Data from: Parasites and a host's sense of smell: reduced chemosensory performance of fathead minnows (Pimephales promelas) infected with a monogenean parasite

1. 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. 2. 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. 3. 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. 4. Differences in EOG responses between
infected and uninfected minnows to both cue types were non-significant at
30 d 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. 5. 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.