Triaenophorus nodulosus

Triaenophorus nodulosus, the pike tapeworm, is a species of parasitic cestode (tapeworm) in the family Triaenophoridae. It is known to infect the northern pike, as well as other piscivorous fish, being found in the intestine of its host. It has been found in North America, Europe and England.

Description
Adult specimens of Triaenophorus nodulosus have been seen to range from 70 to 270 mm long. When having a developed egg in the uterus, their maximum width is 1.5 to 4.0 mm. There are four hooks on the scolex, with an angled plate about 112 to 120 um wide and 20 to 30 um deep. Its cirrus sac is 739 to 968 um long.

The eggs of the species are white, but turn brown around 45 minutes after being placed in water. They are ovoid; they are about 58 to 67 um long and 38 to 44 um in diameter. Oncospheres can be made out inside ripe eggs. Coracidia are around the same size of the egg, and are ovoid as well. They are about 67 to 85 um long and 58 to 80 um wide.

Hosts
Triaenophorus nodulosus has been found in a variety of fish, such as the northern pike, the coho salmon, the sockeye salmon, the Great Lakes muskellunge, and the walleye, as well as other fish from the United States and Canada. It uses piscivorous fish as definitive hosts, and uses smaller, preyed-upon fish or other marine organisms, such as copepods in the genus Cyclops, as intermediate hosts. When infecting its hosts, it embeds itself in the intestines or viscera.