Migration and site selection of Ornithodiplostomum ptychocheilus (Trematoda: Digenea) metacercariae in the brain of fathead minnows ( Pimephales promelas).
The migration of subadult parasites to preferred sites within final hosts is well characterized. In contrast, the migration of larval stages of trematodes to specific sites within their second intermediate hosts is poorly understood. We used a serial necropsy approach to characterize the migration of Ornithodiplostomum ptychocheilus diplostomules from the point of cercarial penetration, to encystment within the outermost tissues of the brain of fathead minnows. Diplostomules utilized peripheral nerves to access the central nerve cord, or they used specific cranial nerves to directly access the brain. Within 3 h of exposure to cercariae, 46% of all diplostomules were observed within the medulla of the brain. Diplostomules subsequently utilized specific neural tracts to reach lateral regions of the outermost tissue layer of the optic lobes, the stratum marginale. Diplostomules remained in this layer during their 4-week growth phase, then shifted site to the adjacent meninges for encystment. Characterization of a habitat shift for developing versus encysted metacercariae helps explain the results of previous ecological studies that document transient changes in the effects of metacercariae on the surivival, behaviour, and anti-parasite defences of infected fish.
Matisz
Chelsea E
CE
Department of Biological Sciences, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta, Canada T1K 3M4. chelsea.matisz@uleth.ca
Goater
Cameron P
CP
Bray
Douglas
D
D000818:Animals; D001921:Brain / Q000469:parasitology*; D003530:Cyprinidae / Q000469:parasitology*; D005393:Fish Diseases / Q000469:parasitology*; D006790:Host-Parasite Interactions; D009068:Movement; D014200:Trematoda / Q000502:physiology*; D014201:Trematode Infections / Q000469:parasitology / Q000662:veterinary*