Body Temperature of Lamnoid Sharks

 

Elevation of Body Temperature Above Water Temperature
Water Temp. Muscle Liver Stomach Intestinal Valve Brain
Species* F C F C F C F C F C F C
White Shark
(Carcharodon carcharias)
64-70 18-21 7-9 4-5 13-25 7-14
Shortfin Mako
(Isurus oxyrinchus)
68 20 8 4 4 2 5 3 8 4 5 3
Longfin Mako
(Isurus paucus)
74 23 -1 -0.4

Porbeagle
(Lamna nasus)
52 11 11-15 6-8 5-9 3-5 8-10 4-6 11-16 6-9 5-11 3-6
Salmon Shark
(Lamna ditropis)
46-55 8-13 14-20 8-11 18 10 16 9 23 13 9 5
Basking Shark
(Cetorhinus maximus)
64 18 2 1

Bigeye Thresher
(Alopias superciliosus)
61-70 16-21 3-8 2-4

1

* where - instead of a range of temperatures - only a single value is given, the data represent an average of measured temperatures rather than one absolute measurement.

All living things generate waste heat through metabolic processes taking place in their cells. Large organisms have a large amount of heat-generating tissue relative to heat-radiating surface area. This discrepancy often results in a 'thermal lag', in which metabolic heat is produced more quickly than it can be dissipated. Yet even very large sharks, such as the Basking Shark, are only slightly warmer than the water in which they swim.

Like several of its lamnoid relatives, the White Shark is warm-bodied - its swimming muscles and stomach are maintained at temperatures significantly higher than the surrounding water. This temperature elevation is due to regional modifications to its circulatory system known as retia mirablia, which allow the Great White to retain metabolic heat that most sharks simply lose to the surrounding water.

For warm-bodied sharks, a chief benefit of being able to retain metabolic heat is the ability to extend their range into very cold water. For example, the Bigeye Thresher is able to swim at chill depths, scanning the sunlit surface with its huge, upward-mounted eyes for the silhouette of schooling prey.

Another benefit of warm-bodiedness is increased speed and strength of muscle contraction. In sharks, this may translate to greater sustained swimming speeds. But having a suitably modified circulatory system does not, of itself, guarantee warm-bodiedness. Despite having a well developed retial system, the Longfin Mako does not appear to be warm-bodied. As a consequence, the deep-water Longfin Mako is believed to be less active than its shallow-water close relative, the Shortfin Mako.

All sharks for which we have regional temperature data are warmest in the gut. Having a warm stomach and intestine probably accelerates the rate of food digestion and absorption. Although the Great White exhibits the highest recorded temperature elevation above ambient, it may not be the warmest lamnoid. That distinction probably falls to the Salmon Shark, as its stomach and intestinal temperatures are even higher than its muscle temperature.

Regardless of which shark is warmest, there can be little doubt that the Great White's ability to retain metabolic heat enhances its physiological performance in an aquatic environment notorious for sapping thermal energy at a greedy rate.

 

ReefQuest Centre for Shark Research
Text and illustrations R. Aidan Martin
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