The opah, or moonfish, a large colourful fish living across the world's oceans, has been found to have a warm heart and maintain a high body temperature, according to a report in the journal Science. It's a zoological curiosity and a remarkable evolutionary development for fish.
In the cold darkness of the deep sea there is a clear advantage to being warm-blooded and able to move faster than all the other creatures in order to hunt them down or to avoid being eaten. Mammals such as seals or whales exploit this to great effect. They take a big breath and dive down, insulated from the cold by a thick layer of blubber, to snatch live food such as squids, fish and shrimps from the depths.
Until now it was thought that fish couldn't keep warm in this way because instead of breathing air they extract oxygen directly from the water through their gills.
Read more (The New Zealand Herald - nzherald.co.nz) ...