Stephanurus dentatus Diesing, 1839 : observations on its parasitic life cycle, excretory system and affinities

Abstract

1. The migratory behaviour of the three parasitic stages of Stephanurus dentatus was studied using oral and percutaneous infection with third-stage larvae, and surgical transplantation of all three stages.2. It was shown that intimate contact with the stomach mucosa was not essential for exsheathment, and that penetration of the intestinal mucosa could precede exsheathment .3. Exsheathment and tissue invasion occurred in a variety of tissues, and in the digestive tract of a wide range of animals. It was suggested that man could be infected. Morphological features that would identify S. dentatus larvae in tissues were outlined.4. After oral infection, third-stage larvae migrated from both the stomach and the intestine via portal veins, mesenteric lymphatics, and also into the peritoneal cavity. The liver became heavily infected and larvae grew more rapidly in this organ than in the lungs or mesenteric lymph nodes.5. After infection via the skin, larvae were shown to migrate extensively in subcutaneous tissues and via the lymphatics; the lungs became heavily infected and very few third-stage larvae reached the liver.6. The somatic distribution of third-stage larvae was not a critical factor in determining subsequent development of the parasite, but it was shown that this stage grew most rapidly in the liver.7. The third moult was described and it was shown to occur in a variety of tissues.8. Fourth-stage larvae are capable of migration; the liver became infected irrespective of the site into which this stage was injected. Furthermore, the liver was the most suitable organ for the growth of this stage. Sexual differentiation occurred during the fourth stage, and the morphological changes in relation to this and the development of the intestine are described. ........