WALLINIA CHAVARRIAE N. SP. (TREMATODA: MACRODEROIDIDAE) IN ASTYANAX AENEUS (GUNTHER, 1860) AND BRYCONAMERICUS SCLEROPARIUS (REGAN, 1908) (OSTEICHTHYES: CHARACIDAE) FROM THE AREA DE CONSERVACION GUANACASTE, COSTA RICA

Wallinia chavarriae n. sp. is described from the small-bodied characids Astyanax aeneus and Bryconamericus scleroparius in the Area de Conservacion Guanacaste, northwestern Costa Rica. The species differs from W. valenciae in possessing an acetabulum that is smaller than the oral sucker and vitelline follicles that are ovoid or rounded rather than elongate and tubular. Detailed comparison between these 2 species is handicapped by the less than satisfactory condition of the type and only museum specimen of W. valenciae. Wallinia chavarriae and W. valenciae belong to a subfamily of trematodes, Walliniinae, that arguably includes Creptotrematina spp., Magnivitellum simplex, and possibly Margotrema. The morphology of walliniines suggests that they are macroderoidids, but a clearer understanding of their classification could be gained from their larval morphology or from molecular systematic studies. The host associations of a monophyletic Walliniinae would indicate diversification within 2 groups of freshwate...