Why is fish cold blooded

This is some of the first direct evidence of the evolutionary advantage of being warm-blooded. This extra speed provides advantages when it comes to things like predation and migration. The faster swim speeds also aid the fish in identifying prey. The quicker they swim, the faster an image moves across their eye, allowing them to process and identify the image — perhaps of prey — faster than slower counterparts. It has previously been suggested that these warm-blooded fishes may be better able to deal with changing ambient temperatures by stabilising their body temperatures.

This would be useful under current climate change scenarios, such as global ocean warming. This means we may have been overstating the resilience warm-blooded fish have for facing changing ocean temperatures. Many of these animals are already facing threats from ocean warming, and human-induced risks. The Atlantic bluefin tuna is an endangered species while the white shark is classed as vulnerable.

Then there are homeotherms and poikilotherms. An organism that is homeothermic maintains a relatively stable body temperature—sometimes through metabolism, or sometimes through its behavior think of desert lizards switching from sun to shade. So, homeotherms are usually but not always endothermic. These kind of phrases lend us to the thinking that poikilothermy is some kind of degenerate, undesirable, or primitive way of making a living.

Well, poikilothermy is primitive, in the fact that the first vertebrates were and are poikilothermic. Water is a heat sink. Because of its high specific heat, water tends to drain the heat out of surrounding objects. This makes sense, right? If not, go take the polar bear plunge in your winter clothes and read this again. So for fishes, this means that using your metabolism to keep warm would be very energetically expensive.

In that sense, poikilothermy represents an evolutionary advantage, rather than a disadvantage. Many fishes, such as tuna, actually have a physiological mechanism that enables them to be at least partially endothermic.

And very recently, scientists discovered the first fully endothermic fish. The Opah keeps its blood warm by constantly flapping its pectoral fins. This helps the Opah in the deep, cold waters of the Pacific where it lives. Tiger shark Galeocerdo cuvier swimming at surface with biologging package attached to dorsal fin. A white shark Carcharodon carcharias swimming at the surface with a biologging package attached to the dorsal fin. This package records temperature, swimming speed, depth, body movement and video footage.

Image shot by Andrew Fox. Like what we stand for? Share this on. Home News and Opinion Why are some fish warm-blooded? New study suggests it gives predatory sharks and fish a crucial speed advantage. OK Essential cookies.