adaptations of deep-diving poikilotherms

.

Adaptation 1:

Many sorts of marine critters (fishes and reptiles and mammals) may have counter-current heat exchange systems.  Blood vessels flowing into the animal (bringing cold blood) are adjacent to blood vessels flowing out (with warm blood).  This helps warmth stay inside the body.


Adaptation 2:

Ok, this is really weird.

Swordfish have evolved a heater in an extraocular muscle which (with fat for insulation) can keep their eyes and brains 10-15 degrees Celsius warmer than the water in which they are swimming, the better to see prey and make decisions about catching it.

10-15 degrees (C)!!!  That's a lot!!!


Adaptation 3:

"Some deep-bodied fishes" (and he mentions tuna) can actually maintain their core temp at a temp above the water in which they are swimming.  Ergo, they are endothermic, at least to some degree.

!!!


Adaptation set 4:

Leatherback turtles are big, active, and have counter-current heat exchange and good fat stores (think "blubber").  They can maintain their body temp at 18 degrees (C) above the water in which they are swimming. 

Another critter formerly known as "cold-blooded" that sounds to me like it's pretty darn homeothermic (to use the term which has apparently replaced the notion we used to think of as "warm-blooded").............




Who knew?

So many things I learned as black and white when I was a kid are turning out to have a lot more shades of gray than we used to think!

.