In the Galapagos, a vampire fly threatens the survival of Darwin's finches

Darwin's finches are one of the endemic species of the Galapagos Islands.However, due to a fly, mistakenly introduced by man, they are at risk of extinction.

Two large windows through which the sun enters.Microscopes and slides, notebooks.A round picture in the center of which there is a flea dead, but perfectly preserved. A pungent odor of alcohol used to maintain the sterile environment.On the walls, a series of tall white shelves on which glass cases full of flies and post-its rest.

We are at Charles Darwin Foundation, in the'Santa Cruz Island, one of the mainGalapagos archipelago, where Dr. Paola Lahuatte coordinates the laboratory where the reproductive physiology of the fly which is threatening the survival of many species land birds who reside on the islands.

“In size and color it is completely similar to the common fly – says Dr. Lahuatte – and, instead, it is Philornis Downsi, an invasive alien species which we have dubbed the avian vampire fly.”As she speaks, she observes fascinated the small dipterans crowding the display cases, their new habitat.

“The adult females of this insect lay their eggs in the nests of terrestrial birds, on top of the chicks or on the beak, inside their nostrils.After one or two days, the blood-sucking larvae emerge and slowly begin to apostatize to the base of the nest from where they emerge at night, so as not to be discovered, and continue to feed on the blood and tissues of the newborns.Hence, the nickname vampire.The larvae pupate at the base of the nests after about seven days and emerge as adults over the next two weeks,” explains Dr. Lahuatte.

Although no impacts on seabirds have yet been detected, the presence of the fly has enormous consequences for the biodiversity of the archipelago "because there is no natural enemy of the species that can control its spread". Among the most affected birds are Darwin's finches – emblematic animal of the islands whose observation allowed the namesake scientist to develop the theory of evolution – and, in particular, the mangrove finch.

Barely survived theinvasion of domestic cats and rats, the latter lives in a very narrow range, which makes it even more fragile.

“In this species, of which only around one hundred specimens remain, chick mortality is now one hundred percent, which also reflects on another fundamental aspect for its survival.Dying directly in the nest, no specimen reaches adulthood and, to date, the reproductive outcome is zero.In other words, there are not enough sexually mature individuals that can reproduce which is favoring episodes of hybridization with other species."

Paola Lahuatte

An alien introduced by man

As often happens when we talk about introduction of alien species – that is, they find themselves colonizing a territory different from their historical range – man has played a role in this case too a sadly fundamental role even if not aware.

Analyses entomological studies have in fact made it possible to trace the entrance of the fly to the Galapagos to the sixties when it would have been accidentally introduced by man through some load of fruit – which the specimens feed on in their adult form – or through raw materials such as wood which, inside them, hid the larvae.Once "landed" in the archipelago, she quickly cholonized the environment taking advantage of theabsence of predators and the wealth of prey totally unprepared for the dangerous invasion.

At the moment the presence of the fly was confirmed in all islands – with the exception of the most remote ones such as Wolf, Genovesa, Espanola and Darwin – and concerns 18 species of land birds, of which sixteen are endemic.The result is a increase in direct mortality or, at best, one decrease in life expectancy due to malformations of the beak – where the flies they usually lay eggs and the larvae begin their life cycle – alla reduction in the growth rate, to the point of anemia.

The situation is so serious that a team of scientists works every day in the laboratory coordinated by Dr. Lahuatte relentlessly to steal the secrets of this small but equally powerful insect, in order to learn as much as possible about its reproductive habits so as to be able to control its spread soon.

“If we do not fully understand his behavior, we cannot hope to win this battle.This is why we work with both larvae and adult specimens.Our goal is to domesticate an ever-increasing number of flies, convincing them that this is their natural habitat and therefore forcing them to breed in the cases.To date we are able to obtain a production of around four hundred specimens per week but we want to reach millions of individuals within the next two years".

Among the challenges that the laboratory has had to face in growing healthy flies is the feeding of the larvae which, although they certainly cannot be considered intelligent - at least not in the most common meaning of the term - they certainly are pretentious:in fact, to convince them to eat, every day they are served real pellets composed of blood chicken provided by afarm which researchers periodically visit.

Sterilization:a deception with a good purpose

Although when dealing with alien species, eradication is often one of the preferred strategies, in one context extremely delicate like that of the Galapagos, and being a small and already widespread insect, it was necessary to act on multiple fronts:among the control options adopted are capture through bait and attractive substances for insects, the use of chemical products and the nest treatment of birds with low-risk products.

Furthermore, as soon as the colony of flies bred in the laboratory is large enough, a sterilization campaign supported byInternational Atomic Energy Agency which was available to provide the laboratory with the tools needed to irradiate insects during the development period.

"In this way we will render the spermatozoa harmless of males without either them or the females realizing it.We will literally make fun of them by letting them continue mating but to no avail,” continues Lahuatte, smiling.

The Galapagos:the archipelago where wildlife still has faith in humans

Despite their isolation from the coast of Ecuador, the Galapagos have never managed to escape the influence of man.Since their discovery, which occurred in 1535, when Tomás de Berlanga, bishop of Panama, there landed by mistake, have suffered invasions, land transformations, overexploitation and pollution.Some of the most emblematic of the 1300 species endemics living in the archipelago, have been persecuted for their flesh, for their skins, their fins or even just for the pleasure of seeing them succumb to the power of man.

Yet, every day, huge colonies of sea ​​lions they continue to share their beaches with groups of enthusiastic tourists.Blue-footed boobies and magnificent frigate birds fly over the fishing boats while clumsy pelicans patrol the piers waiting for some scraps from the catch. Sea turtles emerge, from time to time, to take a look at the new arrivals and, without fear, doze in the waves... In what continues to be an exceptional demonstration of trust towards human beings.