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Juday, Chancey (ed.) / Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XXI (1924)

Pearse, A. S.
The parasites of lake fishes,   pp. [161]-194 PDF (9.5 MB)

Page [161]

                         A. S. PEARSE
  Since the times of Van Beneden and Leuckilart animal parasites
have been intensively studied, but little effort has been made to
determine the amount or frequency of parasitic infection under
natural conditions; except for those species directly related to
man and his domestic animals. Many species of parasites that in-
fest fishes have been, and are being, described, but few accurate
observations that relate to their abundance and the factors which
make them numerous or few have been made.
  Van Cleave (1919) found that half the species of fishes that he
examined from Douglas Lake, Michigan, were infected with acan-
thocephalans, and he determined the percentage of infection for
sixteen species. La Rue (1914), Marshall and Gilbert (1905),
Smallwood (1914), and Ward (1910) made incidental observations
concerning the number of parasites present in certain fishes.
Surber (1913) remarks on the small percentage of natural infee-
-tions-withbgloehidia. The whe crappie, whiM carries  re speciesm
of glochidia than any other fish, he found to show an infection of
only 0.7 per cent, and the sheepshead, known to carry two species
of glochidia, had 3.7 per cent.
  Zschokke (1902) found that salmon lost a large number of their
parasites while migrating up the Rhine. But Ward (1909) points
out that such migrations are not always conducive to parasitic
losses, for the Alaskan salmon during its journey inland acquires
a copepod which is never found in salt water.
  Little is known of the effects of seasonal succession on the life
cycles of the parasites of fishes. Van Cleve (1916) states that
acanthocephalans vary greatly in this respect and cites two species
in one genus which, though occurring in the same host, mature at
different seasons. Hausmann (1897) found that perch had very
few trematodes in the spring. In studying frogs, Ward (1909)
found the lowest percentage of infection in late spring or early

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