The life cycle and geographical distribution of the monorchiid Proctotrema bartolii (Digenea) in the clam Darina solenoides from the Patagonian coast, Argentina.

The life cycle of Proctotrema bartolii Carballo, Laurenti & Cremonte 2011 (Digenea: Monorchiidae) at Fracasso Beach (the type locality) (42°25'S, 64°07'W), Península Valdés, Argentina, was investigated. This digenean uses the clam Darina solenoides (Mactridae) as both the first and second intermediate hosts in the natural environment. The metacercariae were located mainly at the tip of the incurrent siphon, with an infection prevalence of 100%. Experimental infections in other macroinvertebrates, such as the clam Tellina petitiana and the polychaete Glycera americana, were successful, but these and other invertebrates are not naturally infected. Silversides Odontesthes smitti and Odontesthes nigricans (Pisces: Atherinopsidae) and the mullet Eleginops maclovinus (Eleginopidae) act as the definitive hosts of both experimentally and naturally obtained adults. Fish acquire infection by eating either the siphon or the entire clam. Proctotrema bartolii seems to be endemic to the Magellan Region and is distributed where its intermediate clam host is present, from the San José Gulf in Península Valdés to the southern tip of South America.