Journal
CANADIAN JOURNAL OF ZOOLOGY-REVUE CANADIENNE DE ZOOLOGIE
Volume 86, Issue 8, Pages 790-800Publisher
NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS
DOI: 10.1139/Z08-052
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- Natural Sciences and Engineering Research Council of Canada
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We studied the utilization of air versus water as a respiratory medium for O-2 consumption (Mo-2) in the bimodally breathing African lungfish, Protopterus annectens (Owen. 1839). (151.2 +/- 3.7 g) at 26-28 C. we also investigated the impact of a single meal on this respiratory allocation and nitrogenous waste excretion in lungfish entrained to a 48 h feeding cycle. Correction for the microbial blank was found to be critically important in assessing the aquatic component of Mo-2. After correction, total Mo-2 was low (similar to 1000 mu mol.kg(-1).h(-1)), and lungfish took about 40% of Mo-2 from water and 60% from air. Following a meal of chironomid larvae (3.3% of body mass), Mo-2 values from both air and water increased in proportion over the first 3 h and continued to increase to a peak at 5-8 h postfeeding, at which point total Mo-2 (still 40% from water) was approximately 2.5-fold greater than the prefeeding level. When the same fish, entrained to the same 48 h feeding regime, were fasted. Mo-2 declined then later increased prior to the next anticipated feeding. In fed fish, the elevation in Mo-2 relative to fasted values was approximately 3-fold at 0-3 h and 9-fold at 5-8 h. This specific dynamic action (SDA) effect lasted until 23-26 h and amounted to only 9.5% of the oxycalorific content of the ingested meal. N-waste efflux was only slightly elevated after feeding, where there was a tendency for greater urea-N excretion (significant at 42-48 h): however, the lungfish remained ammoniotelic overall during the 48 h postfeeding period.
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