Limb loss and feeding ability in the juvenile mud crab Scylla olivacea: Implications of limb autotomy for aquaculture practice

Abstract

In Scylla mud crab farming, limb autotomy is commonly used in soft-shell crab production to expedite the moulting process and temporarily achieve high stocking density during crablet transportation. However, little is known about the effect of limb loss on the feeding ability of mud crabs. Therefore, we investigated the effect of various degrees of limb autotomy on the feeding ability of S. olivacea on either live blood cockles or cockle meat, and subsequently the effect of different live cockle size and days after limb removal. The removal of all appendages except for swimming legs compromised S. olivacea’s ability to feed on live cockles but not on cockle meat. When fed with live cockles, the total eaten cockle mass was similar among treatments, but the loss of limbs resulted in lower number of crabs engaged in feeding activity and longer feeding duration. When fed with cockle meat, crabs of all treatments engaged in feeding activity, and only full autotomised crabs showed prolonged feeding duration. Limb loss, but not cockle size nor day after limb removal, affected cockle consumption. Only crabs with one cheliped removed improved their feeding duration after Day 7, whereas crabs that lost both chelipeds did not show change in feeding duration. These results suggest that limb removal affect the feeding ability in mud crabs, and this serves as essential knowledge for future optimisation of the feeding practices of mud crab juveniles right after transportation or during soft-shell crab culture.