FEBRUARY 11, 2020
by eLife
New insight on how a butterfly
species developed the ability to adjust its wing eyespot size in response to
temperature has been published today in eLife.
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.
Many butterflies in the
nymphalidae family have circular eyespot patterns on their wings that are
typically used to deflect attacks from predators. However, in certain seasons,
such as the dry season in Africa, the butterflies' best survival strategy is to
avoid drawing attention to themselves, and they will shrink the size of their
eyespots to make them look like a dead leaf.
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.
"For our study, we
investigated how this hormone-mediated system came to regulate the size of
eyespots by examining the process in several other species of butterflies with
and without eyespots," explains lead author Shivam Bhardwaj, who conducted
this work as part of his doctoral research in the Department of Biological
Sciences at the National University of Singapore (NUS), and who is now a
postdoctoral fellow at Mississippi State University. "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."
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