Science

Rare biological phenomenon in dragonflies sighted at Kole wetlands

A female Scarlet Skimmer

A female Scarlet Skimmer  

Only 30 such individuals have been reported worldwide, says paper published in Journal of Threatened Taxa

When Renjith R.V and Vivek Chandran spotted a peculiar dragonfly, the Scarlet Skimmer (Crocothemis servilia), in the Puzhakkal area of the Kole wetlands in Thrissur last year, little did they know that they were documenting a very rare biological phenomenon.

Even though the dragonfly was perched in the deep marsh, Mr. Renjith managed to take a photograph of it. They were puzzled by its appearance as male dragonflies typically have prominent blood red colouraton in almost all their body parts, including the head, thorax, abdomen and legs, and the female is a pale yellow in colour with a dark brown thorax and legs.

A male Scarlet Skimmer

A male Scarlet Skimmer  

But the one they spotted on July 14 as part of the Kole Odonata Survey 2019, conducted by the Society for Odonate Studies and Kole Birders, in association with Kerala Agricultural University and the Kerala Forest and Wildlife Department, was “part red and part yellow”.

Later, while compiling data, they were thrilled to find that they had recorded gyanandromorphism — a very rare biological phenomenon. Their finding has been published in the latest issue of the Journal of Threatened Taxa under the title ‘A Record of Gynandromorphism in the Libellulid Dragonfly Crocothemis Servilia from India’.

‘Genetic aberration’

Gynandromorphs are chimeric individuals having both male and female tissues, and are viewed by the scientific community as a genetic aberration. Even though common in some arthropod taxa such as Crustacea and Arachnida, the paper says it is very rare in Odonates and only 30 individuals from seven families have been reported with the condition worldwide.

The spotted individual showed bilateral gynandromorphism of only the thorax, half of which showed blood red colouraton as in males, and the other half had the pale yellow characteristc of females. The base of the wing of the red half was marked with rich amber, in contrast with the other wing base, which was paler. The head, legs and abdomen showed typical female morphology.

The individual had a mix of male and female external characters, ranging from almost entirely female to about equally divided. “They were symmetrical in development with normally dimorphic structures mostly having characters intermediate between the typical male and female conditions,” the paper noted.

Further research has to be undertaken to investigate the infuence of environmental factors on this phenomenon, said Mr. Renjith, a school teacher in Palakkad, and Mr. Vivek, a Ph.D. scholar researching dragonflies.

The Society for Odonate Studies has been conducting Odonate surveys at the Kole wetlands since 2018, and 37 species of dragonflies and damselflies have been reported from the wetlands so far.

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Printable version | Jul 13, 2020 12:49:14 PM | https://www.thehindu.com/sci-tech/science/rare-biological-phenomenon-in-dragonflies-sighted-at-kole-wetlands/article31939658.ece

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