Poecilostomatoida

Order PoecilostomatoidaParasites and commensals of fish and invertebrates; mouth not tubelike or suckerlike; mandibles reduced; adult segmentation often reduced or lost; mostly marine, few freshwater.Order SiphonostomatoidaMouth tubelike or forms a sucker with styletlike mandibles; adult segmentation reduced or lost; parasites and commensals on…