(Figure 4)
Synonyms: Aploparaksis filiformis Spassky, 1963, pp. 144–146, Figures 37–38 not Aploparaksis filiformis of Hromada and Macko, 1995, pp. 59–60, Figure 4.
Aploparaksis daviesi Deblock and Rausch, 1968, pp. 436–437, Figure 4.
Hosts. Rissa tridactyla (Linnaeus), also shorebirds of the genera Arenaria, Gallinago, Limnodromus.
Intermediate hosts. Styloscolex sokolskayae Morev (Lumbriculidae), Rhyacodrilus coccineus (Vejd) (Tubificidae), Bryodrilus arcticus and Mesenchytraeus sp. (Mesenchytraeidae), experimentally (Bondarenko 1993).
Metacestode. Ramicercus (Bondarenko 1993).
Localities. Russia (Yakutiya, Chukotka, Kamchatka, the Wrangel Island), USA (Alaska, state Washington).
Material studied. Type specimen (USNPC 47086, Rissa tridactyla, St. Lawrence Island, Alaska).
Supplement to the description by Schiller (1951a), based on the type specimen (Figures 4A– D). Scolex 200× 90 mm. Suckers 70–80 mm in diameter. Rostellum 90× 60 mm, rostellar sheath 200× 70 mm. Length of hook 21 mm (length of blade 12, length of base with guard 16 mm); width of hook 10 mm. Testis 100× 60 mm, slightly antiporal. Cirrus sac 205– 230× 25–29 mm, crosses median line. Cirrus reaches 151 mm in length, maximum width in proximal part 8 mm. Approximately one-third of cirrus length covered with relatively large sparsely distributed spines. Seminal receptacle oval, 70× 50 mm, vagina tubular, 110 mm long. Mature uterine proglottides absent.
Remarks. Aploparaksis rissae was known for long only from its original description (Schiller 1951a). Re-examination of the type specimen by Bondarenko (1993) shows that the hermaphroditic proglottis of A. brachyphallos was described and pictured by Schiller as a proglottis of A. rissae. Inaccuracies which have been admitted in the original description of A. rissae did not give any reasons for Spassky (1963), in describing A. filiformis, and Deblock and Rausch (1968), in describing A. daviesi (both species were described from shorebirds), to differentiate them from A. rissae. Bondarenko (1975) first believed that A. daviesi was a synonym of A. filiformis, and later, having investigated type-specimens of both species, came to the conclusion (Bondarenko 1993) that they are similar to A. rissae. For the morphology of A. rissae, and data about its life-cycle, see Bondarenko (1975, 1993).