"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

January 17, 2020

Ceratophyllus (Emmareus) fionnus

When it comes to conservation and protecting threatened species, fleas would not usually be high on most people's list. Not only because most people are not fans of parasites, but also insects and just invertebrates in general gets little attention compared with charismatic megafauna, which attracts far more conservation resources. Additionally, there are comparatively less scientific research being conducted on invertebrates compared with vertebrate animals. So less is known about them, despite 99% of all animal life on Earth being invertebrates, and at least one fifth of them are under threat from extinction.
Adult Ceratophyllus (Emmareus) fionnus [insert: a Manx shearwater in flight]
Photos from Fig. 1 and 2 of the paper
Which brings us to the topic of the paper we are discussing in this post - a flea. But we're not just talking about any flea, we're talking about Ceratophyllus (Emmareus) fionnus which parasitises the Manx Shearwater (Puffinus puffinus). Like many other birds the Manx Shearwater is host to a wide range of parasites, both external and internal, but what makes C. (E.) fionnus special is that even though the Manx shearwater has a wide distribution across both the north and southern Atlantic ocean, this little flea seems to be found exclusively on an island off the coast of Scotland called the Isle of Rùm - and nowhere else. This alone earns it the distinction of being one of the few species of endemic Scottish insects.

The life cycle of fleas involves a non-parasitic larval stage that feeds on organic detritus in the surrounding environment. Only when the worm-shape larva pupates and emerges as an adult does it begin its vampiric life style. The Manx shearwater spend most of its life out at sea and only visits the Isle of Rùm to breed, and based on the life cycle of other seabird fleasC (E.) fionnus would breed in the nest and bedding. So when their hosts leave, the fleas stay and overwinter as pupal cocoons near the nests, and when spring comes, the blood-hungry adults emerge, eagerly awaiting the return of their hosts. While this arrangement seems to have worked well for C. (E) fionus, being restricted to a single island also makes it rather vulnerable to becoming extinct due to environmental changes.

There have been other cases of bird ectoparasites which have gone extinct in the relatively recent past due to various different reasons. The Huia louse, which only lived on the New Zealand bird Huia, is thought to have become extinct along with its host in early 20th century. And then there was the Californian condor louse - a species which was ironically (and unnecessarily) rendered extinct in an effort to conserve another (its host) during the Californian condor breeding program.

Those are just the cases that are better known - it can be safely assumed that throughout recent history, the extinction of many bird species around the world have been accompanied by an unnoticed wave of parasite co-extinctions. So how would one go about coming up a plan for conserving a species of flea? In a recently published paper, a group of researchers outlined a potential roadmap for protecting C. (E.) fionnus.

Like most invertebrates, there isn't much information on some of the most basic aspects of C. (E.) fionnus' biology, including their distribution and population level, so to start out with, we need to learn more about this flea species. But the usual methods for sampling and identifying insects and parasites will not be suitable since they often result in the death of the animal in question. So the researchers suggested that surveys of C. (E.) fionnus should use non-lethal methods for immobilising the fleas such chilling or carbon dioxide so that they can be identified using a field microscope.

While the Manx shearwater colony has been fairly stable on the Isle of Rùm, in more recent times their nest have come attack from introduced brown rats - and obviously if the shearwater colony disappear from the island, so will C. (E.) fionnus. So what can be done to safeguard a viable population of a flea species? Unlike other threatened animal species, captive breeding is not really an option for C. (E.) fionnus - raising a parasite species in captivity implicitly involves keeping its hosts in captivity and when the host in question is a migratory seabird, that's out of the question.

So the researchers suggested creating "insurance" populations of C. (E.) fionnus on some of the other Manx shearwater colonies within the British Isles. They nominated six potential sites to translocate founding populations. Translocation is a common strategy for conservation of vulnerable or endangered species. But this hasn't really been done before for parasites, so any such effort would require ongoing monitoring of both the host and parasite population to see if the translocation has been successful, or what effects this might have on the host population.

Aside from conserving parasites simply out of principle, there is also a more host-centric reason for protecting them. Exposure to parasites during early stages of the shearwater's life might be a vital step for them to develop a fully functioning immune system. So those fleas waiting in the nests could be giving the shearwater chicks a needed boost to their immune system early in life that allows them to survive into adulthood.

As mentioned above, there are other parasites that have already been driven to extinction right under our noses. The paper discussed in this post is one of the first to develop a conservation plan for a specific parasite species. Every single species of parasites are unique in their host preferences, life cycles, and distribution, so there won't be a one-size-fits-all plan that can possibly be applicable to all parasitic organisms. Especially when one considers the term "parasite" encompasses countless different phyla of animals, fungi, plants, and single-celled organisms.

Parasites are an integral part of biodiversity, and many of them are facing extinction in the foreseeable future. They deserve to be the target of conservation efforts just as much any other species. If our goal is to protect and conserve "wildlife", we shouldn't forget about the numerous wildlife which are small and hidden from plain sight.

Reference:
Kwak, M. L., Heath, A. C., & Palma, R. L. (2019). Saving the Manx Shearwater Flea Ceratophyllus (Emmareus) fionnus (Insecta: Siphonaptera): The Road to Developing a Recovery Plan for a Threatened Ectoparasite. Acta Parasitologica 64: 903-910.

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