\u3ci\u3eAlcataenia pygmaeus\u3c/i\u3e sp. n. (Cestoda: Dilepididae) from the Whiskered Auklet, \u3ci\u3eAethia pygmaea\u3c/i\u3e, in the Western Aleutian Islands, Alaska, with a Comment on the Genera \u3ci\u3eAlcataenia\u3c/i\u3e and \u3ci\u3eRissotaenia\u3c/i\u3e

Alcataenia pygmaeus sp. n. is described from whiskered auklets, Aethia pygmaea (Gmelin), from the western Aleutian Islands, Alaska. It is distinguished from its congeners by the overall small size of the strobila and a combination of other characters. The rostellum is armed with 34-38 hooks that measure 41-49 µm in length. The cirrus sac is relatively short, 101-174 µm in length, and reaches or just crosses the poral osmoregulatory canals. There are 36-50 testes located entirely posterior to the female organs. The scolex is deeply embedded in the mucosal tissue of the duodenum of the host. This is the first dilepidid to be recorded from Aethia pygmaea. In addition the genus Rissotaenia Spasskaia and Kolitolova, 1972 was found to be identical to Alcataenia Spasskaia, 1971 and is suppressed as a synonym