Changes in gut evacuation time of larval mud crab, Scylla serrata (Crustacea: Portunidae) fed artificial plankton or live food

To understand the feeding and digestive strategies of Scylla serrata larva and juvenile atvarious stages, gut evacuation time (GET) at different developmental stage were determined in thepresent study. GET in larval S. serrata ranged from 80 min in early zoeal stages to about 120–135 minin megalopa and crab first instar stages. GET differed significantly between stages and between diet butthe interaction of stage and diet was not significant. GET for the artificial food is significantly longer thanthat for the live food. Movement of both the artificial (AF) and live food (LF) along the gut were tracedfrom the hepatopancreas (HP) to the 2nd, 3rd, 4th and 5th abdominal segments (A.S.), midgut (MG),hindgut (HG), near telson and during evacuation. There were very slight differences between themovement of both food at Z1 and Z2. Starting from Z3 to Z5, LF moved faster than the AF but at themegalopa stage, both foods moved from HP to the 5th A.S. at the same time; the AF group exhibiteddelayed movement from MG until evacuation. At the C1 stage, both foods were only visible at the MGand their separation in time became marked i.e. the AF moving markedly slower than did the LFexhibiting GET values of 135 and 120 min, respectively. Thus, it appeared that the feeding strategy ofthe S. serrata larvae and juvenile modulated GET and digestive enzyme activities in response to theapparent digestibility of food presented.