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Diseases of Aquatic Organisms

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DAO 80:21-26 (2008)  -  DOI:

Eye fluke infection and lens size reduction in fish: a quantitative analysis

Anssi Karvonen1,*, Otto Seppälä1,2

1Department of Biological and Environmental Science, University of Jyväskylä, PO Box 35, 40014 Jyväskylä, Finland
2Present address: EAWAG, Department of Aquatic Ecology and ETH-Zürich, Institute of Integrative Biology, Überlandstrasse 133, PO Box 611, 8600 Dübendorf, Switzerland

ABSTRACT: Parasites have a variety of harmful effects on their hosts, some of which may be overlapping or complementary and thus easily overlooked but which are still important for the overall severity of infection. We investigated the effect of Diplostomum sp. eye fluke infection on the size of the eye lens in a range of wild and farmed fish species and those exposed to controlled parasite infection. We found that asymmetry in intensity of infection between the right and left lens of an individual fish affected lens size such that the lens with the higher intensity of infection was smaller. Interestingly, however, this was observed only in 3 of the 10 species studied (whitefish, smelt and sea trout) although in these 3 species the effect had already became evident at low intensities of infection. Furthermore, the average lens size was significantly smaller in experimentally exposed whitefish Coregonus lavaretus with a higher intensity of infection than the controls, emphasising the sensitivity of this species to parasite-induced changes in lens size. Reduction in lens size may contribute to the deleterious effects of cataract formation by intensifying the effects of individual parasites in the lens. It may also directly affect the overall optical performance of the lens and already impair host vision at low intensities of infection.

KEY WORDS: Parasite infection · Trematoda · Lens diameter · Optical performance · Parasite-induced cataracts · Diplostomiasis · Fish farming · Coregonus lavaretus

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Cite this article as: Karvonen A, Seppälä O (2008) Eye fluke infection and lens size reduction in fish: a quantitative analysis. Dis Aquat Org 80:21-26.

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