Himasthla escamosa n. sp (Digenea: Echinostomatidae) from the Kelp Gull, Larus dominicanus (Charadriiformes: Laridae), on the Patagonian Coast, Argentina

In this article, we describe a new species of Himasthla Dietz, 1909 (Digenea: Echinostomatidae) from Larus dominicanus Lichtenstein (Aves: Laridae) in northern Patagonia, Argentina. We also describe the hosts, localities, and key diagnostic features and the measurements of the so far 25 described species. Of these species, Himasthla militaris, H. leptosoma, H. elongata, H. secunda, H. megacotyla, H. multilecithosa, H. piscicola, H. compacta, H. schachtachtinskoi, H. littorinae, H. continua, H. avosettae, and H. interrupta are similar to H. escamosa n. sp. in having 29 head collar spines. Himasthla leptosoma, H. piscicola, H. multilecithosa, H. interrupta, H. continua, and H. militaris can be differentiated from the new species mainly by the extension of the vitellaria. Himasthla avosettae, H. megacotyla, H. elongata, H. compacta, and H. littorinae have a different size or arrangement (or both) of head collar spines compared with H. escamosa. Himasthla secunda can be distinguished from H. escamosa n. sp. in having a larger body, testes, and ovary and a different position of the ovary. The comparison with H. schachtachtinskoi could not be done because the bibliography was not available. This is the first record of the genus in Argentina and from L. dominicanus.