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Induction of stress by the swimbladder nematode Anguillicola crassus in European eels, Anguilla anguilla, after repeated experimental infection

Published online by Cambridge University Press:  31 July 2001

B. SURES
Affiliation:
Zoologisches Institut I Ökologie-Parasitologie, Universität Karlsruhe, Kornblumenstrasse 13, 76128 Karlsruhe, Germany
K. KNOPF
Affiliation:
Institut für Gewässerökologie und Binnenfischerei, Abt. Binnenfischerei, Müggelseedamm 310, 12587 Berlin, Germany
W. KLOAS
Affiliation:
Institut für Gewässerökologie und Binnenfischerei, Abt. Binnenfischerei, Müggelseedamm 310, 12587 Berlin, Germany

Abstract

The purpose of this study was to determine under laboratory conditions over a period of 311 days if infection with the nematode Anguillicola crassus induces stress in European eels (Anguilla anguilla), and stimulates the endocrine stress axis as measured by serum cortisol levels. Eels were experimentally infected with 3rd-stage larvae (L3) in different doses to simulate natural conditions with varying infection pressures. Blood samples were drawn from the caudal vein every 2 weeks and serum cortisol concentrations were determined by radioimmunoassay (RIA). The results showed that the application of L3 resulted in a significant increase in the cortisol levels. The period of time at which elevated cortisol values were observed was consistent with the time of larval development and the appearance of adult A. crassus. Thus, there is a stress response to the larval and young adult stages, but no chronic response to older adults. Therefore, it is likely that infection of eels under natural conditions especially with a high number of larvae may be a considerable stressor, in combination with different environmental factors like water temperature, pH, oxygen concentration, pollution and inter-individual relationships.

Type
Research Article
Copyright
2001 Cambridge University Press

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