Wadjets

Wadjets are the flying members of the larger phylum Aspiderma (which also includes aquatic relatives and limbless worm-like varieties). They are best described as Mars’ closest analogy to the flying insects of Earth. Like them, they are completely covered in an exoskeleton and fly with outgrowths of said skeleton. That is largely where similarities stop.

The cuticle and exoskeleton of wadjets is for example not made of chitin, as in arthropods, but instead of a material called tunicine, which is also used by a variety of other Martian organisms, such as the Antitremata or the chirorbites and other fractarians. Tunicine may sound like an exotic material, but is simply a more specific descriptor for cellulose when it is produced by animals instead of plants. On Earth, tunicates are the only animals that make use of cellulose, hence the name, while on Mars it is a quite common building material for the fauna. This seems strange at first, seeing as how chitin and cellulose are very similar polysaccharids, though the devil is always in the detail. Unlike cellulose, chitin requires nitrogen for its production, of which Mars is naturally starved of. This makes it clear why tunicine has replaced chitin on this world.

The wadjets’ head structure is also rather unusual, as can be seen in the above illustration of the Sirek. It consists of an often elongated segment made up of various hardened plates, resembling somewhat the head shields of prehistoric agnathan fish. Most striking is the main eye plate which in most species points straight forward above the mandibular jaws, almost like a pair of goggles. On top of the head are more eyes facing up, possibly to detect flying predators or changes in light and weather. Instead of tracheas, wadjets breathe through gill-slits embedded in the ventral skull-plates, which lead to complex book-lungs. The jaws of wadjets consist of two or more mandibles right beneath the main eyes, which open horizontally in some species, vertically in others. The six  to eight beady eyes of the wadjets are not compound eyes, but primitive, liquid-filled lens-eyes, not unlike those of you and me (though instead of having eyelids they are just covered by a thin translucent sheath of the exoskeleton). The only other group of organisms on Mars that evolved similar eyes are the chirorbites. Behind the head-piece begin the wings, which usually number six to eight, except in the aeropedes. At the end lies the so-called “telescon”, on which I shall comment later below.

Most wadjets are aerial predators that have adapted towards hunting other wadjets and the flying nymphs of shellubim, as seen here with the Athlit. This species even evolved a sort of “nosehorn” for this purpose, which it uses to disorient and stun flying prey, much as a marlin does with fish. Larger species of wadjet also prey on ballousaur onychognaths and even smaller members of the flying tripod periostracans. There are of course also non-predaceous members. Most of those feed on the sap of softer fractarian flora with specialized mandibles which can cut through the cuticle and suck the organism dry. Unsurprisingly, some groups descending from these herbivores have come to utilize their mouthparts to parasitically feed on larger animals. A few gnawing wadjets have also been reported, which burrow into the trunks of spongisporians much like worms into an apple.

Though wadjets are found in nearly all regions of Mars, the reproduction of most is heavily tied to the spring thaw in the southern and northern tundras. As the permafrost does not allow it to trickle away, the meltwater accumulates into shallow, stagnant bogs and ponds into which the masses of migrating wadjets lay their eggs. Their young begin life as worm-like aquatic nymphs, similar to more primitive aspiderms found at the poles and underground, which gradually grow their wings out of what appear to be external gills at the back. At the height of spring, these fly out of the water and feast on the abundant shellubim nypmhs, the revitalised vegetation and various migrating animals around before following their parents back home once winter freezes the tundra again. Many wadjets have however completely lost their ties to the water and give live birth to fully developed young, sometimes mid-air.

What is peculiar about wadjets is the complete lack of walking limbs, allowing for only cumbersome locomotion on the ground. Some signs point towards this being a legacy of a rather peculiar origin story. Evidence exists that when Mars had oceans it also had a much thicker atmosphere, constantly resupplied by volcanic activity and possibly with average air pressures almost twice as much as on current day Earth (Hu et al. 2015). Combined with the low gravity, this would have made flying feel more like swimming. Various signs from the fossil record point towards the wadjets descending from a marine aspiderm ancestor that, in such a more benevolent atmosphere, evolved flight directly instead of first going through a walking terrestrial stage. Perhaps the wadjets first used their wings (likely derived gills as in their nymphs) to sail across the water’s surface, before learning to glide short distances to avoid predators until eventually gaining fully powered flight. From that point on, wadjets seem to have lived an almost completely aerial life swimming through the atmosphere almost without ever having to touch the ground. This, as microfossils indicate, they did together with a variety of smaller lifeforms that must have formed huge clouds of aeroplankton. This extinct aeroplankton must have bee much more extensive than the poor excuse that exists today on Mars and likely played an ecological role much more like actual marine plankton. Attesting to this is Regnopteryx gigas the fossil of a giant wadjet from eons ago, whose giant, cuticle-enforced wings must have reached larger spans than what was seen in any of Earth’s pterosaurs (Sivgin 2345). It had a unique filtering mouth structure not seen anymore in modern wadjets, which strongly suggests this creature lived like an “air-whale” by feeding on the abundant aeroplankton of prehistoric Mars.

The days of the air whales are long gone. Though the low gravity still assists, the loss of much of Mars’ atmosphere has made flight much harder. The wadjets, with their now cumbersomely heavy exoskeleton, had to reduce much in size to stay airborne and also had to find ways to be more adept on the ground. For this purpose, it seems, they have evolved a telescon, which is not found in most fossil members, who had a simple telson or pygidium. The telescon is a series of tail-segments nested into each other which the wadjet can extend or retract like a floppy telescope. With this extendable tail they can more easily slither on the ground, as demonstrated here by the King Discouraeus. It is what has earned these animals their name, for the deity Wadjet was long depicted by the Egyptians as a winged serpent.

References:

• Hu, Renyu; Kass, David, Ehlmann, Bethany; Yung, Yuk: Tracing the fate of carbon and the atmospheric evolution of Mars, in: Nature Communications, 6, 2015.
• Sivgin, T.K.: Life on a Dead Planet. The first 3 billion years of Evolution on Mars, Zürich 2345.