Site-Finding Behaviour of Fasciola Hepatica (Trematoda), a Parasitic Flatworm

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Abstract
Fasciola hepatica is a trematode parasite of the bile duct of herbivores. Site-finding behaviour of this parasite includes a migration from the duodenum through the abdominal cavity to the liver. This study examines the behaviour of the migrating worms at two stages of the life cycle; NEJ - the stage that penetrates the small intestine, and 48HR - the stage that penetrates the liver. Compared to saline controls, crude extracts of duodenal tissue have greater effects on the behaviour of the NEJs while crude extracts of liver tissue have greater effects on the behaviour of 48HRs. Yet, neither NEJs nor 48HRs migrate up gradients of liver extracts or down gradients of duodenal extracts. Stable chemical gradients are difficult to maintain in the motile abdominal cavity and it is suggested that orientation responses play no part in site-finding behaviour. We propose that the major component of site-finding behaviour of F. hepatica is a passive propulsion of the migrating stages through the viscera and along the body wall to the liver. Fasciola hepatica is a trematode parasite of the bile duct of herbivores. Site-finding behaviour of this parasite includes a migration from the duodenum through the abdominal cavity to the liver. This study examines the behaviour of the migrating worms at two stages of the life cycle; NEJ - the stage that penetrates the small intestine, and 48HR - the stage that penetrates the liver. Compared to saline controls, crude extracts of duodenal tissue have greater effects on the behaviour of the NEJs while crude extracts of liver tissue have greater effects on the behaviour of 48HRs. Yet, neither NEJs nor 48HRs migrate up gradients of liver extracts or down gradients of duodenal extracts. Stable chemical gradients are difficult to maintain in the motile abdominal cavity and it is suggested that orientation responses play no part in site-finding behaviour. We propose that the major component of site-finding behaviour of F. hepatica is a passive propulsion of the migrating stages through the viscera and along the body wall to the liver.

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