Early development of Khawia sinensis Hsü, 1935 (Cestoda: Caryophyllidea), a carp parasite.

The development of the tapeworm Khawia sinensis parasitizing carp (Cyprinus carpio L.) has been studied from the release of cestode eggs into water to the formation of infective procercoids in the intermediate host under laboratory conditions. The rate of embryonal development is greatly influenced by the water temperature. While at 5 degrees C the development of oncospheres was not recorded, at 10-12 degrees C, 15 degrees C, 20-22 degrees C, and 23-24 degrees C oncospheres were fully formed after 57, 42, 21 and 16 days, respectively. Infectivity of oncospheres was confirmed by successful experimental infection of the intermediate hosts: Tubifex tubifex and Limnodrilus udekemiamus (Oligochaeta: Tubificidae). Fully formed procercoids infective for the definitive host were found in the intermediate host from 52 days of development at 20-22 degrees C. From the third week of development in the intermediate host, most of the parasite larvae were located in the anterior part of the tubificid body, mainly between 8th and 15th segments.