I am thinking of writing a story about a Martian civilization. It might involve humans, but, I think it will be more interesting if there are creatures adapted to the Martian lifestyle as well. So, here is a proposed creature to live on Mars:
A burrowing reptilian, or so it seems. Photosynthesis is a tricky one. On the one hand, less light arrives at Mars than at Earth. On the other hand, the thin atmosphere means the light doesn't get as scattered. I decided that this creature would have photosynthetic skin, because it means the creature wouldn't have to worry as much about being sunburnt. When the creature is likely to be cold-blooded, that is important. Also, this can provide oxygen for the creature to survive since Mar's atmosphere is almost entirely carbon dioxide. I mean, yes, the creature would be more adapted to an anaerobic lifestyle, and when hibernating would probably go full on anaerobic, but, when active, it probably won't be fully anaerobic.
There are light sensors on top of its head, these connect to the part of the brain responsible for circadian rhythm. When they sense light, the creature wakes up. If they don't sense much light for a few hours, the creature goes back into its burrow to sleep. If after a day or two, there still isn't much light sensed, because, say, there is a global dust storm, the creature goes into hibernation. The Martian winter also forces the creature into hibernation but for a different reason. The Martian winter, even at the equator, is way down in the negatives. At night, it gets much colder still. An active creature during the Martian winter, if it isn't tiny, is going to freeze like an ice cube. Hibernation means that the little geothermal energy there is on Mars will be enough to prevent the creature from freezing to death in the winter.
As I mentioned already, this is a burrowing creature. It also is a nesting creature. This creature lays eggs during the spring, so that its offspring have plenty of time to prepare for hibernation. Because the chance of a global dust storm during any Martian year is 1/3, those that are unlucky to hatch during a year with a global dust storm will not survive, because they aren't well prepared enough. But, most hatchling deaths do not have to do with global dust storms happening at the wrong time. More are from lack of food, deformity, and predation than from global dust storms.
As the hatchlings grow, they rely less and less on aerobic metabolism. And the hatchlings start off tiny enough that photosynthesis can easily provide oxygen to all the cells, so oxygen storage isn't a huge concern for this creature. An oxygen storage system still develops though, while it is an embryo, just in case it has to flee or defend itself and thus needs extra oxygen that photosynthesis alone can't provide at a fast enough rate.
And this brings me nicely to the eggs themselves. When an adult eats another creature(yes, they go from complete autotrophs to a combination of an autotroph and a heterotroph as they grow and photosynthesis can't provide the full metabolic demands anymore), they inevitably will eat some iron oxide dust in the process. Instead of discarding all that iron in their waste products, in females, when they ovulate, some of the iron gets used to make egg shells. And because the egg shells are iron rich, they virtually blend in to the Martian landscape, which on the one hand, makes it much harder for predators to spot them without sensing infrared, but on the other hand, makes other burrowers more likely to damage the eggs, so the females will strategically place their nesting burrows to avoid this damage from other burrowers.
What do you think of my proposed Martian creature? Of course, there would be many more, but I can't ask about all of them. Is this a plausible creature to live on Mars?