期刊
JOURNAL OF EXPERIMENTAL BIOLOGY
卷 212, 期 24, 页码 3977-3984出版社
COMPANY OF BIOLOGISTS LTD
DOI: 10.1242/jeb.033282
关键词
thermal neutral zone; lower critical temperature; California sea lion; thermal substitution; swimming energetics
类别
资金
- Brookfield Zoo (Brookfield, IL, USA)
- Sea World (San Diego, CA, USA)
- Alaska SeaLife Center
- Friends of Long Marine Laboratory
- Earl H. Meyers and Ethel M. Meyers Oceanographic and Marine Biology Trust
- American Cetacean Society of Monterey Bay
- American Museum of Natural History Lerner-Gray Fund
- SEASPACE
- Natural Environment Research Council [smru10001] Funding Source: researchfish
As highly mobile marine predators, many pinniped species routinely encounter a wide range of water temperatures during foraging and in association with seasonal, geographical and climatic changes. To determine how such variation in environmental temperature may impact energetic costs in otariids, we determined the thermal neutral zone of adult and juvenile California sea lions (Zalophus californianus) by measuring resting metabolic rate using open-flow respirometry. Five adult female (body mass range. 82.2-107.2 kg) and four juvenile (body mass. 26.2-36.5 kg) sea lions were examined over experimental water temperatures ranging from 0 to 20 degrees C (adults) or 5 to 20 degrees C (juveniles). The metabolic rate of adult sea lions averaged 6.4 +/- 0.64 ml O(2) kg(-1) min(-1) when resting within the thermal neutral zone. The lower critical temperature of adults was 6.4 +/- 2.2 degrees C, approximately 4 degrees C lower than sea surface temperatures routinely encountered off coastal California. In comparison, juvenile sea lions did not demonstrate thermal neutrality within the range of water temperatures examined. Resting metabolic rate of the younger animals, 6.3 +/- 0.53 ml O(2) kg(-1) min(-1), increased as water temperature approached 12 degrees C, and suggested a potential thermal limitation in the wild. To determine whether muscle thermogenesis during activity could mitigate this limitation, we measured the active metabolic rate of juveniles swimming at water temperature (T(water))=5, 12 and 20 degrees C. No significant difference (F=0.377, P=0.583) in swimming metabolic rate was found among water temperatures, suggesting that thermal disadvantages due to small body size in juvenile sea lions may be circumvented by recycling endogenous heat during locomotor activity.
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