March 17 () –
The largest known genome of any insect, seven times the size of the human genome, has been discovered in a rare grasshopper from Central Europe.
In a study published in PLOS ONE, researchers from the German Leibniz Institute for the Analysis of Change in Biodiversity (LIB) and the Czech Academy of Sciences show that the idea that insect genomes are comparatively small and less complex is wrong.
The Spotted Humming Grasshopper (Bryodemella tuberculata) it is nearly extinct except for a small number of populations on the riverbanks of the Alps. These threatened habitats have been shaped by thousands of years of constant change through the natural dynamics of rivers.
“Possibly, this adaptation to variable environmental conditions has fostered genetic diversity and has led to exceptional genome sizes,” he says. it’s a statement the hypothesis of Oliver Hawlitschek, head of the LIB genetics laboratory in Hamburg. “At the same time, compared to humans, we see that the size of the genome is not necessarily related to the level of complexity of an organism.”
This study is the most recent in a series of publications on the evolution of genome size in insects in the context of their evolutionary and biogeographical history. None of these papers have answered the question why, among all insects, the genomes of some grasshopper species are exceptionally large. Most insect genomes are much smaller, like that of the fruit fly, whose size does not exceed one sixth of the human genome.
The size of genomes varies considerably between different groups of animals, sometimes even within groups. Since the entire genome must duplicate itself during each cell division, scientists are looking for the reasons behind this variability. They are trying to understand the architecture and content of the genomes, but there is still a long way to go. Data on genome size is available for only 1,345 of the more than one million known insect species. All of the largest genomes have been found in grasshoppers and crickets.
To better understand genome size variation in grasshoppers and their evolutionary history, the researchers measured the genomes of 50 species using flow cytometry, investigating variability in related species. They found the largest genome in the spotted humming grasshopper (Bryodemella tuberculata), replacing the previous record holder, the Asian desert cricket (Deracantha onos).
Oliver Hawlitschek sees more detailed sequence-based genomic analyzes as a way to learn more about the evolutionary mechanisms that determine the size of genomes. “I am sure that studying these extremes will also provide us with many insights into the function of our human genomes.”
