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Whole-body endothermy in a mesopelagic fish, the opah, Lampris guttatus

Science  15 May 2015:
Vol. 348, Issue 6236, pp. 786-789
DOI: 10.1126/science.aaa8902

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A cold-water fish with a warm heart

Mammals and birds warm their entire bodies above the ambient temperature. Generally, this ability is lacking in other vertebrates, although some highly active fish can temporarily warm their swim muscles. Wegner et al. show that the opah, a large deepwater fish, can generate heat with its swim muscles and use this heat to warm both its heart and brain. This ability increases its metabolic function in cold deep waters, which will help the fish compete with other, colder-blooded species.

Science, this issue p. 786

Abstract

Endothermy (the metabolic production and retention of heat to warm body temperature above ambient) enhances physiological function, and whole-body endothermy generally sets mammals and birds apart from other animals. Here, we describe a whole-body form of endothermy in a fish, the opah (Lampris guttatus), that produces heat through the constant “flapping” of wing-like pectoral fins and minimizes heat loss through a series of counter-current heat exchangers within its gills. Unlike other fish, opah distribute warmed blood throughout the body, including to the heart, enhancing physiological performance and buffering internal organ function while foraging in the cold, nutrient-rich waters below the ocean thermocline.

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