Sublethal impairment of respiratory control in plaice (Pleuronectes platessa) larvae induced by UV-B radiation, determined using a novel biocybernetical approach |
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Authors: | J F Freitag H-U Steeger U C Storz R J Paul |
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Institution: | Institut für Zoophysiologie, Westf?lische Wilhelms-Universit?t Münster, Hindenburgplatz 55, D-48143 Münster, Germany, DE
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Abstract: | The increasing amount of UV-B radiation (280 to 320 nm) reaching the earth's surface could endanger transparent fish and
zooplankton in upper water layers. Previous studies on marine fish eggs and larvae focused mainly on the effects of high,
lethal doses of ultraviolet irradiation. Now a sensitive test for accumulated, sublethal impairments of physiological performance
has been established. In developing fish larvae (Pleuronectes platessa L.), the respiratory control responses to hypoxia were evaluated by combining a biocybernetical approach and a novel optical
test system. Before testing respiratory control behavior, the larvae were irradiated with light containing UV-B (test individuals)
or free from it (control individuals). Differences in the physiological reactions of these larvae were detected by biocybernetical
analysis (linear systems analysis) of respiratory control. The analysis was based on the evaluation of changes in ventilatory
rate caused by sinusoidally modulated partial pressures of ambient oxygen. The ventilatory movements of the larvae were recorded,
analyzed and evaluated by video microscopy and digital image processing. After several days of irradiation with moderate UV-B
doses or intensities (8.6 kJ m−2 d−1, corresponding to an irradiance of 0.24 W m−2 for 10 h), sublethal impairments of respiratory control could be detected in plaice larvae by this method; both the linearity
of respiratory control itself and the parameters of linear control behavior were affected by UV-B. Concerning environmental
implications, the results must still be interpreted cautiously, because natural irradiation conditions are more complex than
the artificial regimen. Our biocybernetical approach will be useful for further studies on sublethal impairments of physiological
functions caused by UV-B in fish and other transparent marine or limnic animal groups. In addition, the method could be used
to test the sublethal impact of chemical contaminants.
Received: 4 November 1997 / Accepted: 6 May 1998 |
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