Guwahati: Scientists have discovered a new mosquito species in the forested villages of Tripura that looks almost identical to the known dengue and chikungunya vector Aedes albopictus, but is genetically distinct.
The finding, published in Scientific Reports, reveals the existence of a cryptic species, provisionally named Aedes nr. albopictus — marking the first such discovery in India and only the third reported worldwide.
Researchers from the ICMR-Regional Medical Research Centre, Northeast Region, and collaborators uncovered this hidden twin while studying mosquito populations across five districts in Tripura. At first glance, the mosquitoes appeared to be ordinary Ae. albopictus, easily recognized by the white stripe running down their back.
However, molecular studies told a different story — beneath the familiar exterior was a genetically distinct species that diverged from Ae. albopictus around 36 million years ago.
The “nr.” stands for “near,” indicating its close genetic relationship to Aedes albopictus. Out of 139 specimens that morphologically resembled Ae. albopictus, 14 were found to be other species when subjected to molecular methods. The study was conducted using archived Aedes samples collected from five districts of Tripura — Dhalai, Gomati, Sepahijala, Unokoti, and West District — from 2019 to 2022.
“Our study uncovered another mosquito species that is morphologically similar to Ae. albopictus but genetically different,” the researchers said.
Importantly, the study also describes a distinct feature in the male genitalia, reported for the first time, further confirming the new species.
“This discovery highlights the possibility of sympatric speciation of Ae. nr. albopictus,” the researchers added. “It is a significant step toward better understanding the evolution of Aedes species, their breeding sites, and the transmission dynamics of dengue and chikungunya in rural, forested areas of Tripura.”
Sympatric speciation occurs when a new species evolves from an existing one without being separated by a physical barrier like a river, mountain, or distance.
Phylogenetic analysis, nucleotide diversity, and genetic distance showed that these mosquitoes are genetically distinct from Ae. albopictus and other Aedes species. Though related to cryptic Ae. albopictus species from Vietnam and China, the researchers found three new haplotypes (Hap_1, Hap_2, and Hap_4). “This is the first report of Ae. nr. albopictus and its co-breeding with Ae. albopictus in rubber collection bowls,” they said.
A time tree estimated that Ae. nr. albopictus and Ae. albopictus diverged about 36.13 million years ago, with Ae. aegypti as the older ancestor (~46 million years ago). “These results match previous studies and support that Ae. nr. albopictus is a separate species,” the researchers said.
One of the key findings is that Ae. nr. albopictus does not carry Wolbachia. In Ae. albopictus, Wolbachia infections help mosquitoes resist viruses like dengue and chikungunya. Without this natural shield, Ae. nr. albopictus could potentially be a more efficient virus transmitter.
“Many questions remain unanswered because Ae. nr. albopictus has only just been discovered,” the researchers said. They still don’t know if this mosquito has special preferences for breeding sites or whether certain mating barriers led to its evolution before or after mating. Other unknowns include how it behaves differently from Ae. albopictus in terms of resting, feeding, and response to existing mosquito control methods. Its ability to spread diseases also remains uncertain, especially since it doesn’t carry Wolbachia, a helpful bacterium found in Ae. albopictus.
Another major mystery is how new mosquito species like this one become reproductively isolated — meaning they can no longer breed with closely related species — even when they still look almost identical.
While studies on other mosquitoes, such as malaria-carrying Anopheles species and the Mariae complex, have shown different ecological habits and clear reproductive barriers, very little is known about how reproductive isolation happens in species like Culex and Aedes albopictus.
The discovery raises important public health concerns, especially for regions already battling mosquito-borne diseases. Adding to the challenge, Ae. nr. albopictus and Ae. albopictus share the same breeding sites, including rubber collection bowls and household containers. With no obvious physical differences, standard mosquito surveillance based only on appearance could easily miss the cryptic species.
The findings also hint at a broader issue: the likelihood that other cryptic mosquito species remain undiscovered in India and elsewhere. Morphological similarity can mask important genetic differences, potentially affecting outbreak management and mosquito control strategies.
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