The nematode genus Syncuaria Gilbert, 1927 (Acuariidae) is reported for the first time from Argentina with two species parasitic in Threskiomithidae. Syncuaria plegadisi sp. n. from the white-faced ibis, Ptegadis chihi (Vieillot), is described and figured. The new species differs from known species of Syncuaria by the following characters: absence of lateral alae; cephalic cordons narrow, consisting of cuticular plates dorsally and ventrally invaginated forming a groove; presence of cephalic spines; spicules with simple, rounded distal ends; left spicule two to three times longer than right one; female tail dorsally bent and distance between vulva and anus comparable to tail length. Syncuaria diacantha Petter, 1961, a common parasite of the roseate spoonbill, Plalalea ajaja L., is reported for the first time from Argentina and briefly described. SEM micrographs for both species are provided. Both S. plegadisi sp. n. and S. diacantha were found to co-oeeur in the same locality, but not on the same host, suggesting a high degree of host specificity.
Four species of adult digeneans arc reported from freshwater fishes of two lakes in Neuquén, Patagonia, Argentina. Allocreadium patagonicum sp. n. (Allocreadiidae) is described from the intestine of Percichthys colhuapiensis MacDonagh and Percichthys trucha (Cuvier et Valenciennes) (Percichthyidae) from Lago Aluminé. Three species rcdescribed are: Acanthostomoides apophalliformis Szidat, 1956 (Acanthostomidac) from the intestine of P. colhuapiensis and P. trucha from Lago Aluminé and of Salmo trutta (Linnaeus) (Salmonidae) from Lapo Muechulafquén; Deropegus patagonicus (Szidat, 1956) comb. n. (= Genarches patagonicus Szidat, 1956) (Derogenidae) from the stomach of P. colhuapiensis, P. trucha, Oncorhynchus mykiss (Walbaum) (Salmonidae) and Salvelinus fontinalis (Mitchill) (Salmonidae) from Lago Aluminé and of S. trutta from Lago l luechulafquén; and Austrocreadium papilliferum Szidat, 1956 from the intestine of P. trucha from Lago Aluminé. The genus Polylekithum Arnold, 1934 is considered a synonym of the genus Allocreadium Looss, 1900. The genus Austrocreadium Szidat, 1956 is removed to the family Homalomelridae.