Helicometra pisanoae sp.n. [Digenea, Opecoelidae], a parasite of a fish, Trematomus hansoni, in the Eastern Antarctic

Helicometra pisanoae sp. n. (Digenea, Opecoelidae) is described based on adult specimens from a fish, Trematomus hansoni (Nototheniidae) caught at the Adelie Land (Eastern Antarctic). The newly described species belongs to the group of species with the terminal, infundibuliform oral sucker. The other diagnostic features are: the sucker ratio based on mean diameter 1:0.84-1.02, blind intestinal caeca, the genital pore closely anterior to the intestinal bifurcation, the cirrus sac reaching posteriorly to the level of posterior half of the ventral sucker and the vitelline follicles reaching to the level of the ventral sucker.