Luke

The luke (pronounced /luː/) are shapeless organisms that roam the corridors of Thorgh, helping to keep them clean of danger and debris. While lukes evidently serve a useful purpose for Thorgh, they can be dangerous to unwary travelers. They seldom come into well-settled areas, and are not too difficult to drive off with a concerted effort if they do, but those who run into lukes in less tenanted parts of Thorgh may find them a serious threat, as the lukes, in their voracious devouring of foreign matter, don't discriminate between inert refuse and living flesh.

The luke's name came about because it was thought to have some resemblance, both in appearance and in behavior, to the white blood cells of Terran gnathostomes, also known as leukocytes. The resemblance is not a particularly close one, but the name stuck.

Appearance

A luke appears like an amorphous white blob, with visible within its translucent outer membrane a stew of organs and other bodies, the most prominent of which is the yellow "nucleus". The nucleus is lumpy and wobbly, but otherwise more or less holds its roughly spherical shape. With their round yellow center within a white mass, lukes are sometimes said to resemble fried eggs, and in fact are sometimes colloquially called just that—or just "eggs" for short. Aside from the nucleus, the luke's gelatinous interior has a number of other features suspended in it, though the nucleus is by far the largest. The others are mostly visible as red and black specks, with the occasional larger ellipsoid.

Though it has no fixed shape and usually seems to puddle on the ground when not in motion, the luke can extrude pseudopodia when needed. It has little fine control over these pseudopodia, and certainly no manual dexterity, and cannot mimic a human hand; at best, a luke's pseudopod appears like a blunt club. Still, these are sufficient for it to attack with, to protrude to envelop food and draw it to its interior, and to move itself along by gripping the surface ahead with a sticky pseudopod and pulling the rest of its mass forward.

Lukes vary in size, but the largest can reach up to four or five meters in diameter when spread on the ground in a typical posture, and may weigh up to a metric ton.

Anatomy

While it may bear a superficial resemblance to an oversized single-celled organism, the luke is in reality, of course, no such thing. The "nucleus" of the luke corresponds to the nucleus of a cell in no way beyond its general appearance. On the contrary, the luke is a complex, multicellular creature, and even the apparently uniform gel or "protoplasm" of its interior is more complicated than it superficially appears.

Far from being an inert substrate, the protoplasm is in fact a soup of soft cells in constant relative motion. They pass between each other necessary nutrients and signals, acting collectively as a combined circulatory and peripheral nervous system. The "skin" that surrounds the protoplasm is in fact made of similar cells, though with slightly less cytoplasm within them and having attached to their neighbors. A protoplasm cell can quickly convert to a skin cell by transferring some of its fluid to other cells and then linking its cell membrane with other cells in the "skin"; a skin cell can likewise transform back to a protoplasm cell by dissolving the chemical bonds connecting it to the rest of the skin and receiving cytoplasm from neighboring cells. Precisely this is, in fact, precisely done when a luke ingests nutriment, forming a digestive cavity in its interior lined with new skin cells to hold its food. The skin cells also are somewhat sensitive to light and vibrations; their transmission of this information gives the luke a crude form of vision and hearing.

The other bodies inside the luke serve various purposes. The nucleus holds a large reserve of fat for the luke to live off of when food is short, as well as the closest thing it has to a brain. The gray ovals, called lysomers, contain digestive fluid, which is injected into digestive cavities to dissolve the luke's food into a form that can easily be absorbed by the skin cells. The other, smaller bodies in the protoplasm serve various secretory and regulatory functions the full details of which are still not understood.

Diet and behavior

Lukes are able to eat almost anything organic, containing lysomers filled with various different acids to break down different substances. Their only serious limitation is that they can only eat objects small enough for them to envelop, since they must take their food entirely into a digestive cavity to consume it. This is, perhaps, why Thorgh itself is apparently in no danger of getting damaged by the lukes. Its inhabitants, however, are another matter; humans (and many other noetic creatures) are certainly within the luke's size limits.

For the most part, a luke seems to do little but wander the ducts and organs of Thorgh, consuming anything organic that it happens across. Lukes usually (though not always) seem to avoid civilized areas, though it's unclear exactly why. It could be that Thorgh emits some chemical signal in such areas that keeps the lukes away, or it could simply be that they are deterred by all the sound and activity there... while they are certainly not averse to chasing down and devouring other fauna they come across, it could be that they instinctively want to keep away places where there are too many other creatures at once.

Reproduction

Though it's commonly assumed that lukes reproduce by fission, the process has never actually been observed, and many biologists believe it to be a myth. Rather, it seems that lukes don't actually reproduce on their own at all, but are directly created by Thorgh. Lukes are spawned off from Thorgh in locations called genesis pools, which can also generate other creatures native to Thorgh as well. Lukes seem to normally be spawned only one at a time in a given pool—necessarily, since otherwise the lukes would likely devour each other. Newly spawned lukes are relatively small, less than a meter in diameter, but they grow quickly to larger sizes as they scour their vicinities and consume more food.