With the discovery that the medium ground finches produce antibodies aimed specifically at the parasites – a pox virus and a nest fly – “the next step is to determine if this immune response is helping the birds or hurting the birds,” says University of Utah biology Professor Dale Clayton, who led the new study.
One cannot assume the immune response will help because antibodies also can be involved in autoimmune diseases and allergy symptoms.
Nevertheless the new study is significant because “these finches are icons of evolution, and the icons are in danger of extinction,” Clayton says. “Are they sitting ducks? Are they sitting finches? To answer that, the first question is, does the immune system recognize the parasites? And this study shows, yes it does.”
The study will be published online Wednesday, Jan 6. in PLoS ONE, a journal of the Public Library of Science.
Clayton says a key finding is that “wild species can respond to invasive parasites with which they have no history of association. The immune system has been activated.”
Development of antibodies “shows the birds may have the ability to fight back,” says Jen Koop, a University of Utah doctoral candidate and study coauthor.
Koop and Clayton say that, to their knowledge, the study is the first to show a wild bird species produces antibodies aimed specifically at different classes of parasites.
Earlier studies found immune responses by birds injected with a foreign substance, but those responses are general, not specific to a real parasite, Clayton adds.
Clayton and Koop conducted the study with first author Sarah Huber, a former University of Utah postdoctoral researcher and now an assistant professor at Randolph-Macon College in Virginia. Other coauthors were entomologist Jeb Owen and zoologist Marisa King of Washington State University; and Princeton University evolutionary biologists and 2009 Kyoto Prize winners Peter and Rosemary Grant, who have studied Galapagos finches for decades.
The new study was funded primarily by the National Science Foundation.
A Tale of Two Parasites
The study involved two parasites that invaded the Galapagos Islands, off the coast of Ecuador. One is the pox virus, Poxvirus avium. Koop says it “creates lesions on non-feathered parts of a bird – around the bill, eyes, legs and feet. Toes and feet can fall off.”
The study’s main focus was the other parasite, the nest fly, Philornis downsi, which was introduced to the Galapagos as early as 1964. The fly larvae infest finch nests and attack featherless skin, impairing the growth of nestling birds and even killing them.
“The flies can create open sores on nestlings, and decrease survival,” Koop says.
There are 15 species of finches in the Galapagos. All evolved from a common ancestor. Darwin observed changes in their beaks and other features over time, so “they figured prominently in his thinking about how new species evolve,” Clayton says.
The Galapagos is “the most famous group of islands that hasn’t had any native birds go extinct yet,” Clayton says. “Many of the native species in Hawaii, for example, have gone extinct because of humans,” who introduced mosquitoes with malaria as well as predators such as cats and rats, destroyed habitat and hunted birds for feathers.
No native birds have yet gone extinct in the Galapagos because “there were few people living there until the mid-1800s,” he adds. That may change with the introduction of nest flies from elsewhere in South America and of mosquitoes that carry the pox virus.
The new study and ongoing work aim to determine whether “the birds are able to fight back, do they have defenses, or have they just been blindsided because they have no evolutionary history with these parasites,” Clayton says.
The Study and Its Findings
The researchers collected ground finches in 2008 at two Galapagos islands about 5 miles apart: Isla Daphne Major and at El Garrapatero on Isla Santa Cruz. Nest flies were found on both islands, but pox virus was found only on Daphne Major.
The birds were captured using nets and baited live-animal traps. Before release, each bird was fitted with leg bands for future identification.
On Daphne Major, the Grants, Huber and Koop captured 30 finches and noted whether the birds had pox sores or signs of prior pox infection, like scarring or lost toes.
On Santa Cruz, they examined finches before and during nesting, which is when the birds are exposed to fly larvae that infest their nests. They captured 37 birds exposed to nest fly larvae, and 76 that were not. They found 96 percent of nests were infested.
On both islands, the researchers collected a small blood sample from a wing vein in each bird. They used what are known as ELISA tests to check the finches’ blood for antibodies to both the pox virus and nest flies. Study coauthors King and Owen developed a way to use the method to test for finch antibodies to both parasites.
"This study develops a tool that can be used to survey the rest of the Galapagos to determine which populations of birds have been exposed to the parasites and which have not been exposed,” says Clayton. “The tool could be used to see if birds on some islands are better than birds on others at fending off the parasites.”
The new study found:
-- Finches on Daphne Major had an antibody response to pox virus three times stronger than the response by Santa Cruz finches, which showed no signs of the virus.
-- Finches on Santa Cruz that were tested during nesting had an antibody response to nest flies 1.7 times stronger than the response by birds tested before nesting.
Host vs. Parasite: An Evolutionary Arms Race
When parasites invade a “naïve” population, “the question is can the host evolve defenses fast enough,” Clayton says. “It’s what we call in evolutionary biology an arms race between the host and the parasite.”
It is unlikely the finches already evolved defenses to the pox virus and nest fly, but for yet-unknown reasons, they “have genetic diversity that lets them mount immune responses to parasites, including ones they haven’t seen before,” he adds.
Koop now is studying whether the finches’ immune response helps them or makes them feel ill and less likely to mate, feed chicks, watch for predators and defend territory.
Clayton says such research is urgently needed “because in theory these flies could lead to rapid extinction of bird species” – and not just finches – in the Galapagos.
“Species have long histories of evolving together,” says Clayton. “This can lead to a balance. The parasites use hosts but don’t drive them extinct because the hosts fight back. But if you pick up a parasite from one spot on Earth and drop it on another spot – something people are doing frequently – then the host animal may not have a chance. There are lots of invasive parasites. This is a big problem worldwide.”University of Utah Public Relations
| Newswise Science News
The balancing act: An enzyme that links endocytosis to membrane recycling
07.12.2016 | National Centre for Biological Sciences
Transforming plant cells from generalists to specialists
07.12.2016 | Duke University
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
07.12.2016 | Health and Medicine
07.12.2016 | Life Sciences
07.12.2016 | Health and Medicine