STUDIES ON CESTODES OF THE GENUS TRIAENOPHORUS FROM FISH OF LESSER SLAVE LAKE, ALBERTA: IV. THE LIFE OF TRIAENOPHORUS CRASSUS FOREL IN THE SECOND INTERMEDIATE HOST

Abstract

The plerocercoids of Triaenophorus crassus encyst normally in the flesh of fishes of the genus Leucichthys; the whitefishes, Coregonus clupeaformis and Prosopium oregonium, are common alternative hosts in Lesser Slave Lake. Elsewhere lake trout, Cristivomer namaycush, and possibly the inconnu, Stenodus leucichthys, may occasionally serve as hosts.The procercoids arrive in the stomach of their second intermediate host while in the body cavity of Cyclops bicuspidatus. When they are liberated by digestion, the majority apparently enter pyloric caeca, penetrate these, cross the body cavity, and enter the flesh, where encystment as the plerocercoid takes place. The evidence for these movements is only partial. The plerocercoids encyst in the flesh in July each year. They remain three or four years and then disappear by drying up or being reduced to small calcareous nodules.The number of plerocercoids per fish increases with the age of the fish up to five or six years.