Galapagos Mosquitoes’ New Diet Threatens Giant Tortoise

The Galapagos form of the black salt marsh mosquito has changed its diet to prefer reptile blood instead of feeding on mammals and birds. This discovery has some scientists fearing the introduction of a new mosquito-borne disease which could devastate the Galapagos native wildlife.

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A group of scientists from the Galapagos National Park, the Zoological Society of London, and the University of Leeds found that the mosquito (Aedes taeniorhynchus) is feeding primarily on marine iguanas and the Galapagos giant tortoises, a change from the usual diet of the insect. The mainland version feeds mostly on mammals and birds.

The group’s genetic research found that the mosquito was not introduced by man, as originally thought, but colonized the islands 200,000 years ago. Because few mammal species inhabited the islands prior to the arrival of man about 500 years ago, the scientists believe that the change in the mosquito’s feeding behavior is an adaptation due to its environment.

“When we started the work we thought that this species was also introduced by humans, so it was a surprise that it turned out to be so ancient. The genetic differences of the Galapagos mosquitoes from their mainland relatives are as large as those between different species, suggesting that the mosquito in Galapagos may be in the process of evolving into a new species.” - Arnaud Bataille, University of Leeds and ZSL PhD student

With the increase in tourism, the threat of the introduction of a new disease borne by mosquitoes is increasingly likely, say the researchers. Due to the long isolation from other wildlife, native Galapagos wildlife is not likely to have much immunity to new diseases, and the effects could be devastating.

“With tourism growing so rapidly the chance of a disease-carrying mosquito hitching a ride from the mainland on a plane is also increasing, since the number of flights grows in line with visitor numbers. If a new disease arrives via this route, the fear is that Galapagos’ own mosquitoes would pick it up and spread it throughout the archipelago.” - Dr Andrew Cunningham, Zoological Society of London

The research team believes that instead of attempting to control the Galapagos black salt marsh mosquito, measures should be taken to avoid the introduction of new diseases to the islands. The government of Ecuador currently requires that the interior of planes flying to the Galapagos to be treated with an insecticide, and both the hold and cabins must be sprayed on each flight.

“It is absolutely vital that these control measures are maintained and carried out rigorously, otherwise the consequences could be very serious indeed.” - Dr Simon Goodman, Leeds’ Faculty of Biological Sciences

The research, Natural colonization and adaptation of a mosquito species in Galapagos and its implications for disease threats to endemic wildlife, was published in the Proceedings of the National Academy of Sciences (PNAS).

Images: ©Penelope Curtis, ©Marilyn Cruz

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