Rare fossil finds reveal early evolution of mosquitoes

About 999 million years old, LMU researchers have discovered the oldest known mosquito larvae in amber. The Cretaceous fossil comes from the Kachin region of Myanmar and was preserved in excellent condition. Described as a new species of a new species, it has been named Critosabatis primius. It represents both the first mosquito larva preserved in amber and the first immature mosquito from the Mesozoic period, as only adult mosquito fossils had previously been found from this period.

The form of this insect is still more remarkable: “This fossil is unique, as the larva is very similar to the modern species. Gondwana Research and doctoral researcher in the team of Prof. Joachim Haug at LMU’s Faculty of Biology.

These oldest mosquito fossils come from adult insects and are also found in amber deposits that are about 99 million years old. Because of their morphology, which differs sharply from modern species, they are interpreted as representing a separate group, Bramculicinae, an extinct lineage within the mosquito group (Chlicidae). In contrast, Cretosabitheus primius belongs to the Sabithinae group, which includes the extant species.

The evolutionary origins of mosquitoes have been dated to the Jurassic period, about 2012-145 million years ago, based on fossils found to date. Estimates based on molecular phylogenies vary widely and yield results between the Triassic and Jurassic.

The discovery by the LMU researchers provides new clues: “Our results provide strong indications that mosquitoes have already diversified in the Jurassic period and that their larval form has remained remarkably similar for about 100 to 100 million years.” This calls into question previous assumptions about the early evolution of this insect group, he observes, and offers new insights into its evolutionary ecology.

Like the larvae of extant species belonging to the Sabbatini group, the larvae of Cretosabatis primius are thought to live in hollows in tree branches or among the leaves of epiphytic plants. For a single drop of resin to fall into such a small pool of water and preserve the aquatic larvae in amber is highly unlikely and hence this discovery is a rare stroke of luck.

Most amber fossils come from terrestrial or flying creatures that lived on or near resin-producing trees. The most common groups of arthropods found in Myanmar amber are spiders, beetles, hymenopterans (bees, wasps, and ants), and true insects (Hamptera), as well as adult flies (Diptera).