Experimental evidence of chemokinesis in newly hatched cod larvae (Gadus morhua L.) |
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| Authors: | K B Døving M Mårstøl J R Andersen J A Knutsen |
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| Institution: | (1) Section of General Physiology, Department of Biology, University of Oslo, P.O. Box 1051, N-0316 Oslo, Norway;(2) Fjellvegen 15, N-6600 Sunndalsøra, Norway;(3) Section of Marine Zoology, Department of Biology, N-0316 Oslo, Norway;(4) Granveien 4, N-4818 Færvik, Norway |
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| Abstract: | The swimming behaviour of laboratory-reared newly hatched cod larvae (Gadus morhua L.) was observed in a control solution of artificial seawater and in seven solutions, each with a different concentration of arginine (109 to 10-3
M). The behaviour of 20 larvae was analysed in each of the eight solutions; the individual observation time was 1 min. Individual movements were recorded on video and analyzed using a computer-assisted program. The larvae swam in straight lines (a trajectory), rested, moved and started swimming again. For the parameters analyzed, i.e., number of movements, angle between successive trajectories and straightness index, there was no significant difference between the behaviour of the larvae in the different solutions. However, for the larvae in 10-5, 10-4 and 10-3
M arginine solutions, the analyzed parameters, i.e., time active, frequency of trajectories (number of movements exceeding body length), distance swum min-1, length of individual trajectories and trajectory velocity, were all significantly lower than for the larvae in the control solution of artificial seawater and for larvae in the solutions of 10-9, 10-8, 10-7 and 10-6
M arginine. The results show that the mean distance swum by cod larvae min-1 was two to five times longer in artificial seawater without arginine and in the four lower concentrations of arginine than in the three higher concentrations. Scanning micrographs show that newly hatched (pre-feeding) cod larvae possess olfactory organs. It seems reasonalbe to assume that the observed changes in swimming behaviour are mediated by the olfactory sense and are important in the feeding strategy of cod larvae. We suggest that the observed behaviour increases the probability of the larvae localizing patches of prey organisms and remaining in the patch once they have found it. The results show that chemokinesis is a mechanism by which the spatial distribution of fish larvae will be correlated with their prey. |
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