Pathogenic Fungus on the Cicada
The Pathogenic Fungus on the Cicada infects and kills the insect. Milind Vachhani recounts his experience of research from their recently travelled photography tour at Agumbe Rainforest Research Station with Vipul Ramanuj (Wildark) in July 2018.
Many cicada species suffer from fungal pathogens belonging to the genus Massospora. These fungi destroy the reproductive organs of males and cause them to behave like female cicadas — in the case of Magicicada cicadas, they flick their wings instead of singing — and they attempt to mate with other males, thus spreading the fungus.
Scientists now know in gruesome detail exactly how the fungus Massospora cicadina infects so many cicadas, before going on to hijack their behaviour and explode out of their abdomens, leaving the cicadas compelled to mate despite no longer have sexual organs. The fungus is already infamous because it takes over the cicada’s abdomen, as you can see in the picture, bursting out from it to scatter its spores, and leaving the cicada with little below the waist, so to speak.
As cicada nymphs prepare to emerge after spending up to 17 years maturing underground, resting spores stuck to its exoskeleton are alerted by compounds on the cicada that it’s time to infect and sprout. The fungus also settles in the cicadas’ abdomens, affecting both males and females. But early on, the males start acting a bit weird. In addition to normal mating behaviours, they start flicking their wings in a manner seen only in females. It turns out, this is so they can transmit the fungus sexually.
This normally female behaviour lures in other males who will try to mate with them – but instead, they pick up the fungus themselves. And the affected males will also try and mate with females, transmitting the fungus to them, too. And, of course, infected females will transmit the fungus to unaffected males who try to mate with them.
The spores gradually fill the abdomens of all the affected cicadas, to the point of bursting them open, or in some cases even falling off entirely, scattering spores of the white fungus out of the cavity where their butts used to be. This final act causes the cicada’s sexual organs to fall off, too, but they still feel compelled to mate.
Cicadas infected by other cicadas have what the researchers call a Stage II infection, and they follow the same infection cycle. They continue to behave normally, infecting other cicadas, and dropping spores wheresoe’er they roam.
Behavioural changes caused by parasites have been observed in many other species, including ants, snails, crabs, beetles, and even rodents, and the field is one that is proving of increasing interest to science, the researchers noted.
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