Leukocrusts

Far left: C. albus calculus''. Tends to creep up rocks or the sides of a Burrowing Provuci; characterized by the relatively numerous, pebble-like specks of waste or ingested dirt on its surface. Upper left: C. albus cumulus. It is especially sensitive to UV light and moisture, and has a short lifespan among leukocrusts. Lower left: C. albus yumyum. Slow for a leukocrust, but it is remarkably persistent and voracious, with a huge mouth. Middle: C. albus vulgaris, the common leukocrust. Fairly large, and slightly light-blue. Smells like grapes when processed in a centrifuge.

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Genus Summary:

One crustling descendant became so successful as a predator of symbiocrusts that it diversified into a whole genus. This genus, the leukocrust genus, is characterized by the following traits: obligate carnivory, agility, use of malic acid to digest its prey, and a distinctive "train wreck" of the photosynthetic part of its genome. (one of the consequences of its wrecked photosynthetic machinery is the loss of green coloration for white coloration.)

Specific details:

Leukocrusts, by microscopic masses of congealed slime standards, is quite agile. The fastest known species/strain, Crusterusa albus celer, normally travels five times its body length in 24 hours, (up to 2.5 mm) but when very hungry, it triples its speed, and the distance traveled can be as high as 7.5 mm. (It does not sustain its top speed for the entire 24 hours. It may slow down or rest, seemingly at random)

Leukocrusts rely so heavily on eating symbiocrusts that they have no need for photosynthesis. Consequently, the photosynthesis genes accrued mutations over time, and eventually became an unusable wreck of incomplete chemicals. Unusable for photosynthesis, that is: a few parts of its photosynthetic genome were salvaged and re-appropriated for its carnivorous life. Malic acid, originally a part of its photosynthesis pathway, is now used as a digestive enzyme.

Leukocrusts hunt by creeping up to a colony of symbiocrusts, preferably a "peninsula" or "island" of the main colony, and then engulfing a few cells/pieces of the symbiocrust. In its "mouth", the prey is pumped full of malic acid, which is analogous to saliva, venom or stomach acids. The prey is broken down to its constituent proteins, which the leukocrust then absorbs. On the off chance the symbiocrust is not totally digestible, the indigestible waste is excreted to the leukocrust's surface. The waste almost always stays there, forming microscopic "pebbles" on the surface of the leukocrust.

While mostly microscopic, leukocrusts can grow to be as big as 0.5 mm because they have very little in the way of growth restriction in ideal conditions, as well as a surprisingly long maximum lifespan. In specific, it is Crusterusa albus gigans that may reach the size of 0.5 mm, and C. albus gigans also has the longest known lifespan of the members of the leukocrust genus, at five months. However, it's unclear how useful this is, since C. albus gigans is a colonial organism, and thus not exactly an individual organism. Therefore, it is better stated that the longest known lifepspan of a single leukocrust colony is five months.

The leukocrust usually reproduces by means of mitosis. Only in conditions of prolonged hunger or cellular stress do they produce spores. As cellular stress includes excessive UV exposure, it's expected that the leukocrust will increasingly rely on the spore option if Mason's ozone is not restored.