Lesions associated with Philometroides huronensis (Nematoda: Philometridae) in the white sucker (Catostomus...

Lesions associated with Philometroides huronensis in the white sucker (Catostomus commersoni) of southern Ontario occurred during the spring (April-June) and were related to the development and release of first-stage larvae from the gravid nematode. With movement of the subgravid female into the membranous region of the fin, subepidermal tissues were mechanically disrupted and compacted near the nematode. Gravid females were encapsulated by fibrous tissue. Release of first-stage larvae from the gravid nematode was facilitated by a cutaneous opening, disruption of the fibrous capsule and rupture of the nematode. An acute local inflammatory response was associated with this function. Spent nematodes were sequestered and resorbed.