We had barely discovered the Iberian lynx louse before it disappeared. The creature was first recognized in 1997 when an adult lice and a nymph (a baby lice) were removed from the skin of a dead lynx; he was later named Felicola isidoroi. At the time, Iberian lynx were in serious decline due to a virus in the rabbit, their prey. With this decline, the area of ​​the isidoroi is faded and its habitat is fragmented, lynx being less likely to cross.

When ecologists introduced Iberian lynx into captive breeding programs, they tamed them, destroying the natural environment that is a lynx. Even though the lynxes have not been sponged, it is possible that their lice did not survive the captivity. Wildcats in pens tend to over-feed and pace. These can be fatal for a louse that has been scratched or displaced by agitated movements.

A lynx probably does not cry his lice (they stung him!), So why should we care about lynx lice? In the end, we have good reason to pay attention to endangered lice. Some biologists argue that parasites and their hosts should be considered as a single entity because their interaction determines the evolution and health of both species. Their relationship can even make whole ecosystems more resilient. Perhaps, then, if we can not save all endangered species, we should focus on saving animals that harbor unique and rare collars, both on the skin and indoors. Several parasites have been shown to enhance immunity. Intestinal worms inside certain fishes absorb harmful heavy metals from their wearers' tissues. Some parasites have been called "green puppeteers" because of the way they alter the behavior of their hosts and alter the ecosystem. They encourage, for example, crickets to jump into watercourses, where insectivorous fish eventually flourish. or make the moose weaker, thus supporting the packs of wolves.

Parasites can also teach us about their hosts. Since lice evolve with their hosts, the genome of a specific louse is a record showing the history of its carrier species: the previous abundances of the large animal, its adaptations and its demographics. With the loss of the louse of the isidoroi, science has lost the means to explore the lynx's past.

Another lesson from the lynx and his louse is that the host does not have to go away for the creatures that underlie it to disappear. We are certain to have shared the world with other extinct, unmet and unobserved phenomena that have altered whole ecosystems. Each organism exists in relation to other organisms, and even the tiny, awkward and wiggling one deserves attention.

This article was published in the print edition of March 2019 with the title "A parasitic relationship".

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Rebecca Giggs is a writer from Perth, Australia. His work appeared in Granta and Good Medical Magazine.