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Popular Science: Who lives in birds’ feathers?

An international scientific team including a member of our faculty described new host relationships between Mallophaga (taxon Ischnocera: Philopteridae) and birds. New observations show that life and evolutionary relationships of Mallophaga are much more complicated than we could conceive before.

Birds are not what they seem to be. From a biologist’s point of view, they are not isolated individuals but literally flying ZOOs. Only in their plumage and on their skin dwell a great amount of Acarina, feasting on keratin, flies (Ornithomya avicularia) sucking blood and a great variety of Mallophaga, living from skin, feather and drops of blood.

Middendorff's grasshopper warbler (Locustella ochotensis), host of Mallophaga Philopterus acrocephalus. Photo: commons.wikimedia.com.

Mallophaga are small and unobtrusive, hardly discernible, occurring in ample amounts and in assorted forms. Several generations of specialists have already studied these tiny creatures – and still, a mountainous amount of work is waiting for scientists of today... and of tomorrow. In the past, the prevalent idea was that for every bird species there is one specific species of Mallophaga. It was not discovered until later that Mallophaga are capable of changing their hosts. Today, there is evidence that Mallophaga “travel” from one host to another, for example on the back of Ornithomya flies! Even now, there are many unanswered questions regarding the lifecycle of various Mallophaga species, about their role in the hosts’ lives and their relationships with other parasites. Do Mallophaga transmit any diseases? Are they considerably harmful for their hosts? Are they able to protect their hosts from other parasites? – So many questions for future researchers!

Moustached warbler (Acrocephalus melanopogon), another host of Mallophaga Philopterus acrocephalus. Photo: commons.wikimedia.com.

The authors of the paper were the first to publish any evidence of occurrence of Mallophaga Philopterus acrocephalus in Middendorff's grasshopper warblers (Locustella ochotensis). Hitherto, the occurrence of this species has been known only in warblers (f. Acrocephalidae). Authors have also described a new species – Philopterus gustafssoni – parasitizing kinglets (gen. Regulus).

Goldcrest (Regulus regulus), host of newly described Mallophaga. Photo: commons.wikimedia.com.

For more information we interviewed first author of the paper MVDr. Tomáš Najer Ph.D., Czech University of Life Sciences, Prague):

Q: “Are Mallophaga Philopterus acrocephalus able to ‘travel’ between Moustached warblers and Middendorff's grasshopper warblers? And if so, how do they achieve it?”

A: “Some kind of travelling between these two groups is highly probable. What we still do not know is, which of these is the original host of this Mallophaga. Members of the genus Philopterus are not highly mobile, so it seems most likely to us that they use bloodsucking flies (Ornithomya avicularia). This manner of host changing has been already proved in closely relative groups. These flies have their abdomen covered with robust hairs and Mallophaga can hold on to them fast, like they hold feathers of the birds they invade. When the fly walks in the feathers of a bird invaded by Mallophaga, the latter parasite catches the abdominal hairs, holding them until the fly touches down on another bird – and there it releases its grip.” 

Q: “How many species of Mallophaga do we recognize in kinglets so far? Is this species exceptional in any way?”

A: “Recently, there are two Mallophaga species known as parasites in kinglets. The most remarkable thing about the species described in our study is probably that it may not be completely ‘newly discovered’ as it may seem. The oldest records about Mallophaga in kinglets date to 1842. Mallophaga were then considered to be host-specific. In other words: one bird species – one Mallophaga species. But, surprisingly, the situation was different specifically in the case of that bird individual in which any Mallophaga species parasitising in kinglets was described for the very first time. The parasite was a renegade who evidently had left its original host for the kinglet it was observed on. Actually, it was a member of a totally different species, usually not occurring in kinglets’ feathers at all. Findings of Mallophaga in kinglets became more copious with the time, but no-one checked whether the newly found Mallophaga were actually of the same species as that found in 1842. Determination of the species was always unquestioningly copied again and again... for the last time in 2017. When our team was going to determinate collected exemplars of Mallophaga, we suddenly realised that our material differs widely from that first described individual. This is how we discovered and described a new species.

Q: “Who is the new species named after?”

A: It is named after my friend and colleague Daniel Gustafsson. He recently challenged research on Mallophaga in China. Curiously, Chinese scientific literature never included any written work focused on this topic. His findings are highly interesting –he was the first to describe a new Mallophaga species parasitising in trogons. This Mallophaga is completely different from all that we knew in trogons before. It is closely related to the mentioned species parasitising in kinglets and warblers. But this group is not present in other small songbirds in China at all – it is unclear how it came to occur in trogons. And it is well known that trogons do not make long-distance travels.”

Newly described Mallophaga Philopterus gustafssoni, parasitising in kinglets. Source: authors of the article.

Q: “Which role do Mallophaga play in the lives of their hosts?”

A: “For most healthy birds in good shape, Mallophaga are not any serious problem. Hitherto, no transfer of dangerous illnesses has been demonstrated. In addition, birds have many possibilities to get rid of them continuously. Problems can occur if the bird is weakened, e.g. due to an infection or poor nutrition. If the usual defence mechanisms are less effective than in normal conditions, Mallophaga take advantage of the situation and increase their number. Each group of Mallophaga causes specific difficulties: the species living on feathers cause the invaded bird heat losses, and the species feeding on blood and pieces of skin may open the entrance for infectious diseases. Excessive population of Mallophaga may weaken the bird up to its death.”

Q: “What kind of impulse brought you to the research of bird parasites?’

A: “I was lucky enough to meet great people at the right time. Mallophaga is an uncommon field of research – globally there are about 40 people specializing in it. This has an unavoidable consequence – all these people know each other personally, meet regularly and work as a kind of big family. It was by mere chance that I attended one of these meetings as a student, looking for a field to focus on... I was enthralled by the friendly, homely and inspiring atmosphere. It was so strong that I never thought seriously about any other field of research. It must be said, anyhow, that my then supervisor Assoc. Prof. Oldřich Sychra played an instrumental role in this. His support and patience were crucial for me during the difficult moments”.

Q: “How should an ideal researcher of Mallophaga and their lives look like?”

A: “Should be a polymath, ideally... Due to high specialisation of this topic, it is quite possible that starting with some searching, one may be the only person in the world working on it. This requires a good deal of independence and self-control. Usually, you are never part of a big team. This means that what you do not achieve by yourself may never be realised. As for fields of study that may be very helpful for anyone dealing with Mallophaga, first and foremost I should mention ornithology.”

Najer, T., Papousek, I., Adam, C., Trnka, A., Quach, V. T., Nguyen, C. N., ... & Sychra, O. (2020). New records of Philopterus (Ischnocera: Philopteridae) from Acrocephalidae and Locustellidae, with description of one new species from Regulidae. European Journal of Taxonomy, (632).

Roman Figura

Published: Dec 14, 2020 08:55 AM

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