Modulation of the response of rainbow trout (Oncorhynchus mykiss Walbaum) to confinement, by an ectoparasitic (Argulus foliaceus L.) infestation and cortisol feeding

N. M. Ruane, D. T. Nolan, J. Rotllant, L. Tort, P. H.M. Balm, S. E. Wendelaar Bonga

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    40 Citations (Scopus)

    Abstract

    The effects of a 21 day infestation with the ectoparasite Argulus foliaceus on the response of rainbow trout Oncorhynchus mykiss to an acute stressor (confinement) were investigated. Fish were divided into a control and two parasitized groups, with one parasitized group having received cortisol feeding 72 and 24 h before infection. Prior to confinement only control fish showed a significant increase in body mass and condition factor. Following 4 h confinement, plasma glucose levels in the normal-fed/infested group were significantly higher than in the controls, while the cortisol-fed/infested group had significantly lower plasma levels of adrenocorticotropic hormone (ACTH) and glucose. Both infested groups, but not controls, had higher plasma ACTH and cortisol levels 48 h after confinement when compared with their pre-confinement levels. Stressor-induced immunomodulation was more evident in the parasitized fish after confinement, as was concluded from decreased lysozyme activity, alternative complement activity and oxygen radical production either immediately after, or 48 h post 4 h confinement. Circulating lymphocyte numbers were significantly reduced in the control and normal-fed/infested fish. Results indicate that low ectoparasitic infestations can, for a prolonged period, lead to a stress experience with effects that impair the response to subsequent stressors. Such effects may be further confounded by a previous elevation of plasma cortisol levels.
    Original languageEnglish
    Pages (from-to)43-51
    JournalFish Physiology and Biochemistry
    Volume20
    Issue number1
    DOIs
    Publication statusPublished - 1 Jan 1999

    Keywords

    • Argulus foliaceus
    • Confinement
    • Cortisol feeding
    • Crustacean ectoparasites
    • Immunomodulation
    • Rainbow trout
    • Stress response

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