Within the vast universe that Gene Roddenberry devised for his legendary Star Trek series, there are a large number of creatures with amazing biological traits. On the planet Janus IV, the officers of the Enterprise in the original series discover the ‘horta’, a life form based on silicon. In Star Trek Discovery, Ripper is introduced, a specimen of a species of extraplanetary giant tardigrade capable of feeding on a no less peculiar fungus, Prototaxites stellaviatori —which cannot but remind us of the very strange fossil fungus of the same name—. Also noteworthy are the Cardassian rats from Deep Space Station 9, the Alpha 177 dog —which is nothing more than a small dog with a horn on its head— or the sehlat , Vulcan’s own animals, which were domesticated by the popular aliens with green blood and implacable logic.
But apart from humanoid species with more or less developed technological societies, probably the most popular creatures in the Star Trek universe are the tribbles , with the fictitious scientific name Polygeminus rex (although they are also called Tribleustes ventricosus ), small oval creatures, completely covered in fur, who first appeared in the original series episode ‘The Trouble with Tribbles’.
The voracity of a plague
One of the first details we learn about tribbles is their voracity . Although they lack teeth, and do not pose a direct danger to people, they devour any food that is within their reach. A single tribble can eat the equivalent of its weight per day.
This behavior exists in the real world, in some insect species such as the desert locust Schistocerca gregaria . These animals are normally solitary, but at a given moment, when conditions are favourable, they can form swarms that become the most threatening pests for agriculture in the world .
Another characteristic feature of tribbles is their great reproductive capacity. According to Doctor ‘Bones’ McCoy, up to 50 % of tribble metabolism is dedicated to reproduction . The very short life cycle – it produces a new generation in just 12 hours – generates frequent large demographic explosions , in which the population, if it had enough resources, would grow exponentially.
This behavior, although not so exaggerated, is also observed in real life with some animals. Lemmings , rodents that share similarities with tribbles—and on which they are probably based—have very short reproductive cycles and high fertility, causing these types of population explosions to occur cyclically.
In the case of these famous rodents, predators sustain populations, and when they are too numerous, it is the very carrying capacity of the ecosystem – that is, the maximum amount of available resources – that limits the growth of populations, generating after every population explosion an event of high mortality. It is logical to think that something similar would happen on the planet of the tribbles; in fact, the series raises the existence of some reptilian organisms that would act as natural predators of the tribbles, controlling their populations.
But going back to the lemmings for a moment, the event known as “ lemmings mass suicide ” is well known, which is more myth than reality. The idea that lemmings engage in such behavior became so popular in the literature that many took this finding for granted. However, studies of the biology of lemmings suggest that they do not jump off cliffs or engage in other group behaviors that lead to intentional or unintentional death.
What’s more, the behavior has not even been observed by reliable sources; the only record available is in the documentary White Wilderness , produced by Disney in 1956, shot in a place where lemmings do not live. The animals had apparently been captured, transported there, dumped from a truck at the edge of the cliff, and then pushed to jump.
Tribble mothers: newborn and pregnant
Going back to the biology of the lovable aliens from Star Trek, the enormous reproductive rate of tribbles actually lies in an even more peculiar biological trait. All tribbles are female and are born pregnant . They reproduce by apomictic parthenogenesis. In this process, the germ cells, by simple mitosis, divide to give rise to new embryos, which are clones of the mother. In this way, a single female produces up to 10 offspring in a litter, each with new embryos already gestating inside.
We find this same behavior —although with longer time periods— in several species of aphids . During part of their life cycle, female aphids bear viviparous offspring in the form of new female aphids; they take about a week to have a new litter, made up of between 50 and 100 new pups, which, as has been indicated, are often born pregnant .
The tribble as a pet
In the episode of the original series, the first tribble arrives on the Enterprise from Lieutenant Uhura (played by Nichelle Nichols ), who buys it at a supply station, convinced by its seller, because it is cute and adorable, and emits a soothing murmur, like a purr. The officer was unaware of the potential of this species, and finally ends up causing the serious problem of overpopulation in the ship that we see in the series.
But it’s not the only disaster caused by tribbles in Star Trek. In the Klingon Empire, they are considered a major ecological threat . These animals arrived on the planets of the Empire accidentally transported by the ships, and colonized several planets. The Klingons attempted to eradicate tribbles from the galaxy, even creating a genetically engineered creature specifically designed to hunt tribbles—to no avail.
The entry of exotic species that do not belong to an ecosystem is a very real threat. In the analogy of tribbles we can find many exotic species that, either because they have been accidentally transported on ships or planes, or because they have been introduced as ‘cute and adorable’ pets, end up causing real ecological disasters. In fact, just like the tribbles on Kronos, invasive species are currently the biggest threat to biodiversity in our real world.
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Davey, P. M. 1954. Quantities of Food eaten by the Desert Locust, Schistocerca gregaria (Forsk.), in Relation to Growth. Bulletin of Entomological Research, 45(3), 539-551. DOI: 10.1017/S0007485300029618
Johnson, R. J. 2018. Finding the truth: blind faith and the lemming phenomenon. Journal of the Royal Society of Medicine, 111(5), 175-176. DOI: 10.1177/0141076818766730
Moran, N. A. 1992. The Evolution of Aphid Life Cycles. Annual Review of Entomology, 37, 321-348.