Testing the systematic position and relationships of Paracreptotrema heterandriae within the Allocreadiidae through partial 28s rRNA gene sequences.

The genus Paracreptotrema Choudhury, Pérez-Ponce de León, Brooks and Daverdin, 2006 (Digenea), comprises 4 species that parasitize poeciliid and cyprinodontid fishes in Middle America. Based on morphological characters exhibited by adults of the type species (Paracreptotrema blancoi Choudhury, Pérez-Ponce de León, Brooks and Daverdin, 2006 ) the genus was tentatively assigned to Allocreadiidae Looss, 1902. We sequenced domains D1-D3 of the 28S rRNA gene of several specimens of Paracreptotrema heterandriae Salgado-Maldonado, Caspeta-Mandujano and Vázquez, 2012 , and analyzed these in a phylogenetic context along with 10 allocreadiid taxa plus several xiphidiatan and 2 monorchiatan digeneans, in order to test the proposed inclusion of P. heterandriae in Allocreadiidae. Maximum likelihood and Bayesian inference analyses of 28S rRNA gene sequences confirmed the classification of Paracreptotrema as an allocreadiid. In the phylogenetic trees, Paracreptotrema appears to be the sister taxon of Creptotrematina aguirrepequenoi Jiménez-Guzmán, 1973, and both are closely related to Auriculostoma Scholz, Aguirre-Macedo, and Choudhury, 2004, with Wallinia Pearse, 1920, as the sister taxon of all these genera; nevertheless, the interrelationships between these 4 genera were not totally resolved. ITS2 sequences of several specimens of P. heterandriae showed null intraspecific variation. Scanning electron microscopy microphotograph demonstrated the presence of 13 and 4 dome-like papillae arranged around the outer and inner edges of the oral sucker, respectively.