Through a lens sharply
- University of California, Davis, Department of Ophthalmology, 4860 “Y” Street, Suite 2400, Sacramento, CA 95817, USA; irschwab@ucdavis.edu
The blue fin tuna (Thunnus thynnus) is a wide ranging pelagic predator and vastly overexploited food resource with enviable visual mechanisms. As can be seen on the cover, the blue fin tuna provides succulent sashimi, but the animal is extraordinary in several other aspects as well.
Most fish are poikilothermic, and as a result, maintain the temperature of the sea around them. The lower body temperature may penalise such fish because sluggishness and neurological lethargy will accompany lower body temperatures. A poikilothermic predator, then, risks temperature induced languor, as well as poorer optical function during the hunt. To solve this problem, some piscine predators have evolved ingenious thermal mechanisms. The blue fin tuna, nearly at the apex of the food chain, has solved this problem in a curious manner.
Blue fin tuna are not poikilothermic, but endothermic, at least partially. The predatory tuna species will sustain body core temperatures that average 23–26°C; a core temperature which is sometimes as much as 21°C above ambient temperatures. These are not mammalian levels, to be sure, but they are sufficient to ensure …
