title: Parasites and a host's sense of smell: reduced chemosensory performance of fathead minnows (Pimephales promelas) infected with a monogenean parasite.
abstract: Parasites residing within the central nervous system of their hosts have the potential to reduce various components of host performance, but such effects are rarely evaluated. We assessed the olfactory acuity of fathead minnows (Pimephales promelas) infected experimentally with the monogenean Dactylogyrus olfactorius, the adults of which live within the host's olfactory chambers. Olfactory acuity was compared between infected and uninfected hosts by assessing electro-olfactography (EOG) neural responses to chemical stimuli that indicate the presence of food (L-alanine) or the presence of conspecifics (taurocholic acid). We also compared differences in gross morphology of the olfactory epithelium in infected and uninfected minnows. Differences in EOG responses between infected and uninfected minnows to both cue types were non-significant at 30 days post-exposure. By days 60 and 90, coincident with a two times increase in parasite intensity in the olfactory chambers, the EOG responses of infected minnows were 70-90% lower than controls. When infected fish were treated with a parasiticide (Prazipro), olfactory acuity returned to control levels by day 7 post-treatment. The observed reduction in olfactory acuity is best explained by the reduced density of cilia covering the olfactory chambers of infected fish, or by the concomitant increase in the density of mucous cells that cover the olfactory chambers. These morphological changes are likely due to the direct effects of attachment and feeding by individual worms or by indirect effects associated with host responses. Our results show that infection of a commonly occurring monogenean in fathead minnows reduces olfactory acuity. Parasite-induced interference with olfactory performance may reduce a fish's ability to detect, or respond to, chemical cues originating from food, predators, competitors or mates.
authors.affiliation: Department of Biological Sciences, University of Lethbridge, Lethbridge, AB, T1K 3M4, Canada.
authors.forename: Ebrahim
authors.identifier: 0000-0002-3623-877X
authors.initials: E
authors.lastname: Lari
authors.affiliation: Department of Biological Sciences, University of Lethbridge, Lethbridge, AB, T1K 3M4, Canada.
authors.forename: Cameron P
authors.initials: CP
authors.lastname: Goater
authors.affiliation: 83 Rhodenizer Lake Rd., Dayspring, NS, B4V 5R7, Canada.
authors.forename: David K
authors.initials: DK
authors.lastname: Cone
authors.affiliation: Department of Biological Sciences, University of Lethbridge, Lethbridge, AB, T1K 3M4, Canada.
authors.forename: Greg G
authors.initials: GG
authors.lastname: Pyle
mesh_terms: D000409:Alanine / Q000378:metabolism; D000818:Animals; D003463:Cues; D003530:Cyprinidae / Q000502:physiology; D005247:Feeding Behavior; D005393:Fish Diseases / Q000469:parasitology / Q000503:physiopathology*; D008297:Male; D009812:Odorants / Q000032:analysis*; D055696:Olfactory Perception; D012903:Smell; D012919:Social Behavior; D013656:Taurocholic Acid / Q000378:metabolism; D014200:Trematoda / Q000502:physiology; D014201:Trematode Infections / Q000469:parasitology / Q000503:physiopathology / Q000662:veterinary*
chemical_list: D013656:Taurocholic Acid; D000409:Alanine
keywords: 
  Dactylogyrus olfactorius
  ; electro-olfactography; fish olfaction; parasitism; pathology