Euclinostomum heterostomum (Rudolphi, 1809) (Trematoda): life-cycle, growth and development of the metacercaria and adult

Abstract

The life-history of Euclinostomum heterostomum (Rudolphi, 1809), a clinostomid trematode occurring in the oesophagus and buccal cavity of pond heron Ardeola grayii and cattle egret Bubulcus ibis at Visakhapatnam, India, has been traced from egg to adult stage, based on field and laboratory studies. Eggs released by gravid flukes hatched into miracidia in 10 days. The snail Indoplanorbis exustus served as the first intermediate host and the intramolluscan phase, involving the development of two redial generations and cercariae, took two months. Natural infections with the metacercaria were found in the kidneys and liver of the fish Channa punctatus and muscles of C. orientalis. Laboratory experiments demonstrated that more than 2 months are required for the development of the cercaria into the infective metacercarial stage. The morphology of all of the stages in the life-cycle has been studied in detail, as well as the growth characteristics of the metacercaria within the fish host. Two phases in the metacercarial growth were noted, a lag phase followed by an exponential phase. Allometric growth parameters of body proportions and organs of the metacercaria and the adult are compared. The validity of various species included in the genus Euclinostomum is discussed.