Creatures Caves

I'll just speculate here.

For a norn to be able to survive without a heart, his body's cells would need to be able to produce ATP in the absence of oxygen. This is because without a heart, the oxygen drawn into the lungs would go nowhere - there's no circulation, so it can't get distributed to other body cells. Of course, in order to produce ATP under these circumstances, his mitochondria would need to be able to perform a full glycolysis reaction with no oxygen involved.

Here are the steps (and genes within each step) of glycolytic ATP production in a normal norn:

1. [0076] Fatty acid to pyruvate
[0079] Glucose to puruvate
2. [0081] Pyruvate to energy <--- NEEDS OXYGEN
3. [0086] Energy to ATP.

Here are the involved genes' derived chemical formulas in detail:

[0076] - 1FattyAcid+6ADP --> 8Pyruvate+6ATP

[0079] - 1Glucose+2ADP --> 2Pyruvate+2ATP

[0081] - 1Pyruvate+3Oxygen --> 6Energy+3CO2(diss.)

[0086] - 1Energy+6ADP --> 6ATP

While both genes within step 1 produce ATP as a product, that ATP is used up as energy within the glycolysis reaction as a whole, and so it does not escape the system.

The ATP which escapes the system to be used in other areas of the body is that which is produced in the last step - but only after the introduction of oxygen at gene no. [0081].

I suspect that a mutation on this gene - a mutation which, perhaps, replaces "oxygen" with either "nothing" or some other naturally abundant chemical - would allow a creature to be able to bypass the need for oxygen in glycolysis as a whole, and thus to produce ATP without the need for oxygen transmission in the bloodstream and, it follows, without the need for a heartbeat.

... However, this only explains how he'd be able to survive without a heartbeat, not WHY he doesn't have one in the first place.

As to that conundrum... I would further speculate that something has targeted the heart muscle specifically and caused it to die - cyanide can do just that. And so, perhaps this norn has a combination of the aforementioned genetic mutation and a second mutation which causes him to produce toxic amounts of cyanide? Maybe a mutated emitter gene?
That would seem to be able to cause the heart muscle specifically to die whilst still preserving normal ATP production and thus upholding the function of all other muscles and systems in the body.

But like i said, it's just food for thought. ^w^