"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift

June 10, 2024

Forficuloecus pezopori

Parasites are a major part of biodiversity, but they spend most of their time hidden in plain sight. Even with some animals that have been known to science for centuries, their parasite fauna remains completely unknown. This can either be due to the lack of research interest into their parasites, or the host animal is just really rare, so there has been very little to no opportunities to study the parasites that live on or in them. In some cases, those rare animals are at risk of going extinct, which means their parasites and symbionts may also disappear before we even know they exist. This post is a story about a ground parrot and its hidden louse.

Left: Forficuloecus pezopori louse viewed under light microscope, Right: a western ground parrot (Pezoporus flaviventris).
Both photos from graphical abstract of the paper

The parasite being featured in this post is Forficuloecus pezopori, and it is the first known parasite from the western ground parrot (Pezoporus flaviventris), also known as Kyloring. Kyloring is one of the rarest parrots in the world and is considered critically endangered, which is bad news for F. pezopori, because we have barely gotten to know this little insect, and it may already be at risk of disappearing along with its feathered host. Lice are particularly vulnerable to co-extinction as they are completely helpless off the host's body and are often specifically adapted to living on just one particular host species.

Forficuloecus pezopori was found on some captive ground parrots at Perth Zoo, the lice were hanging around the feathers at the back of the birds' head and nape. As far we know, the western ground parrot is the only host for this parasite. There is a slim chance that it might also be found on the western ground parrot's closest relative, the eastern ground parrot (Pezoporus wallicus), but we can't verify that at this point, because we know so little about the parasites of ground parrots in Australia.

For example, a subspecies of eastern ground parrot in Tasmania was found to support a type of feather mite called Dubininia pezopori but it is uncertain whether that mite is unique to just that particular subspecies, or if it is also found on the mainland eastern ground parrots, since nothing is actually known about the parasites and symbionts of those birds. Given the eastern and western ground parrot have been separated since the Pleistocene about 2 million years ago, there would have been enough separation in time and space for the two species to develop their own distinct collection of parasites. So as far as we can tell, the Kyloring is the only host for F. pezopori.

Parasites on endangered hosts such as the Kyloring are in a precarious position, because not only are they at risk of dying out alongside their hosts, historically, there have been cases of parasites being wiped out in the process of people trying to conserve their hosts. For example, during the California condor breeding program, a unique species of condor louse was wiped out due to the pesticide-based delousing that the birds received when they were taken into captivity. And the California condor louse is not the only victim of extinction via conservation efforts. The Iberian lynx louse also suffered the same fate

Even more tragic is the case of Rallicola extinctus - a louse of the Huia, which was a species of New Zealand bird that became extinct early in the 20th century, with its last confirmed sighting in 1907. But the louse that it hosted was not even formally described until 1990 - many decades after the host had already gone extinct, hence the species name R. extinctus. Forficuloecus pezopori and many other lice species are at risk of such entangled fates, or become victims of well-meaning conservation efforts.

While a lot of people may not mourn the loss of parasites, it might be their hosts that end up missing them the most. The presence of parasites may help them develop a properly functioning immune system, and their absence could leave the host with a range of physiological disorders. And these parasites might be better off together with their hosts as they can tell us a lot about how the host animals live, and the ecosystem they exist in.

To rectify the mistakes of the past, the researchers suggested that any future studies on wild populations of ground parrots should incorporate a routine louse check to see how common F. pezopori are among those birds, but not to remove any of the lice that are found, and just let those little insects be. Especially since they don't seem to harm healthy, wild parrots. At the same time, lice infection on captive birds can serve as an opportunity to learn more about F. pezopori - saving the host along with its parasites at the same time

Living organisms are intertwined within a network of ecological interactions, if you pull on one loose thread you might trigger a series of co-extinctions and unravel the entire tapestry. Because of those connections, we could be losing more species than we realise.  Though they are often hidden out of sight, and thus out of minds, losing parasites and symbionts would leave us with emptier ecosystems and a lesser world.