performed to determine the effects of different tank bottom areas (TBA) on growth performance, stress response, and antioxidant capacity of juvenile mud crab Scylla paramamosain. Four treatments in triplicates with different k-value (k = A/CW2, where A is the bottom area (mm2) of the tank, and CW is the carapace width (mm) of the juvenile crab), i.e., k-value = 4.42 (K4), 17.67 (K18), 39.76 (K40), and 70.68 (K70), were used in this experiment. The results showed no significant difference in survival rate (83.33–96.67%) was found, but the K40 group had the best growth performance among all the treatments (P < 0.05). With the decrease of TBA, the level of ecdysone and ecdysone receptor (EcR) gene expression decreased, while the molt inhibitory hormone (MIH) gene expression increased. As a result, prolonged molting intervals and reduced weight gain rates were observed in K4 and K18. Higher cortisol, lactic acid, and lower glycogen content were also observed in K4 (P < 0.05), accompanied by higher phosphofructokinase (PFK) and pyruvate kinase (PK) enzyme activities (P < 0.05). On the contrary, lower catalase (CAT) and higher malondialdehyde (MDA) were observed in the K4 and K18 groups. The results demonstrated that TBA significantly impacted the growth performance of S. paramamosain, and the effects could be mediated through hormonal, glycometabolism, and antioxidant pathways. Notably, the optimal TBA was estimated to be 29.23–59.19 (k-value) according to the quadratic polynomial regression analysis of WGR, and the oversized tank could not give extra benefits in terms of growth performance. Therefore, TBA should be deliberated when designing crab culture facilities.