Tests of host competence
Standard length of each fish was measured, and then a single fish was
stocked in a tank with 0.5 L of dechlorinated tap water. Gyrodactylids
were collected from heavily infected goldfish and two worms were
transferred to the caudal fin of each fish anaesthetized with MS-222 as
described by King and Cable (2007). Following 5 min inoculation, the
caudal fins of 30 individuals of each species were examined using a
stereomicroscope. On day 1 and day 7, gyrodactylids were examined on
caudal fins of these fish anaesthetized with MS-222. If a fish was
infected with at least one gyrodactylid on day 1 and three gyrodactylids
on day 7, it was recorded as attachment success and establishment
success, respectively, which was modified from King and Cable (2007).
Attachment and establishment success rates were calculated as the number
of infected fish divided by the number of exposed fish on day 1 and day
7, respectively. Mean abundance, the mean number of parasites per fish,
infected or not, also was calculated after establishment. If
establishment success rate and mean abundance were significantly lower
than those on the goldfish in the control group, the species was
considered as a low competent host, whereas any species without any
establishment success was defined as an incompetent host.