JNTBGRI researchers unravel the mystery behind the ‘shooting’ droplets from Theepacha

A recent study suggests the source of the droplets is not the liana as is commonly believed, but the Aloka depressa, a leafhopper that feeds on sap from the kidney-shaped leaves of its host.

Updated - March 12, 2023 07:26 pm IST

Published - March 12, 2023 07:24 pm IST - THIRUVANANTHAPURAM

The leafhopper Aloka depressa perched on a leaf.

The leafhopper Aloka depressa perched on a leaf. | Photo Credit: Special arrangement

Researchers at the Jawaharlal Nehru Tropical Botanic Garden and Research Institute (JNTBGRI) may have figured out the secret behind the water droplets that keep drizzling from the Diploclisia glaucescens, a liana or woody vine known locally as the ‘Theepacha.’

Call it the curious case of the leafhopper, the liana, and, well, insect ‘pee.’

The source of the droplets, it appears, is not the liana as is commonly believed, but the Aloka depressa (tribe Phlogisini), a leafhopper that feeds on sap from the kidney-shaped leaves of its host. The tiny insect sucks nutrients from the sap, and, using a springy stylus on its tail-end, flicks away the waste fluid in the form of teeny-weeny droplets.

First reported phenomenon

The fascinating relationship between the Diploclisia glaucescens and the Aloka depressa and the mystery of the ‘shooting’ droplets are the subject of an upcoming research paper in the journal Plant Biology (the paper has been published online). This is the first time that the phenomenon, dubbed ‘sharpshooting’ by researchers, is being reported from India, JNTBGRI said.

Leafhoppers of the species Aloka depressa.

Leafhoppers of the species Aloka depressa. | Photo Credit: Special arrangement

Field observations and related studies were led by B. Sabulal of JNTBGRI. Team members included S. Ajikumaran Nair, Anil John J., T. Sabu and Gokul B. S. of JNTBGRI, and H. M. Yeshwanth of the National Centre for Biological Sciences, Bengaluru.

As the droplets appear to drizzle down from the liana, the latter gained the moniker ‘rain showering plant.’ But in reality, it is the insect that causes the droplets to fall. The phenomenon has not been reported elsewhere in India. Only a single type specimen of the leafhopper, Aloka depressa, was previously reported from Karnataka, according to the researchers.

‘Super propulsion’ tech

In size, these leafhoppers are tiny. The males are about 6.25 mm in length. A recent study found that the stylus on its rear end serves as a catapult, a sort of insect-realm ‘super propulsion’ tech which helps it fling away the droplet excreta.

Droplet-shooting insects are not unique to India. In the Americas, insects of the ‘sharpshooter’ group infest crops like citrus and grape, feeding on their sap and causing diseases to the host plants. In the case of the ‘Theepacha’ and the Aloka depressa, however, the JNTBGRI study did not notice any ‘health problems’ in the host.

Diploclisia glaucescens lianas growing in the JNTBGRI botanic garden were the subject of the study conducted over a four-year period. The study also revealed the presence of 20-Hydroxyecdysone (20E), an insect molting hormone, in the host plant. 20E was also detected in the droplet excreta of the leafhopper.

Further studies on this ‘sharpshooter’ insect and its intriguing association with the host plant are being carried out at the Phytochemistry and Phytopharmacology Division of the JNTBGRI.

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