Natures wonders: butterflies can regulate eye spot size (Introduction)

by David Turell , Tuesday, February 11, 2020, 18:38 (1745 days ago) @ David Turell

In certain African butterflies:

https://phys.org/news/2020-02-butterflies-ability-eyespot-size.html

"The study reveals that the African satyrid butterfly Bicyclus anynana (B. anynana), a member of the sub-family of the nymphalidae (or 'brush-footed') butterflies, changes its eyespot size using a complex physiological and molecular response that evolved gradually over millions of years. The findings also highlight that while temperature modulates hormone levels in various species of satyrid butterfly, B. anynana is just one of a few that take advantage of this response to regulate eyespot size.

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"How butterflies accomplish this feat has only been studied in one species of African satyrid, B. anynana. In this species, low temperatures that signal the arrival of the dry season lower the quantity of a hormone called 20E during the late larval stage. This alters the function of hormone-sensitive cells in the centre of the eyespots and subsequently shrinks their size.

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"'We wanted to find out which other species change their eyespot size in response to temperature and whether they achieve this through the same mechanism as B. anynana. This comparative work would allow us to explore for the first time how a temperature-regulated system evolves at the genetic and physiological level."

"To do this, Bhardwaj and his team reared 13 different species of satyrid at two different temperatures. They found that all species had lower levels of the 20E hormone in response to low temperatures, but most of them were unable to change the size of their eyespots accordingly. This included species that are known to have different eyespot sizes during wet and dry seasons. "We also saw that a small group of species expressed the hormone receptor in their eyespot centres just like B. anynana, but this also was also not sufficient to shrink its size," says Bhardwaj.

"The team then manipulated the 20E hormone in four of the 13 species, and found that B. anynana is the only one to have evolved a temperature and hormone-mediated system of eyespot size regulation. They suggest that this species gradually evolved the ability to change its eyespot size according to temperature as a result of seasonal variations in its natural African habitat."

Comment: manipulating a complex hormone suggests design. 20E is complex: "20-Hydroxyecdysone (ecdysterone or 20E) is a naturally occurring ecdysteroid hormone which controls the ecdysis (moulting) and metamorphosis of arthropods. It is therefore one of the most common moulting hormones in insects, crabs, etc."

https://duckduckgo.com/l/?kh=-1&uddg=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2F20-Hyd...