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First published online January 30, 2009
Journal of Experimental Biology 212, iii (2009)
Copyright © 2009 The Company of Biologists Limited
doi: 10.1242/jeb.029173

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Inside JEB

DEEP-DIVING OPAH HAVE HOT HEADS

Kathryn Knight

kathryn{at}biologists.com

Staying at the top of the food chain takes a lot of effort. Some fish, such as sharks and tunas, have even gone to the extent of warming their brains. Kathryn Dickson from California State University Fullerton, USA, explains that having a warm brain probably allows fast-moving foragers to maintain nervous function and see well as they dive deep in cold waters. But it wasn't clear whether deep-diving squid-chasing opah had gone to the same lengths as other pelagic predators to ensure their place at the top of the pyramid (p. 461).

Catching opah in the Pacific Ocean, the team measured the temperature behind the fish's eyes, in the brain and in the myotomal muscle, and found that the fish's eyes were 2.1°C warmer than the rest of their bodies and their brains were also significantly warmer. They were warming their eyes and brains, much like sharks and tunas.

Curious to find out where the heat was coming from, the team dissected some fish heads and found that one of the muscles attached to the eyeball, the well insulated lateral rectus muscle, was probably the heat source. Closer inspection also showed that the blood flow through the muscle is arranged to minimise heat loss.

So opah seem to warm their brains and eyes, which probably gives them an advantage over their prey when plunging into cold water.

References

Runcie, R. M., Dewar, H., Hawn, D. R., Frank, L. R. and Dickson, K. A. (2009). Evidence for cranial endothermy in the opah (Lampris guttatus). J. Exp. Biol. 212,461 -470.[Abstract/Free Full Text]

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Related articles in JEB:

Evidence for cranial endothermy in the opah (Lampris guttatus)

Rosa M. Runcie, Heidi Dewar, Donald R. Hawn, Lawrence R. Frank, and Kathryn A. Dickson
JEB 2009 212: 461-470. [Abstract] [Full Text]  

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JEB Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Knight, K. Search for Related Content PubMed Articles by Knight, K. Social Bookmarking                         What's this?