Chromosomal mutations enabled mosquitoes to survive the era of dinosaurs.

In a review article published in the journal Current Opinion in Insect Science (Q1), scientists discuss how chromosomal inversions influence the evolution of one of the most dangerous insects on Earth.

“The subject of our research is chromosomal inversions. This is a type of rearrangement where a segment of a chromosome is rotated 180 degrees,” explains one of the authors of the article, Igor Sharakhov, a scientist at the Biological Institute of Tomsk State University and Virginia Polytechnic Institute. “Chromosomal inversions can provide malaria mosquitoes with traits they previously lacked, such as drought or excessive moisture resistance, tolerance to cold or heat, adaptation to feeding on blood from new hosts, and the ability to cope with new pathogens. Due to the high rate of chromosomal changes, malaria mosquitoes have successfully survived even during mass extinctions of flora and fauna on the planet.”

Compared to large animals like dinosaurs or mammoths, malaria mosquitoes can evolve significantly faster, making them more adaptable to changing environmental conditions over millions of years.

Dinosaurs and mammoths lived for about 70–80 years and reached maturity only at 14–15 years. In contrast, mosquitoes become sexually mature just 7–10 days after developing from eggs. Consequently, mosquitoes can go through several generations in a year, unlike larger animals. Gene and chromosomal mutations occur spontaneously in germ cells, so each new generation presents an opportunity for new mutations that may prove beneficial in such conditions and be passed on to the next generation.

“In previously published studies that I participated in, it was shown that every second letter of DNA (nucleotide base) in the genomes of African malaria mosquito populations is polymorphic, meaning it has a mutant variant,” says Igor Sharakhov. “In comparison, such gene mutations occur 100 times less frequently in the human genome. The gene mutations accumulated through evolution allow mosquitoes to rapidly adapt to environmental changes and develop resistance to various insecticides used for population control.”

Interestingly, the first dinosaurs and mosquitoes appeared on Earth around the same time—during the Triassic period, approximately 240 to 220 million years ago. After the mass Triassic-Jurassic extinction event 201 million years ago, dinosaurs became significantly more diverse and continued to dominate terrestrial vertebrates until their extinction 66 million years ago.

Malaria mosquitoes (genus Anopheles) emerged 179 million years ago. Around the same time, the species diversity of flowering plants began to increase, which provided nectar for both male and female mosquitoes before they engaged in blood-feeding. Some scientists believe that malaria mosquitoes contributed to the extinction of the dinosaurs.

“The fact is that malaria was relatively new at that time, and the immune system of dinosaurs struggled with the Plasmodium parasites transmitted by mosquitoes during blood-feeding,” explains Igor Sharakhov. “Therefore, when the mosquito population increased significantly in the tropical and subtropical conditions of the Cretaceous period from 145 to 66 million years ago, dinosaurs suffered from severe illnesses, unlike modern reptiles and mammals, whose immune systems have developed the ability to fight the disease.”

Thus, dinosaurs were already in a state of decline before their extinction, which was directly triggered by the impact of a meteorite on Earth 66 million years ago. Following the last mass extinction, malaria mosquitoes increased their species diversity and expanded their range of blood hosts, adding mammals and birds to the surviving amphibians and reptiles. Today, there are nearly 500 species of malaria mosquitoes in the genus Anopheles, of which about 40 can transmit human malaria pathogens.

Research has shown how different mosquito species genetically adapt to various conditions. For instance, researcher Vladimir Stegniy from Tomsk State University, along with co-authors, studied the shift in the frequency of temperature-dependent inversions in malaria mosquitoes in response to climate change. They found a tenfold decrease in the frequency of the “cold resistance” inversion 2R1 in two Siberian populations of the Eurasian species An. messeae from 1975 to 2013.

Another interesting pattern is that even among distantly related species that diverged long ago in evolution, similar evolutionary processes occur under comparable conditions.

One of the key conclusions from the studies presented in the review article is that inversion polymorphisms in insects exist and function across different spatial and temporal scales: they can be evolutionarily stable if external conditions change little, or they can arise rapidly in response to drastic changes in the environment. Furthermore, chromosomal inversions influence the evolution of insect genomes, leading to differences between gene variants, which ultimately contributes to the adaptation of species to diverse conditions.