Triops Longicaudatus
Triops Longicaudatus Red
Triops Longicaudatus
Triops Longicaudatus Red
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Palaeontology: Fossils from the Lower Cretaceous period reveal astonishing facts about male mosquitoes
Seemingly small and inconsequential, except for the agonising nights of hot summers they cause, mosquitoes are considered one of the deadliest species for humans. Their bites transmit numerous infections and are behind most deaths and diseases that affect humans. A revolutionary discovery has thrown up the theory that only female mosquitoes feed on blood. The specimens found in amber could provide the key to unravelling the mysterious behaviour of mosquitoes.
Carrier of infectious diseases
It was previously known that only female mosquitoes need blood as a food source in order to develop their eggs. Proteins and nutrients that are essential for egg development are not obtained from plant food alone. Blood provides these necessary substances. The blood-sucking nature of the female mosquito makes it a major vector of infectious diseases such as dengue, malaria, Zika virus and yellow fever. These diseases cause around 750,000 deaths every year. Malaria alone kills 600,000 people a year, mainly children, and a further 200 million are unable to work for days because they fall ill.
The difference in diet is also reflected in the anatomy of male and female mosquitoes, particularly in the proboscis, which is used for feeding. The proboscis of males is not capable of penetrating the skin, while the proboscis of females is equipped with six powerful needles to suck blood from living creatures. The diet of male mosquitoes is mainly based on sugar sources such as flower nectar, plant sap and other carbohydrate-rich fluids that provide energy for flying, reproduction and metabolism. To facilitate transmission, the mosquito’s hypopharynx, the sixth needle, injects saliva into the victim’s bloodstream. In addition to pathogens, this saliva contains anticoagulant substances that facilitate blood flow and accelerate absorption, which explains the itchy reaction to the mosquito bite.
The previous assumption that, from an evolutionary perspective, only female mosquitoes feed on blood has been called into question by a study recently published in the journal Current Biology. In two male mosquitoes preserved in amber, stinging mouthparts with toothed jaws were discovered, which are considered to be the oldest in arthropods. These specimens originate from the Middle East, more precisely from Lebanon.
The 125-135 million year old amber contains one of the oldest ecosystems in the world and is invaluable to science. The discovery of these two Cretaceous male mosquitoes with piercing mouthparts has revolutionised our understanding of the evolution of blood uptake in insects, as it suggests that male mosquitoes were probably also blood-sucking at this time.
Why this behaviour has changed over time remains unclear. The authors of the study speculate that blood proteins may have increased the male mosquitoes’ ability to fly and mate in the Cretaceous period. In 2015, the DNA material of Anopheles mosquitoes was analysed in a genome study. Researchers discovered genetic sequences that have no clear origin in the evolution of mosquitoes. These genetic segments do not appear to belong to any known lineage of mosquito evolution and were labelled “ghost lineages” as they could not be clearly assigned to any existing mosquito species.
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