Scientists have uncovered why some amphibian populations are making a comeback after being devastated by a deadly fungal disease that wiped out frogs and toads around the world.
The study, led by University College London (UCL), ZSL and Imperial College London, found that the timing of immune development in amphibians plays a key role in whether they survive infection. The research results were published in a magazine natural chemical biology.
A deadly fungus that targets adult amphibians
chytrid mold, Batrachochytrium dendrobatidis (Bd) has caused catastrophic declines in amphibian populations around the world. This fungus causes chytridiomycosis, a disease that damages the skin of frogs and toads and destroys their ability to regulate water, salt, and minerals.
Tadpoles and larvae lack keratin-rich skin, so young amphibians are primarily protected. Bd Eat. As they transform into adults and their skin becomes keratinized, they become vulnerable to infection, often causing mass mortality.
To better understand why some populations recover while others continue to collapse, researchers studied common midwife toads that live around four lakes in the French and Spanish Pyrenees, all of which had severe experiences. Bd occurrence.
In some lakes, toad populations were still declining and almost extinct. However, in the other three lakes, populations recovered even though the fungus remained present in the environment.
Early immune protection makes the difference
The research team focused on antimicrobial peptides, natural chemicals that are released by amphibian skin and function as an important part of the immune system.
They found that toads in the recovering population developed these protective peptides much earlier, when they were still tadpoles. By the time we reach adulthood and become more susceptible to infection, Bdtheir immune defenses were already well established.
In contrast, toads from distressed populations produced much less of these protective peptides during the tadpole stage and were not ready for them once they reached adulthood.
Lead author Dr Philip Jarvis, from UCL Chemistry, ZSL Animal Research Institute and Imperial College London, said: “Our study shows that species that have been severely reduced by this disease can still recover, although they have the tools to fight the infection. , it’s all about timing. The disease kills toads and frogs as they grow from tadpoles to adults. Gaining mature immunity during the tadpole stage helps these toads survive and the population persists.”
Dr Jarvis added: “The next step is to look at the factors that prevent these immune systems from maturing early. This could be genetic or due to environmental factors such as temperature or the presence of trout. This could be a big risk to the tadpoles, allowing them to grow into adults and get out of the water sooner, giving them less time to develop their immune systems.”
Over 1,100 hidden immune peptides discovered
To investigate the toads’ chemical defenses, the researchers used mass spectrometry to examine a mixture of peptides (short chains of amino acids) released from the toads’ skin.
This analysis revealed a much larger collection of immune peptides than scientists expected. Of the 1,152 peptides identified, only seven had been previously documented.
The study also found that tadpoles that produce a greater variety of peptides (i.e., have matured defenses before becoming toads) are much more likely to survive despite the continued presence of peptides. Bd occurrence. Populations with low peptides at the tadpole stage continued to suffer from high mortality rates.
Research results could provide inspiration for future medicines
Senior author Professor Alethea Tabor (UCL Chemistry) said: “We have discovered a much greater diversity of peptides than expected. We now need to understand how they work to control pathogens and which peptides have antibacterial properties.”
“Many human medicines were first discovered in nature; penicillin, for example, comes from fungi. Therefore, these peptides are new leads that can be used to help human health. Especially since we have our own problems as a species with increasing antimicrobial resistance and need to find new ways to treat infectious diseases.”
Mass spectrometry allows scientists to measure the mass of molecules with great precision. In this study, the researchers used tandem mass spectrometry at UCL Chemistry to split peptides into smaller fragments, measure those fragments, and reconstruct the structure of each peptide. This process enabled the team to identify and sequence hundreds of previously unknown molecules.
Co-author Dr Kersti Cull (UCL Chemistry) said: “The ability to analyze hundreds to thousands of molecules in parallel has only emerged in the last decade. This approach has been more commonly applied in human health research, for example to differentiate cancer cells from normal tissue, but is increasingly being extended to other areas of biological research.”
The research was funded by the UK’s Natural Environment Research Council (NERC) and the Leverhulme Trust.
