Tachmut and Skrael

 

What is an inhospitable landscape to some may sometimes be comfortable to others, if they have the right adaptations. One of the most common critters throughout the Martian tundras is the tachmut, a type of lobostomian spirifer. Bodywise, this limbless space slug shows little difference from its relatives, except for a thin fringe of hair-like setae growing below the rim of the dorsal plates (the function of which is unknown). What sets it apart is instead its surreal grin. Atypically for most lobostomians, the arms of the tachmut are internally supported by rigid cartilaginous rods and have robust, molar-like teeth growing out of them, in structure similar to the teeth found in their verticutian cousins. The purpose of these is obvious. The main diet of the tachmut are the red filulithophores which carpet the whole tundra during summer. These are macroareonts, prokaryotic organisms that function like a mix of diatoms and dictyostelids. Almost all their above-ground organs, such as the stalk and the fruiting bodies, are protected by a chainmail of phytoliths, little armour plates made of silicon dioxide. Though this biosilicon shell is thin, it can cause heavy abrasion if consumed too much, which is why toothless herbivores like onychognaths largely avoid eating them. The tachmut can meanwhile fully exploit this food source, using its toothed corona just like how a horse’s jaw grinds down grass. Unlike a grazing mammal, the tachmut can continually replace its teeth once worn down. Once grinded into a pulp, the vegetation’s remains are whisked into the mouth using the characteristic setae.

Being the main consumer of this vegetation, the tachmut is a vital keystone of the tundra’s ecosystem. Filulithophores are major nitrogen fixers, but because few feed on them, the tachmut liberate this vital element and accumulate it in their bodies. Thus, the tachmut becomes an important source of nitrogen for all the predators and omnivores that feed on it. Perhaps more importantly, the gut of this space slug dissolves the ground up phytoliths into silicic acid. The nephridia (its equivalent of kidneys) then draw most water out of this substance, turning it into silica gel (which is why at least one Japanese desiccant company has made this alien their mascot), which is excreted out at the back with the other waste. This gel then dissolves in the wet soil of the boggy summer tundra, allowing filulithophores and various other flora and fauna to reuse the silicon dioxide for their skeletons.

Tachmut are classic r-type strategists when it comes to reproduction. Usually, when two individuals mate, both partners have their eggs fertilized. Like snails, they then lay these into wet burrows during the warmer summer months and slither away. Once the long winters signal their arrival, tachmut bury into the active layer of the permafrost while it is still malleable. Once settled, the organism enters a deep state of dormancy during which it is nearly dead and most of its body fluids are infused with a biologically produced anti-freeze, not unlike the red fronds it shares its environment with.

Some, however, make this season easier for themselves by exploiting their neighbours. Instead of digging their own, tachmut may simply crawl into abandoned burrows left behind by skrael. These are caecilian-like archaeocephalians. During the summer, these serpentine organisms build rather peculiar nests. First, they begin digging tunnels into the thawed topsoil of the permafrost, using their spade-like cranium, which has modified the head so much that the antennae grow from underneath the head. Then they actively suck up and spit out the excess water until the burrow is dry. To prevent the ground water from seeping in again, the nest is then plastered with a coat of sticky saliva that, like in some birds on Earth, quickly solidifies into a waterproof and isolating coating. The home is then further stuffed with fragments of sporian skin and the shed filaments of fuzzy animals that roam the tundra during the summer. From this cozy nest the skrael then lives a largely stationary life, using its antennae and skull to pick up the vibrations of any smaller critters crawling nearby its hole to snatch up the unsuspecting prey. The skrael’s eggs and young are also raised in these nests by the caring parent. During winter, the animals curl up into a ball and sleep, though at the same time they raise their metabolism, utilizing their body-warmth and the nest’s insulation to keep the interior above freezing.

Although the two animals usually do not seem to get along, an amusing observation that has been made by some researchers of the Martian tundra is that tachmut and skrael may sometimes be found enduring winter in the same hole. This likely does not happen out of friendship but out of desperation and/or apathy. The tachmut is desperate to find a winter home, while the skrael is too sleepy to be bothered by or even notice its new roommate. That said, it has been theorized that skrael may occasionally exploit this cohabitation by feeding on the dormant tachmut, should their own winter reserves run out.