STUDIES ON CESTODES OF THE GENUS TRIAENOPHORUS FROM FISH OF LESSER SLAVE LAKE, ALBERTA: I. INTRODUCTION AND THE LIFE OF TRIAENOPHORUS CRASSUS FOREL AND T. NODULOSUS (PALLAS) IN THE DEFINITIVE HOST, ESOX LUCIUS

Abstract

Triaenophorus crassus Forel and T. nodulosus (Pallas) occur in the intestine of the northern pike, Esox lucius. T. crassus is deeply imbedded in the gut wall of the host; T. nodulosus is but lightly attached. Pike weighing three pounds or over are more likely to be infected with the former species and smaller pike more often harbour the latter. The greatest number of mixed infections occur in pike around three pounds in weight.T. crassus liberates viable eggs into the host's intestine from the end of April to the middle of May; T. nodulosus is one month later and appears to liberate its eggs directly into the water. Pike are relatively free of T. crassus from mid-May to mid-June and of T. nodulosus in late June and early July.Data presented are interpreted as indicating that the cauda of T. crassus is produced by the progressive degeneration of the plerocercoid beginning at the posterior end.A third, apparently undescribed, species of Triaenophorus was found in the intestine of the pickerel, Stizostedion vitreum.