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Linking high metabolic rates, enhanced cardiac E‐C coupling, and cold tolerance in tunas
Author(s) -
Morrissette Jeff M,
Blank Jason M,
Castilho Pedro C,
Block Barbara A
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a829-a
Subject(s) - yellowfin tuna , biology , thunnus , tuna , serca , zoology , medicine , fishery , atpase , enzyme , biochemistry , fish <actinopterygii>
Tunas are remarkable among teleosts for systemic endothermy, high metabolic rates and exceptional cardiac performance. Among tunas, the 3 bluefin species attain the largest body sizes, inhabit the broadest thermal niches, maintain the warmest body temperatures and experience the coldest ambient temperatures. Measured metabolic rates of bluefin at 20 C (222 ± 24 mgO2/kg/hr) were higher than those of yellowfin tuna (162 ± 19 mgO2/kg/hr). At equivalent swimming speeds tailbeat frequencies of bluefin were 10–17% higher than those of yellowfin tuna. VO2 of bluefin swimming at 1 BL/s was lowest at 15 to 20 C and increased at ambient temperatures of 8 to 10 C and at 25 C. Tropical yellowfin tuna showed a similar pattern, but were unable to tolerate temperatures below 10 C. Interspecific differences in metabolic rate and thermal tolerance correspond with differences in cardiac performance and biochemistry. In situ heart experiments indicate that bluefin tunas maintain higher heart rates and cardiac outputs in the cold than yellowfin tunas. This capacity is linked to increased expression of proteins involved in cardiac excitation‐contraction coupling. Functional Ca2+ uptake measurements, ATP hydrolysis assays and Western blots reveal increased Ca2+ ATPase (SERCA) expression in bluefin cardiac sarcoplasmic reticulum. A similar pattern seems evident for the ryanodine receptor. The cellular and organ traits of bluefin hearts can now be linked to the species’ cold tolerance and higher metabolic rates. Funded by NSF, AHA, Pew Foundation, and Monterey Bay Aquarium.