Perchloraven

The toxic salt deserts of Mars are not home to many animals, most of them being small-to-microscopic extremophiles. But some creatures have learned to exploit the hostile landscape. In the northern hemisphere we have already encountered the caraxor, a flying pedicambulate which rules alone over the perchlorate wastes there.

In the wastes which pepper the highlands and tundra of the southern hemisphere can be found an organism roughly equivalent in ecology but highly aberrant in every other aspect, appearing like the Martian parody of a flamingo. The perchloraven is a member of the rare and elusive Monopoda, which are secondarily flightless ballousaurs. For whatever reason, their wings (former hindlegs) have atrophied. In some of the more archaic members they can still be used for gliding, whereas in more derived members like the perchloraven they can only be used anymore for social displays and balancing. This leaves only their single front-leg (formerly an arm) as an organ for locomotion.

This anatomy is obviously quite awkward and fragile, which makes it perhaps no wonder why these organisms are rare and only found in environments that lack competition or predators. The perchlorate deserts are obviously just such a place. Surrounded by kilometres of toxic plains and dust, the thermally heated brine pools which the perchloraven inhabits are isolated from the rest of Mars almost perfectly. Here it can awkwardly hop and shuffle around on its leg without fearing any danger.

Much like the caraxor, it can survive here thanks to a high resistance to saltwater and even perchlorate itself, having six nephridia (equivalent to kidneys) instead of the standard four that most other deltadactylians have, a genuine atavism it shares with more archaic onychognaths. Another surprising adaptation revealed by dissection is that the dark dots which colour its back and wings are actually caused by unicellular proteroareozoans which endosymbiotically live inside the organism’s skin. Highly infused with melanin, these microbes show signs of being radiotrophic, much like the fungi discovered in Chernobyl, being able to absorb and use cosmic rays and perhaps even ultraviolet radiation in order to metabolize. If this symbiosis simply exists to protect the perchloraven from the radiation it experiences at higher elevations or if it also gains energy from this relationship is not known. Some of these organisms can be found freely swimming inside the brine pools, so it is likely that the animal acquires them though its diet.

The perchloraven’s main method of feeding, filtering the briny water for small organisms, is evident by the long baleen-like bristles which grow out of its lower jaw, like the teeth of the bizarre pterosaur Pterodaustro. What the headcrest and attached skinflap are for is less obvious, though it likely serves as some form of social display. Perchloravens mate in pairs and give birth to live young raised in rocky nests. An advantage they have over their aerial cousins is that the loss of flight has made the pelvis much less rigid and narrow, allowing the chicks to be born much better developed. Usually they are able to stand, hop and feed by themselves a day or so after birth.

Why exactly the perchloraven is completely naked instead of having feather-scales like its relatives is a good question. Mainly living in thermally heated pools, it seems like there was no need anymore for insolation, allowing the organism to revert back to a more ectothermic metabolism in order to save energy.

On a zoogeographical note, it is also interesting that there is such a north-south divide between perchloraven and caraxor habitats. It has been proposed that the shrubland habitats which line the equator may prevent either organism from crossing into the other hemisphere, as they cannot feed in these zones and would also have to face predators which they have no natural defence against (Watzlawick 2114). What speaks against this is of course the fact that the caraxor can fly.

References:

• Watzlawick, Paul: Wide-scale niche partitioning across Mars, in: Journal of Xenobiology, 189, 2114, p. 310 – 377.