by Piter Kehoma Boll
Two mosquitoes of the genus Aedes, Aedes aegypti and Aedes albopictus, are invasive species in tropical and subtropical regions worldwide. While A. aegypti is native from Africa, A. albopictus is originally from southeast Asia, but both species have been spread by humans and continue to increase their range.
Both species are known as vectors of several diseases that affect humans, especially those caused by Flavoviruses, which include the Yellow fever, Dengue fever and Zika fever. Chikungunya, caused by a species of Alphavirus is also transmitted to humans by them. Moreover, they can also transmit some nematodes, such as the heartworm that infects the heart of dogs and other carnivores.
Because A. aegypti and A. albopictus pose such a huge threat to public health, getting rid of them is top priority. Here in Brazil, there is a massive national campaign to reduce the ability of Aedes to reproduce by avoiding containers with still water in the open, such as flower vases, buckets, uncovered barrels, discarded tires and virtually everything that can retain water long enough for the larvae to develop. I have to say, though, that this all seems to be useless. The mosquitoes continue to spread and the cases of dengue fever continue to grow. The fact is that the mosquitoes will find a place to lay their eggs. If they don’t find it in your backyard, they will find it in the forest or any vacant lot.
Instead of forcing them to lay their eggs where we cannot see, we should stimulate them to lay their eggs around us and then kill the larvae. Several aquatic predators have been tested as potential allies, including larvivorous fish, dragonfly nymphs, copepods, planarians and even other mosquitoes whoses larvae eat the larvae of Aedes! The use of these predators showed mixed results. Larvivorous fish are difficult to maintain in water tanks at home and dragonfly nymphs are too generalist as predators.
Now a new predator has been suggested: a plant! Yes, a carnivorous plant of the genus Utricularia, which includes species known as bladderworts. These aquatic plants have little bladder-like structures that function as traps to capture small animals. The bladder is hollow and has an internal negative pressure in relation to the environment surrounding it. This negative pressure is created by water being constanly pumped out of the bladder through its walls via active transport. The bladder’s opening is covered by a small lid that avoids water to fill it again when the trap is set. Surrounding the lid, there is a group of bristle-like protuberances. When an animal is moving through the water and moves one of those bristles, they slightly deform the lid, breaking the seal and allowing water to enter the bladder. The negative pressure then sucks water quickly into the bladder, dragging the small animal with it. Then it is only a matter of time for the poor animal to be digested.
A group of researchers at the University of Rhode Island, USA, tested whether Utricularia macrorhiza, the common North American bladderworth, could be an effective predator of mosquito larvae. By adding U. macrorhiza to containers with larvae of A. aegypti and A. albopictus, they were able to kill 95 to 100% of the larvae in only five days. That’s an amazing result, don’t you think?
Since bladderworts are much easier to raise in tanks and other containers in your backyard than animal predators such as fish and dragonflies, they are a promising new alternative to control the populations of this disease-carrying insects.
So, are you eager to raise some aquatic carnivorous plants to help fight these heinous mosquitoes?
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Couret J, Notarangelo M, Veera S, LeClaire-Conway N, Ginsberg HS, LeBrun RL (2020) Biological control of Aedes mosquito larvae with carnivorous aquatic plant, Utricularia macrorhiza. Parasites Vectors 13, 208. https://doi.org/10.1186/s13071-020-04084-4
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* This work is licensed under a Creative Commons Attribution 4.0 International License.