I have an alien species that is my pet project. Now I'm to reproduction, which I have a specific idea for, I'm just not sure exactly how it works. My creatures are aquatic, and everything goes on underwater.

The female lays eggs, which are probably about the size and shape of a golfball. The male fertilizes them soon after, then coats the eggs in his saliva. These creatures then need to grow, still inside the egg, to a football shaped thing about a foot long, at which point they will emerge from their eggs. The areas these eggs are laid in are nearly stagnant pools of freshwater, such as lake bottoms, swamps, bayous, deltas, meres, or ponds. You get the idea. Probably.

These creatures are capable of producing electrical signals, using them for hunting, visualizing their surroundings, and possible for communication. So during the later egg development small aquatic creatures could potentially be lured in using electrical signals. If that helps at all.

These creatures are humanoid, and are on average about 4.5-5 feet tall. You can assume their dietary needs are about that an electric eel, only scaled up.

The main issues I see are the actual egg, which I assume would have to be some kind of membrane capable of growing. I was thinking of having the male's saliva help digest nutrients, which would then be absorbed by the membrane, feeding it and the creature within.

The question is, is this feasible from a biological standpoint? If not, how can I make it more so?

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    $\begingroup$ I based these things off of a lot of different animals; humans, electric eels, salmon, cyclops, and octopi. They're my pet monstrosities. $\endgroup$ Mar 6, 2016 at 4:25

2 Answers 2


You could have the initial egg being a thick hard shell (lets say some predators would be not able to digest it at that stage, like it works for some seeds). While the alien grows the shell softens and becomes more and more elastic, the wall gets thinner while the alien growing inside pushes and stretches it. You could have the saliva coating as system to start the whole process, lets say that for whatever reason the fertilized egg remains in a stasis until coated (make it a sort of embryonic diapause, some deer use that for example, lets say that laying and fertilizing the eggs is a vulnerable phase for the adults because of certain predators and the male coats the egg with saliva only when is safe for the eggs to develop). A membrane that is more or less elastic wont need to grow it would just get thinner and thinner, like a balloon.

You have a list of animals that inspired you, I think that if you include some plants you can find some strategies that will allow you to get around some problems.

In the comments you raised the problem of nutrition. It could be solved in various way, your choice which to choose. But you can also mix all of them: the egg development could have various stages using a different nutrition strategy for each. You could make that for the first phase there are enough nutrients already in the egg, that can be justified as a system for the initial survival of the egg in an hostile environment, then for the other phases the thinner the membrane becomes the more permeable it gets to external nutrients. As you allow luring of small prey then that could get "stuck" to the egg membrane where some enzymes reduce it to something that can be absorbed in the egg, the enzymes themselves could be the sticky substance that holds the prey, a bit of carnivorous plant as inspiration. Or if electrical signals can be strong enough to zap a small prey decomposition can be enough to make nutrients available in the water surrounding the egg.

Also the alien inside could promote a degradation of the membrane into whatever nutrient you decide them to use (some intracellular parasites induce proteasomal degradation in their host to obtain nutrition). This degradation could contribute to the egg membrane permeability, increase of elasticity or just as a final stage where the degradation phase ends making the elastic but tough membrane fragile enough to permit hatching... all of them or just some of them or just one solution, pick and choose, its your choice how you want to spin it.

  • $\begingroup$ Good idea, and nice answer, although I'm still unsure if the egg would be able to draw in enough nutrients to do all of that growing, after all, embryonic sacs only get you so far. Also, aren't deer mammals, not egg layers? Also, I'm pretty sure I didn't include any plants in my list. $\endgroup$ Mar 6, 2016 at 5:02
  • $\begingroup$ Yes embryonic diapause would refer to a mammal, thats why i said sort of, i dont see why you cant use a similar principle for an egg, after all a seed that will need stratification etc uses the same idea, just fill the space and include the egg. You can place enough nutrients within the egg, how much there is and how much is needed can be your choice, the membrane could degrade too overtime releasing nutrients or letting some nutrients from the environment pass through, get inspiration from a cell wall for that. You can also get inspiration from how intracellular parasites work. $\endgroup$ Mar 6, 2016 at 5:11
  • $\begingroup$ That explains why you said deer, although still no plants. So you are suggesting that the eggs could contain some nutrients for that growth, and/or draw in nutrients from the eviornment, and possibly packing the eggs in edible or nutritional substances? Sounds interesting, and seems like a pretty good idea. Maybe you could elaborate in your answer a little bit. $\endgroup$ Mar 6, 2016 at 5:16
  • $\begingroup$ I edited it a bit $\endgroup$ Mar 6, 2016 at 5:30
  • $\begingroup$ I quite like it $\endgroup$ Mar 6, 2016 at 14:40

I think that the nutrition problem that you raised is the big deal. An egg can only contain a unchanging amount of nutriments. I can see only two ways of dealing with the problem :

  • The egg "filters" the water

The egg of your creature could filter the water, pre-digesting the small organisms passing by, transforming them into nutriments for the cute little alien baby. The egg would have to be layed in a place where the flow of water is enough to sustain the alien baby.

  • A larval stage

The phenomenom of metamorphosis is pretty well known. Everybody knows about the butterfly metamorphosis. To quote Wikipedia on Metamorphosis :

Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some insects, fishes, amphibians, mollusks, crustaceans, cnidarians, echinoderms and tunicates undergo metamorphosis, which is often accompanied by a change of nutrition source or behavior.

Some fishes undergo metamorphosis (you shoud look up Ichthyoplankton). That means that you do not have to restrain yourself to the egg. The alien baby could continue to grow as a larvae. Moreover, you could imagine that the larvae creating a new "egg", a shell. This new shell would become bigger and bigger each time the larvae would create it. This could be a life cycle with multiple larval stages and metamorphosis.

(As a side note, this is my first answer on the website. I've been creeping in the dark for too long and now, I want to express myself :-) )

I hope my answer will help you.

  • $\begingroup$ Nice first answer, I think this addresses my question nicely. The nutrients aspect of it was what concerned me as well. $\endgroup$ Mar 16, 2016 at 3:35

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