The development of Gymnophallus australis Szidat, 1962 (Digenea: Gymnophallidae) from the Patagonian coast (Argentina) from metacercaria to adult, with an amended diagnosis of Gymnophallus Odhner, 1905
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Parvatrema australis (Szidat, 1962) Szidat, 1965 was described based on larval stages found in specimens of the mussel Mytilus edulis from the Buenos Aires Province, Argentina. Although Szidat later examined hundreds of mussels, this parasite has never been found again until now. In the present study, larval stages, including germinal sacs, found in mytilids from the Patagonian coast were identified as P. australis. Metacercariae were incubated in vitro at 39°C in physiological solution for 18–20 hours, by which time 80% of the specimens had eggs. P. australis is redescribed, on the basis of infective metacercariae and adults obtained in the laboratory, and is reassigned to Gymnophallus Odhner, 1900, the genus in which it was originally described. The generic diagnosis of Gymnophallus is here amended to include as diagnostic characters the presence or absence of the lateral lips, the form and position of the vitellarium (compact or follicular) and the presence of a pars prostatica (i.e. prostatic cells open into proximal part of the ejaculatory duct). The validity of some characters (i.e. the presence of lateral lips of the oral sucker, the form of the vitellarium and excretory vesicle, the extent of the uterus) as diagnostic at the generic level within the family Gymnophallidae is discussed. It is proposed that the least unambiguous characters that can be used to distinguish gymnophallid genera include the position of the ovary, the presence of a ventral pit and a pars prostatica, and caecal diverticula.
KeywordsSeminal Vesicle Ventral Sucker Oral Sucker Genital Pore Ejaculatory Duct
The authors express their gratitude to Javier Klaich, Graciela Escudero and other people from the Centro Nacional Patagónico, who collaborate in sampling activities, and Patricia Sarmiento (from the Museo de La Plata SEM unit) for her advice and technical assistance in the preparation of metacercariae for SEM. Special thanks are owed to Pierre Bartoli (Centre d’Océanologie de Marseille) for a critical revision of the manuscript and for his marvellous work on gymnophallids, which were a guide for this work. The authors also thank both anonymous reviewers for their suggestions that improve the manuscript. The present study was funded by the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (projects Nos PIP 5990 and 5653) and the Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT) (Project Nos. PICT 01–11902 BID 1728/OC-AR). F.C. and C.I. are members of CONICET.
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