Transparency in butterflies, from A-Z: It's more of a superpower than we thought

Date:
January 24, 2022
Source:
Marine Biological Laboratory
Summary:
Wing transparency as a flexible weapon for self-defense is one
of many findings from a multi-year study spanning the physics,
biology, ecology, and evolution of transparency in butterflies
conducted by several groups.



FULL STORY ==========================================================================
Like invisibility in legends, transparency in nature is a powerful
tool. Most transparent animals live in the ocean, where a close visual
match with the water renders them almost invisible to predators.


==========================================================================
On land, transparency is rare and difficult to achieve, but some
butterflies and moths (Lepidoptera) do have transparent wings. And a new
study indicates transparency can serve not only to camouflage them, but
in other cases to signal and warn predators, "Don't eat me! I'm toxic."
This flexible weapon for self-defense is one of many findings from a
multiyear study spanning the physics, biology, ecology, and evolution of transparency in Lepidoptera conducted by several groups, including the
lab of Nipam Patel, director of the Marine Biological Laboratory (MBL).

"This is one of those interdisciplinary studies you dream about, where
you want to understand [a biological structure] from its physics to its development and ecology," says Patel of the international study, which
began as a project in the MBL Embryology course and ended up being funded
by the Human Frontier Science Program. Ph.D. candidate Aaron Pomerantz
in Patel's lab is also on the team.

Mimicry for Self-Defense The group's latest paper adds a unique
perspective on Lepidoptera self-defense.

In some species, vivid wing coloration indicates the presence of chemical defenses that make the butterfly unpalatable or toxic, and predators
learn to avoid them. Accordingly, palatable species can evolve to
mimic the toxic ones, so predators leave them alone, too. In addition,
multiple unpalatable species may converge in their warning colorations,
thereby sharing in the benefits of the warning coloration process. Large "mimicry rings" can even form containing both toxic and nontoxic species,
all displaying strikingly similar patterns and color combinations.



==========================================================================
"The most amazing place to see this is the Amazon," Patel says. "You'll
find a group of species that are distantly related to each other, yet
they've all converged on a similar wing pattern." Surprisingly, mimicry
rings have also been found among clear-wing species in the Amazon. "So
we asked, 'Wait, why would a species be transparent and unpalatable at
the same time?'" Patel says. And, structurally, how would a clear-wing
species accomplish that trick? The team looked at the optical and
structural properties of transparent butterfly wings within mimicry
rings to see if they were convergent, and found in some rings, they were.

"In one transparency ring we studied (see photo 1, middle row),
the key unpalatable butterfly doesn't have an anti-glare coating on
its transparent wing, so in sunlight, it's really easy to see," Patel
says. "It may be signaling a warning pattern to predators when it's in
bright sun, and it's camouflaged when in shadows. So it kind of cheats:
it has the best of both worlds." Previously, the team reported on
the developmental origins of transparency in a clear-wing species,
Greta oto.They also compared wing transparency across 123 Lepidoptera
species for its structural basis, optical properties, and biological
relevance in relation to concealment, thermoregulation, and protection
against UV. Those results showed a wide diversity of solutions to achieve transparency, suggesting that transparency has likely evolved multiple
times independently.

Approaching transparency from multiple disciplines brought emergent
knowledge and interesting new questions, Patel said. "Now that we've
identified different Lepidoptera groups that have found different ways
to achieve transparency, we can ask, how did they actually do this? Or, alternatively, if two very distant lineages have come up with the same
solution for transparency, did they solve the problem in the same way?"
In addition to the MBL, collaborators in the initiative include scientists
from the University of California, Berkeley; University of Chicago;
California Institute of Technology; CNRS, France; Muse'um National
d'Histoire Naturelle, France; Sorbonne Universite', Paris, France;
Universite' des Antilles, France; Ecole Pratique des Hautes Etudes,
France; Ministe`re de la Culture, France; and Universite' de Montpellier, France.

========================================================================== Story Source: Materials provided by Marine_Biological_Laboratory. Original written by Diana Kenney. Note: Content may be edited for style and length.


========================================================================== Journal References:
1. Charline Sophie Pinna, Mae"lle Vilbert, Stephan Borensztajn,
Willy Daney
de Marcillac, Florence Piron-Prunier, Aaron Pomerantz, Nipam H
Patel, Serge Berthier, Christine Andraud, Doris Gomez, Marianne
Elias. Mimicry can drive convergence in structural and light
transmission features of transparent wings in Lepidoptera. eLife,
2021; 10 DOI: 10.7554/ eLife.69080
2. Doris Gomez, Charline Pinna, Jonathan Pairraire, Mónica Arias,
Jéro^me Barbut, Aaron Pomerantz, Willy Daney de Marcillac,
Serge Berthier, Nipam Patel, Christine Andraud, Marianne Elias. Wing
transparency in butterflies and moths: structural diversity, optical
properties, and ecological relevance. Ecological Monographs, 2021;
91 (4) DOI: 10.1002/ecm.1475
3. Aaron F. Pomerantz, Radwanul H. Siddique, Elizabeth I. Cash, Yuriko
Kishi, Charline Pinna, Kasia Hammar, Doris Gomez, Marianne Elias,
Nipam H. Patel. Developmental, cellular, and biochemical basis
of transparency in clearwing butterflies. Journal of Experimental
Biology, 2021; DOI: 10.1242/jeb.237917 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220124103848.htm

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