Swollen hindgut syndrome (SHG) in hatchery-reared Penaeus monodon postlarvae

Abstract

In the course of routine microscopic analysis of hatchery-reared Penaeus monodon postlarvae, several batches were found with hindgut abnormalities not previously described in shrimp postlarvae. The abnormality was named swollen hindgut syndrome (SHG) because it affected mainly the hindgut. Postlarvae with SHG showed enlargement and distention of the hindgut folds and its junction with the midgut, although in some cases swelling also occurred in the midgut of the sixth abdominal segment. Over a five-year period, the yearly prevalence of SHG ranged from 6 to 13% of all batches examined. No seasonal pattern was observed as SHG occurred year-round. Despite the numerous samples obtained, SHG has not been associated with specific predisposing factors in the hatchery. The abnormality caused cessation of the rhythmic movements of the hindgut-midgut junction resulting to failure of affected postlarvae to excrete fecal pellets. Swollen hindgut syndrome, although reversible to some extent, caused mortality and significant size variation within batches of postlarvae resulting in their unsuitability for stocking in grow-out farms.