Life cycle and geographic distribution of the gymnophallid Bartolius pierrei (Digenea) on the Patagonian coast, Argentina

Abstract

The life cycle of the gymnophallid Bartolius pierrei Cremonte, 2001 (Digenea) at Fracasso Beach (the type locality) (42°25′S, 64°07′W), Península Valdés, Argentina, was elucidated. This digenean uses the clam Darina solenoides (Mactridae) as both first and second intermediate host. The Kelp Gull, Larus dominicanus, and the Red Knot, Calidris canutus rufa, a Neotropical migratory bird, act as definitive hosts. A prevalence of infection of 92% was found in the Red Knot. The cercariae of B. pierrei did not parasitize other invertebrates, not even the tellinid clam Tellina petitiana, which shares the intertidal habitat with D. solenoides. This fact could be explained by the behaviour of the cercaria and its strategy for penetration. The cercariae enter directly in the extrapallial space of the clam by piercing the exposed mantle border. Tellina petitiana could not be invaded by B. pierrei cercariae because it does not expose the mantle border when feeding. Because the Red Knot does not feed on T. petitiana, this behaviour may constitute an adaptive strategy of the parasite. Under laboratory conditions, cercariae lived up to 2 days, metacercariae became infective in 50 days, and the adult life is considerd to be shorter than 3 days. The short adult life span in gymnophallids could be a result of adaptation to migratory birds. This fact would ensure parasite dispersion (i.e. by covering long distances in a short time) and inter-breeding with other Darina-infesting populations located far apart. Bartolius pierrei is an endemic parasite of the Magellan Region, distributed where its intermediate clam host is present, from San José Gulf in Península Valdés to the southern tip of South America.

Keywords:

• Parasite
• Gymnophallidae
• Darina solenoides
• south-west Atlantic coast

Acknowledgements

I wish to express my gratitude to L. O. Bala and his team, for contributing with his knowledge of the feeding ecology of migratory birds, for his help in collecting faecal pellets and for some of the clam samples. I thank E. Topa for histological sections, B. Pión for her help with the translation of a paper from German and P. Dell'Arciprete for her help with the map. I also thank G. Navone and C. Pastor for their constant support. Special thanks are rendered to U. Pardiñas for his invaluable assistance in the field and for his kind and continued help. I am very grateful to P. Bartoli, C. Ituarte and the two anonymous reviewers because the manuscript was greatly improved after their suggestions. The field work was conducted in a Protected Natural Area of Chubut Province with permits from the Secretaría de Turismo y Areas Protegidas. This study was partially funded by a Lerner-Gray Grant (American Museum of Natural History). The author is a member of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET).