Life cycle of Truttaedacnitis stelmioides (Vessichelli, 1910) (Nematoda: Cucullanidae) in American brook lamprey (Lampetra lamottenii)

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Abstract
Field data from two populations of Lampetra lamottenii (Lesueur, 1827) in Ontario, combined with informattion from experimental studies, have provided the following explanation of the transmission of Truttaedacnitis stelmioides (Vessichelli, 1910). Eggs hatch on the stream bed in spring and early summer. Newly hatched larvae are ingested by filter-feeding ammocoetes and remain in the intestine throughout the summer. After developing to the third stage, larvae migrate via the bile duct to cystic ducts of the liver where they remain in a state of arrested development for up to 4 years. During transformation of the host, third-stage larvae apparently moult at least once in the liver, reenter the intestine, and develop to maturity in transformers and adult lampreys. Eggs are released into the lamprey intestine and eventually passed from the anus. Transmission occurs mainly in early summer. Truttaedacnitis stelmioides never becomes encapsulated in the gut wall of L. lamottenii although it may in other lamprey species. Lampetra lamottenii may be the most suitable host among the lampreys. The biology of the parasite is closely linked to the metamorphosis and maturation of the lamprey. Other cucullanids may have a similar relationship with their hosts. Possibly the cucullanids are basically heteroxenous in that they use the immature stage of the host (e.g. the ammocoete) as an intermediate host.
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