Short term effects of limb autotomy on immune function and disease resistance of Portunus trituberculatus (Brachyura, Portunidae)

Abstract

Abstract Crustaceans usually autotomize their limbs in response to physical or physiological threats. In this study, the short term effects of different degrees of autotomy on immune function and disease resistance of Portunus trituberculatus were studied by autotomizing one limb (mild autotomy) or four limbs (severe autotomy). The results indicate that the total haemocyte count (THC) of these crabs showed a tendency to decrease rapidly at first, then increase, and then decrease after mild autotomy and severe autotomy, but the THC changes for individuals with mild autotomy lagged relatively behind. The haemocyte compositions of the crabs also changed greatly after limb autotomy; especially in the severe autotomy group, the proportion of large granular cells and non-granular cells increased significantly within 0.5 h and 2 h after treatment, and the proportion of small particle cells clearly decreased. From the changes in related immune enzyme activities, the effect of autotomy on the activity of haemolymph superoxide dismutase (SOD) in P. trituberculatus was notably low, but had a greater influence on the activities of phenoloxidase (PO), lysozyme (LZM), acid phosphatase (ACP) and alkaline phosphatase (AKP). Among these activities, PO activity decreased significantly within 1 h after treatment and then gradually recovered, LZM activity began to rise continuously within 4 h of autotomy, and both ACP and AKP activity increased immediately after treatment and then gradually decreased. Compared with the individuals with severe autotomy, the haemolymph immunoenzymatic activity of the mild autotomy crabs was slight and slower. In addition, limb autotomy directly affects the disease resistance of P. trituberculatus, especially for the case of severe autotomy, i.e., the resistance of P. trituberculatus to disease is significantly weakened, and the probability of death greatly increases. On the whole, P. trituberculatus could respond to the short term negative effects of limb autotomy by corresponding physiological regulation mechanisms, but the disease resistance was still reduced. This study showed that the self-regulation ability of P. trituberculatus in response to limb autotomy was limited, especially in the case of severe autotomy.