Combining a electrocyte and a muscle fibre

Question

Basically the title itself. Is it possible to combine the function of a electrocyte and a myocyte, such that muscles double up as electric organs?

Electric organ

Myocyte

Observing the anatomy of a electric eel, we can see that they have specialized structures to generate electricity. These organs take up considerable volume in the body of the eel, and the electrocytes themselves are presumed to have evolved from myocytes. Therefore, to give a hypothetical supersoldier a electric attack ability, we could give them similar organs. While this is the easier option, it also comes with the downside of affecting the overall physiology of the metahuman, as a electric organ of sufficient power will require considerable space in the body. The other option is to modify the muscles and myocytes themselves. This is the harder approach, as it might require significant genetic and structural changes to the muscles, but the upside is that the muscular system is already available and present in every part of the body. Changes to it will not require a lot of physiological adjustment, and the sheer number of muscle groups available will mean an incredibly strong electric ability.

I have been thinking about ways to bridge the gap for a while, and it seems that the structure of a cylindrical battery comes closest to resolving the dilemma.

The layers of the "muscular battery" can be composed of a ring of muscle fibers arranged in concentric cylinders, separated by the endomysium. Upon neural activation, the myocytes in each alternate cylinder become positively or negatively charged, thus imparting a positive or negative charge to that layer/ring. The total voltage of that cylindrical layer is equal to the sum of voltages of each muscle fibre, and the sum of voltages of each layer is the output voltage of the muscular battery. It may be slowly discharged with low voltage, wherein only certain adjacent cylindrical layers are activated, for active electroreception , or it may be immediately discharged with large voltage, wherein every layer is simultaneously activated, for a electric shock.

However, I'm not a electrochemist or a biochemist, and I believe I lack the insight to decide whether this is practical or even possible. That's where you guys come in. I'm open to suggestions regarding my idea; whether it's possible, if I'm missing something critical or whether it's completely impractical and something else entirely might be a better solution. Any input is appreciated. Thanks!

Edit: Replaced the word 'circle' with 'cylinder', as that is a more descriptive word for the 3d model of a layer of muscle fibres, and added a bit more clarification.

Answer 1

The problem with making a dual-purpose muscle/electric organ is that muscles and electric organs perform their tasks in similar ways, but with very different structural minutiae.

Muscles work by combining a number of long, thin fibers in parallel, so that when they are stimulated, they shorten, pulling their ends closer together. By combining more fibers in parallel, the strength of the muscle can be increased, and by combining more in series, the distance over which the muscle can shorten can be increased.

Electric organs also work by combining a number of short, wide cells along their flat faces in series in order to increse the voltage that can be delivered. A single cell has a polarisation of around -70mV, and depolarises to around +30mV, for a total change in potential of around 100mV. In order to achieve the voltages achieved by electric eels, 600V+, at least 6000 electrocytes would have to be stacked in series, probably more given resistive losses. In order to increase the current, more cells would be stacked in parallel.

The first problem with a dual-purpose organ is that in order to reduce the current that passes through each unit area of an individual cell, it must be wide, and to pack more cells in and increase the total voltage output the cells need to be flat. This is in contrast to the needs of a muscle cell, which is long to increases the distance over which it can pull, and thin to increase duffusion of nutrients and wastes in and out.

The second problem is that muscle cells contract for long periods of time by combining stimuli/twitches that occur faster than the cell can completely contract and relax. Each twitch pulls the cell shorter and shorter until it cannot shorten any more. However, electric cells are used to produce singular pulses (even if they are close together), and if they are repeatedly stimulated faster than they can repolarise, their voltage output will drop. This is in contrast to the functioning of a muscle which becomes shorter with repeated rapid stimulation.

The third problem is that electrical stimulation of a cell such as a myocyte or electrocyte results in it firing just as if it was stimulated by nervous activity. This would mean that a hypothetical electromyocyte would self-stimulate, and that would result in an uncontrollable contraction. In effect, it would reduce the muscular capabilities of the animal while the electrical effect was active, because it would not be able to control both the combined organ's muscular action and electrical action as well as two separate organs could. In electric eels, there is a theory that the high-voltage organ is triggered by the activation of a medium-voltage organ, not directly by nerve cells, which would also be activated by the massive voltage difference. The medium-voltage organ probably acts as a mechanism to prevent inadvertent retriggering of the high-voltage organ.

So, while you could make an organ that would both contract and zap when stimulated, evolution will tend to favour whichever feature is more important and optimise the organ for that purpose. An organ that could perform both functions would be good at neither. It would be an intermediate stage in its evolution from one state to the other, whichever that might be.