The “koopa” turtles of the Mushroom Kingdom are highly social compared to others of their order. The descendants of the troopa were nomadic grazers, and this began selecting for herding behavior. Today you will often find huge herds or “troops” of wild koopa. These troops are surprisingly cosmopolitan, with species from different genera travelling and working together for mutual benefit. Mixed herds are not uncommon in nature, it has been observed in dolphins, primates and herd mammals. In areas abundant in food, cooperation between species allows them to work together to spot predators without risking losing that food to another species. As many of the contemporary koopa species are sapient, we can see how genetic evolution effected cultural evolution and vice versa. As evolutionary changes made cooperation beneficial, it selected cultural traits that encouraged cooperation. At the same time, these cultural factors selected for species with biological differences that would be suited for each other. Today there are many examples of intriguing symbiosis and co-evolution within the mixed koopa troops.
Diagram of internal workings of Oesovaribilis piras
A. Explosion chamber as well as glands which produce special catalyst enzymes
B. Storage tank
C. Glands which produce hydrogen peroxide
One member of the “upright koopa” genus of Oesovaribilis evolved a peculiar trait that would lead to huge genetic and cultural changes for the koopas. The aptly named Fire Brother (Oesovaribilis piras) is able to produce a “ball” of chemical fire and project it out from its mouth with such velocity that it skips across the ground. This chemical reaction is possible thanks to a system of specialized organs within the turtle, similar to that of a bombardier beetle. A specialized organ produces the chemicals needed for this reaction, and a storage organ keeps them separate until needed. The chemicals are heated internally to around 100 degrees Celcius (212 degrees Fahrenheint). When the turtle is confronted by a predator, the chemicals are released from their chambers and mix in the blasting chamber, causing a violent chemical explosion that propells the fireball out of its mouth. The lining of these organs and the turtle’s throat is extremely resistant to burns, protecting it from misfires.
Such a dramatic evolutionary change is the result of exaptation. Essentially, a trait develops for one purpose and then, as it proves useful in another circumstance, evolves further to exploit this new niche. This can lead to seemingly rapid and dramatic changes. A classic example of exaptation is how feathers originally evolved to help regulate heat, were then adapted for display and sex selection, and then were once more adapted for flight. The ancestors of the Fire Brother may have adapted these chemical chambers for another purpose (such as heat regulation or as a by-product of digestion) and then later as it became useful for protection it adapted to better exploit this trait.
Skeletal workings of Acutagaster canescans
Whatever the origin, this dramatic adaption caused the ancestors of the contemporary Fire Brother to split off from Oesovaribilis and create two new genera: Acutagaster and Piragaster. The Acutagaster genus is better known to most Mario players as “Spikes”. These turtles have an atrophied shell, almost useless for defense, but the expanded and elastic ribs allow the Spike a great degree of internal flexibility. Unlike their ancestors, the chemical reaction within them is not volatile. Their internal chemical chambers exit into the stomach and combine to create large calcium growths resembling large, spiked balls. The Spike can regurgitate these “spiked balls” out of their frog-like mouths and into their hands to hurl them at predators. The strong, elastic internal lining that protected the ancestors of the Fire Brother from burns have adapted to protect the Spike from puncturing itself with these calcium growths. Some species of Spike are even able to produce a single spiked ball nearly the size of its own body. Their elastic inner lining carefully shifts and maneuvers its internal organs around the growing spiked ball, protecting them from being crushed. This is similar to how the kiwi bird of New Zealand can lay an egg the size of its body without crushing itself to death.
Various Piragaster species. Note the extravagent coloration and “hair”
As fascinating as the Spike is, the Piragaster genus may win the prize for being the most radically changed species of turtle found in the Mushroom Kingdom. Like its ancestors, the Piragaster is able to produce a volatile chemical fire from its internal organs, but these species are also able to produce continuous clouds of flaming chemicals in addition to the focused bursts of their kin. Like Acutagaster, they grow long, colorful, hair-like fibers from their heads and faces. This most likely arose as a form of sex selection. While Acutagaster “hair” tends to follow specific patterns, the various Piragaster species have elaborately colored and shaped coifs, much like the feathers of birds of paradise. Their shells have become equally colorful and may be decorated with a manner of spiny growths. In a development quite different from the other descendents of Terrapene fungus, the shells of the Piragaster genus are still quite large and useful for defense. While they have lost some of the mobility of their relatives, the Piragaster have also developed large frames and extremely powerful muscles allowing them to move quite quickly on land despite their heavy, rigid shell. Some have powerful leg muscles allowing them to leap or dash forward suddenly. Unlike their relatives, the Piragaster appears to be omnivorous and has sharp teeth for tearing flesh. These are not true teeth, but rather sharp spikes of bone that are part of the skulls (as seen the skeletal reconstruction below). The largest species, Piragaster rex, has sharp “teeth” as long as a Mario’s hand.
Skeletal reconstruction of Piragaster rex
This physical strength may be part of the reason that Piragaster genus tend to be the dominate species in mixed troops of koopas. Nearly all communities are ruled by a mature Piragaster rex “monarch”. But the reason for this is not simply physical might or genetic determinism. The current civilization of the koopa is the result of years and years of cultural adaption and evolution. However, that topic will have to wait for The Anthropology of the Mushroom Kingdom. Next time we continue plumbing the warp pipes of evolution with our analysis of the Yoshi.