Some Observations and Experiments on the Biology of Larval Trematodes

Abstract

1. Experiments on the liberation of cercariae from their snail hosts have shown that under normal conditions C. limbifera (Seifert) and Cercaria “Z” n.sp. emerge during the day-time only, while in C. cambrensis I (Wright) the emergence takes place during the whole twenty-four hours, but considerably more so during the night-time.Continual darkness causes a decrease in the numbers emerging, and a lowering of the temperature partially or completely checks the escape of the larvae.In Cercaria “Z” there is a double maximum between 11 a.m. and 4 p.m. in the numbers liberated.The invasion of L. truncatula by the larval stages of Fasciola hepatica leads to the disintegration of the host's tissues, the appearance of black pigment and the reduction of the liver cells to a thin layer of protoplasm containing the nuclei.