The result of scaning electron microscopical examination of filamentous bacteria of Eriocheir sinensis larva is described,and indicated that filamentous bacteria only attach to the surface of Eriocheir sinensis larva and there is no obvious structure extending into the body of larva and filamentous bacteria is schizogenous ,and its nutrition for growing and breeding is absorbed from water milieu.

The tubificidae,one type of metazoa was chosen to control activated sludge bulking which was caused by filamentous bacteria.